Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys
Two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%) and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam cold hearth melting approach—are employed in a present study as program materials. the influence of microstructure formed by means of the subs...
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Інститут металофізики ім. Г.В. Курдюмова НАН України
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| Zitieren: | Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys / O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V.A. Berezos, V.I. Bondarchuk, O.O. Stasyuk, P.E. Markovsky // Progress in Physics of Metals. — 2018. — Vol. 19, No 3. — P. 309-336. — Bibliog.: 37 titles. — eng. |
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nasplib_isofts_kiev_ua-123456789-1679142025-02-09T20:19:03Z Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys Вплив мікроструктури, способу та швидкости де формації на механічну поведінку стопів ti−6Al−4V і ti−1,5Al−6,8Mo−4,5Fe, виготовлених електронно-променевим топленням Влияние микроструктуры, способа и скорости деформации на механическое поведение сплавов ti–6Al–4V и ti–1,5Al–6,8Mo–4,5Fe, приготовленных электроннолучевой плавкой Ivasishin, O.M. Akhonin, S.V. Savvakin, D.G. Berezos, V.A. Bondarchuk, V.I. Stasyuk, O.O. Markovsky, P.E. Two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%) and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam cold hearth melting approach—are employed in a present study as program materials. the influence of microstructure formed by means of the subsequent thermomechanical and heat treatments on both the mechanical behaviour (evaluated by the deformation energy, UD) when tested using standard methods with different deformation rates and the ballistic resistance of plate materials is investigated. На прикладі двох промислових економно леґованих титанових стопів, — малолеґованого α + β-стопу ti–6Al–4V (мас.%) і метастабільного βстопу ti–1,5Al–6,8Mo–4,5Fe, — виготовлених одноразовим електроннопроменевим топленням з проміжною ємністю, вивчено вплив формованої за подальших (термомеханічного та термічного) оброблянь мікроструктури на механічну поведінку (виражену через енергію деформації UD) при випробуваннях з різними швидкостями деформації та балістичну стійкість. На примере двух промышленных экономно легированных титановых сплавов, — малолегированного α + βсплава Тi–6Al–4V (масс.%) и метастабильного βсплава ti–1,5Al–6,8Mo–4,5Fe, — приготовленных однократной электроннолучевой плавкой с промежуточной ёмкостью, изучено влияние формируемой при последующих (термомеханической и термической) обработках микроструктуры на механическое поведение (выраженное через энергию деформации UD) при ис пы таниях с разными скоростями деформации и баллистическую стойкость. Parts of this work were done within the frames of the projects ## III0913, 60/13c, and 60/16п funded by the National Academy of Sciences of Ukraine, and supported by the NAto grant G5030 from the Program ‘Science for Peace and Security’. 2018 Article Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys / O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V.A. Berezos, V.I. Bondarchuk, O.O. Stasyuk, P.E. Markovsky // Progress in Physics of Metals. — 2018. — Vol. 19, No 3. — P. 309-336. — Bibliog.: 37 titles. — eng. 1608-1021 DOI: https://doi.org/10.15407/ufm.19.03.309 PACS numbers: 61.66.Dk, 61.72.Ff, 61.72.Hh, 62.20.M-, 68.37.Hk, 68.55.jd, 81.05.Bx, 81.10.Fq, 81.20.Hy, 81.40.Ef, 81.40.Jj, 81.40.Np, 81.70.Bt, 83.50.Uv, 83.60.Pq https://nasplib.isofts.kiev.ua/handle/123456789/167914 en Успехи физики металлов application/pdf Інститут металофізики ім. Г.В. Курдюмова НАН України |
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Two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%) and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam cold hearth melting approach—are employed in a present study as program materials. the influence of microstructure formed by means of the subsequent thermomechanical and heat treatments on both the mechanical behaviour (evaluated by the deformation energy, UD) when tested using standard methods with different deformation rates and the ballistic resistance of plate materials is investigated. |
| format |
Article |
| author |
Ivasishin, O.M. Akhonin, S.V. Savvakin, D.G. Berezos, V.A. Bondarchuk, V.I. Stasyuk, O.O. Markovsky, P.E. |
| spellingShingle |
Ivasishin, O.M. Akhonin, S.V. Savvakin, D.G. Berezos, V.A. Bondarchuk, V.I. Stasyuk, O.O. Markovsky, P.E. Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys Успехи физики металлов |
| author_facet |
Ivasishin, O.M. Akhonin, S.V. Savvakin, D.G. Berezos, V.A. Bondarchuk, V.I. Stasyuk, O.O. Markovsky, P.E. |
| author_sort |
Ivasishin, O.M. |
| title |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys |
| title_short |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys |
| title_full |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys |
| title_fullStr |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys |
| title_full_unstemmed |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys |
| title_sort |
effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted ti-6al-4v and ti-1.5al-6.8mo-4.5fe alloys |
| publisher |
Інститут металофізики ім. Г.В. Курдюмова НАН України |
| publishDate |
2018 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/167914 |
| citation_txt |
Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys / O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V.A. Berezos, V.I. Bondarchuk, O.O. Stasyuk, P.E. Markovsky // Progress in Physics of Metals. — 2018. — Vol. 19, No 3. — P. 309-336. — Bibliog.: 37 titles. — eng. |
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Успехи физики металлов |
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ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 309
https://doi.org/10.15407/ufm.19.03.309
PACS numbers: 61.66.Dk, 61.72.Ff, 61.72.Hh, 62.20.M-, 68.37.Hk, 68.55.jd, 81.05.Bx, 81.10.Fq,
81.20.Hy, 81.40.Ef, 81.40.Jj, 81.40.Np, 81.70.Bt, 83.50.Uv, 83.60.Pq
o.M. iVaSiShin 1, S.V. akhonin 2, D.g. SaVVakin 1, V.a. berezoS 2,
V.i. bonDarChuk 1, o.o. StaSYuk 1, and P.e. MarkoVSkY 1
1 G.V. Kurdyumov Institute for Metal Physics, NAS of Ukraine,
36 Academician Vernadsky Blvd, UA-03142 Kyiv, Ukraine
2 Ye.O. Paton Electric Welding Institute, NAS of Ukraine,
11 Kazimir Malevich Str., UA-03150 Kyiv, Ukraine
effect of MicrostrUctUre, DeforMation
MoDe anD rate on Mechanical behaVioUr
of electron-beaM MelteD ti–6al–4V
anD ti–1.5al–6.8Mo–4.5fe alloys
two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%)
and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam
cold hearth melting approach—are employed in a present study as program materi
als. the influence of microstructure formed by means of the subsequent thermo
mechanical and heat treatments on both the mechanical behaviour (evaluated by
the deformation energy, UD) when tested using standard methods with different
deformation rates and the ballistic resistance of plate materials is investigated. As
revealed, the weakest dependence of UD on the strain rate corresponds to ti–6Al–4V
alloy with microstructure morphology close to globular one, whereas in the same
alloy with a lamellar microstructure (annealed in a singlephase βfield) as well as in
ti–1.5Al–6.8Mo–4.5Fe alloy with various microstructures, UD values significantly
depend on the rate of deformation. Moreover, only after annealing at a temperature
of the twophase α+β field, the UD value for ti–6Al–4V upon threepoint flexure at
varying deformation rate is equal to the sum of the corresponding values obtained
under tension and compression. During subsequent ballistic tests of plates of differ
ent thicknesses, it is established that the best ballistic impact resistance corresponds
to the materials with higher UD values and lower strainrate sensitivity. the dam
age of alloys during all types of testing is discussed in detail in terms of possible
mechanisms of deformation and fracture.
Keywords: titanium alloys, microstructure, mechanical properties, mechanical be
haviour, deformation rates, deformation energy, ballistic tests.
310 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
introduction
the titaniumbased alloys and coatings are a unique class of structural
materials for many applications, and first of all aerospace and military,
due to their high specific strength, fatigue endurance, resistances to
crack growth and corrosion [1–6]. In some cases, these materials are
employed in parts working at high stresses and tough operating condi
tions, particularly, in parts subjected to highrate deformations and
high strengths. For instance, similar service conditions will take place
in the new generation of civil supersonic aircraft [7, 8] as well as in a
wide range of products for military use [9, 10]. Application of titanium
alloys as armour material is an extreme case of their use from the view
point of mechanical properties. there is a large number of published up
to now works on the ballistic impact behaviour of different titanium al
loys tested with different types of projectiles [9–19], but only few of
them paid some attention to different types of microstructure, and no
unambiguous relationships between microstructure and ballistic proper
ties have been revealed [15, 18]. At the same time, in some previous
works, we showed the determining role of phase composition and micro
structure in the mechanical behaviour of various titanium alloys tested
with different deformation rates (quasistatic range) on tension, compres
sion and threepoint bending [20–22]. earlier [23, 24], ti–6Al–4V (wt.%)
alloy produced via singlemelt electronbeam with cold hearth melting
(ebCh) and then milled to assigned thickness without any final anneal
ing was recognized as the most appropriate titanium armour material
from the viewpoint of price/properties (or reliability) ratio.
the goal of this work was to evaluate real possibility to improve
mechanical behaviour under deformation with different rates, and, fi
nally, to enhance ballistic properties of two titanium costefficient al
loys ti–6Al–4V and ti–1.5Al–6.8Mo–4.5Fe (wt.%) (socalled ‘low cost
beta’) produced with abovementioned melting technique. to achieve
this goal, we used various types of subsequent heat treatment, which
allowed varying the structural and phase state of the alloys. With the
aim to evaluate possibility to obtain the best ballistic impact protection
properties, a special surface rapid heat treatment (Srht) was employed
for the both alloys that allowed forming gradient microstructure with
strengthened surface layer combined with a ductile core [25–27].
Materials and experimental Procedure
two above mentioned alloys were melted with ebCh melting approach
in the form of 100 mm diameter and about 200 mm long ingots, using
titanium sponge and Al–V master alloy (for ti–6Al–4V) or pure Al, Fe
and Mo (for ti–1.5Al–6.8Mo–4.5Fe). the ingots were melted at labora
tory electronic beam unit Ue208 [28] by single melting. real chemical
ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 311
Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
compositions of melted ingots (averaged for three different locations of
ingots) were as follow: (i) ti–5.8Al–3.86V and (ii) ti–1.6Al–6.3Mo–
4.36Fe (wt.%). the ingots were subjected to superficial turning and
subsequent 3D pressing with total reduction of about 60% at single
phase βtemperatures: starting temperature was 1100°C and 900°C for
the ti–6Al–4V and ti–1.5Al–6.8Mo–4.5Fe, respectively. In more de
tail, the melting and thermomechanical processing of ti–6Al–4V and
ti–1.5Al–6.8Mo–4.5Fe alloys were described in [29] and [30], respec
tively. After hot pressing, both alloys were rolled in standard mills at
temperatures of twophase α + β field: ti–6Al–4V at 880 °C to the final
thicknesses of 23 mm and 11 mm, and ti–1.5Al–6.8Mo–4.5Fe at 750 °C
to the thickness of 11 mm. Some rolled plates were annealed at different
temperatures of twophase α + β and singleβphase fields with aim to
obtain different types of microstructure. the Srht was performed at
special induction heating device developed at the G.V. Kurdyumov Insti
tute for Metal Physics of the National Academy of Sciences of Ukraine
[31]. All types and regimes of treatments employed in the present study
are listed in table 1. their application allowed us to obtain a wide range
of structural conditions, which varied in phase composition, type and
fineness of microstructure, and to form gradient states with hardened
surfaces combined with a ductile core.
Table 1. Treatments and microstructural states
## type of treatment regime of treatment Microstructure
ti–6Al–4V
1 hot deformation 3D hot pressing + rolling
at 880 °C
laminated, not recrystal
lized, unstable
2 Annealing
in the α + βfield
880 °C, 1 h,
furnace cooling
laminated, not recrystal
lized, stabilized
3 Annealing
in the βfield
1100 °C, 1 h,
furnace cooling
Coarsegrained lamellar
4 Surface rapid
heat treatment
80 kWt, 66 khz, 1000 A,
3 mm/s + aging 550 °C, 6 h
Gradient: hardened sur
face (UtS ≥ 1300 MPa
[29]), laminated core
ti–1.5Al–6.8Mo–4.5Fe
5 hot deformation 3D hot pressing + rolling at
750 °C
laminated, not recrystal
lized, unstable
6 Annealing
in the α + βfield
750 °C, 1 h,
furnace cooling
elongated βgrains, globu
lar α, stabilized
7 Quenching
from βfield
900 °C, 0.5 h,
water quenching
Singlephase metastable β
8 Surface rapid
heat treatment
80 kWt, 66 khz, 1000 A,
2.5 mm/s + aging 538 °C,
6 h
Gradient: hardened sur
face (UtS ≥ 1550 MPa
[30]), laminated α core
312 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
Microstructure of alloys after different treatments was examined
with light microscopy (lM) and scanning electron microscopy (SeM).
the SeM was also employed for investigation of fracture surfaces of
specimens after mechanical and ballistic tests. tensile properties were
studied in accordance with the AStM e8M standard on specimens with
gage length of 25 mm and gage diameter of 4 mm at INStroN3376
unit at different strain rates (quasistatic regimes). threepoint flexure
tests were done on bar samples with dimensions of 60×8×8 mm at IN
StroN 8802 unit. All specimens for mechanical tests were cut in roll
ing direction, and, at least, three specimens were tested for each micro
structural state and deformation rate. ballistic tests were performed in
the certificated laboratory at the Ivan Chernyakhovsky National Uni
versity of Defence of Ukraine using ballistic barrels and projectiles list
ed in table 2. the bullets had different calibres (diameters) and steel
cores (nonhardened soft (lPS) with hardness comparable to the hard
ness of tested titanium alloys, i.e. about 300–350 hV, or thermally har
dened (PP and b32) with hardness above 750 hV). Different bullet
masses and speeds allowed varying specific kinetic energy during tests.
ballistic tests were performed in accordance with Ukrainian Standards
b41032002 and 39752000.
results
Microstructure
typical microstructures of the alloys after different processing routes
are presented in Figs. 1 and 2. As seen from Fig. 1, hot deformation of
cast ti–6Al–4V alloy did not lead to recrystallization, and microstruc
ture was characterized by primary βgrains elongated in rolling direc
tion with fine αlamellas grown inside from grain boundaries (Fig. 1, a).
the thickness of these ‘flattened’ grains varied within the range of
20–100 µm due to intense and deep plastic deformation of initial cast
structure, in which the βgrain size reached several tens (or even hun
dreds) of millimetres [29]. Further annealing at 880 °C (this tempera
Table 2. Characteristics of projectiles used in ballistic tests
## Designation
bullet
Caliber, mm
bullet
Mass, g
type of core
Average
speed, m/sec
Specific kinetic
energy, J/mm2
1 PP 5.45 3.61 hardened steel,
ogival shape
915 ± 18 65 ± 4
2 lPS 7.62 9.62 Soft steel,
ogival shape
840 ± 27 78 ± 5
3 b32 7.62 10.4 hardened steel,
ogival shape
845 ± 20 82 ± 5
ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 313
Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
ture cor responds to the α + β field) did not changed both grain and in
tragrain microstructure in asrolled material (compare (Fig. 1, a and b),
but some βgrain boundaries (obviously, those with specific crystallo
graphic orientation) were decorated by lamellar (or platelike) αphase.
this allows concluding that the density of defects introduced by rolling
was not enough to initiate recrystallization even on subsequent anneal
ing at temperatures of α + β field. the increase in annealing tempera
ture up to 1100 °C (singlephase βfield for this alloy) naturally caused
intense βgrain growth, and relatively coarse and inhomogeneous βgrain
microstructure was formed with grain size varying from 50 to 500 µm
due to inheritance of nonuniformity of initial microstructure after an
nealing (Fig. 1, c).
After Srht, the alloy had layered structure (Fig. 1, d), in which
nearsurface upper layers had thickness of about 4 mm and consisted of
Fig. 1. Microstructure of ti–6Al–4V alloy in different states: a —
asrolled, b — after annealing at 880 °C for 2 h, c — after anneal
ing at 1100 °C for 1 h, and d — after Srht with lM
314 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
βtransformed microstructure formed as a result of α + β → β trans
formation during rapid heating and subsequent β → α (α′) + β decomposi
tion upon cooling [32].
ti–1.5Al–6.8Mo–4.5Fe alloy after hot deformation had laminated
microstructure without elongated βgrains (Fig. 2, a; initial cast micro
Fig. 2. Microstructure of ti–1.5Al–6.8Mo–4.5Fe alloy in different states: a — after
rolling and annealing at 750 °C for 2 h; b — after quenching from 900 °C into water
(metastable βstate); (c–e) — after Srht, where c — overall view, d — surface
layer, e — core. here, a, d, e — SeM; b, c — lM
ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 315
Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
structure of this alloy was discussed in detail earlier [30]). Subsequent
annealing at 750 °C, 2 h (twophase α + β field for this alloy) caused par
tial transformation of intragrain αphase from lamellar to globular one
(Fig. 2, b). It is important to underline that, in both cases, βgrain
boundaries were decorated by lamellar αphase, which is generally con
sidered as a structural element that embrittles titanium alloys [2]. the
application of Srht to this alloy, like in above mentioned case, also led
to formation of gradient microstructure (Fig. 2, c): the top layer (about
40 mm) undergone α + β → β transformation and consisted of βtrans
formed grains with diameter of 20–40 µm (Fig. 2, d), whereas deeper
layers had initial fine globularlike microstructure (Fig. 2, e).
standard Mechanical tests
In present work, we did tensile and threepoint flexure tests, while for
the discussion and evaluation of the influence of deformation mode and
rate on the mechanical behaviour of studied alloys we also used earlier
results of compression tests [22].
tensile tests
the mechanical behaviour of both alloys under tension in dependence on
their microstructure and tension rate was studied and discussed in de
tail in the previous work [21], including ti–6Al–4V and ti–1.5Al–
6.8Mo–4.5Fe alloys produced by standard vacuum arc (VAr) melting
and multistep deformation routes. It is necessary to underline once again
that, in the present study, we employed singlemelt ebCh alloy as start
ing material and subjected it to thermomechanical treatments described
in the second section (‘Materials and experimental Procedure’).
Fig. 3. typical engineering stress–strain curves of ti–6Al–4V alloy tested at diffe
rent strain rates after 1 h annealing at 880 °C (a) and 1100 °C (b)
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Ti–6Al–4V Alloy. typical en
gineering stress–strain curves of
ti–6Al–4V alloy were character
ized by sharp transition from elas
tic to plastic deformation (Fig. 3)
that is not typical for this alloy ob
tained by VAr melting [2, 29]. Af
ter α + β annealing (Fig. 1, b), the material had better combination of
strength and ductility (Fig. 3, a) as compared to annealing in the single
phase βfield (Fig. 3, b) which resulted to coarsegrained lamellar micro
structure (Fig. 1, c). Increase in strain rate led to reduction of elonga
tion for both structural conditions, but, in the latter case of coarse
grained lamellar microstructure, this reduction was bigger. After Srht,
the material was not tensile tested because it was impossible to machine
cylindrical samples adequately to obtain symmetrical twolayered mate
rial. however, in the earlier works, it was shown that surface treatment
of this alloy allows improving tensile properties up to the level similar
to that after bulk rapid heat treatment when tested with some standard
tension rate [27].
Calculated dependences of UD on tensile strain for different strain
rates (Fig. 4) showed essential difference between these two structural
states. First, it should be underlined that, in the material annealed at
the temperatures of twophase field, the UD value was higher and had
less pronounced dependence on strain rate as compared to the alloy an
nealed in the singlephase field.
Ti–1.5Al–6.8Mo–4.5Fe Alloy. the influence of tension rate on me
chanical behaviour of this alloy has been studied in detail in our previ
ous works [20, 21, 34]. In the present study, we took as a program
material a newly melted by singlemelt ebCh alloy which was subjected
to hot pressing and rolling as described in ref. [30]. this program mate
rial had specific microstructure features (Fig. 2) and crystallographic
texture as compared to earlier studied tIMetAllCb alloy of the same
composition, but melted by standard VAr technology [2] and subjected
to much heavier total deformation. typical engineering stress–strain
curves for our material are presented in Fig. 5. It is interesting to note
that, in both principally different conditions—twophase α + β fine glob
ular (Fig. 2, a) and singlephase metastable β (Fig. 2, b), this alloy had
very similar stress–strain curves at the same strain rates (compare
curves 1 and 2 on Fig. 5, a, with curves 1 and 3 on Fig. 5, b). this fact
Fig. 4. Dependences of deformation en
ergy on tension rate for ti–6Al–4V alloy
in different structural conditions: an
nealing at 880 °C (1) and 1100 °C (2)
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
is unexpected and may be explained
by very fine microstructure of the
alloy annealed at 750 °C.
the dependences of UD on strain
rate, calculated by tensile curves
for these two microstructural con
ditions, are presented in Fig. 6. they also showed similar decrease in
deformation energy with deformation rate. Such dependence is rather
typical for this alloy [20, 21, 34], and was explained by factors: (i) high
density of interphase α/β boundaries, which are sites of plastic defor
mation localization and nucleation of pores and cracks [34, 35] in an
nealed condition, and (ii) by specific crystallographic texture in metast
able condition, as it will be shown later.
A comparison of two materials from the viewpoint of dependences
of deformation energy on strain rate allows concluding as follows below.
the ti–1.5Al–6.8Mo–4.5Fe alloy in both annealed α + β and quenched
for metastable βphase states, despite higher initial (at 10−3 s−1) levels
of UD, is more sensitive to deformation rate as compared to ti–6Al–4V
alloy annealed in the twophase α + β field.
Fig. 6. Deformation energy vs. strain
rate for ti–1.5Al–6.8Mo–4.5Fe alloy in
two conditions: 1 — annealed in two
phase α+βfield; (2 — quenched from
βfield (metastable singlephase condi
tion)
Fig. 5. typical engineering stress–strain curves of ti–1.5Al–6.8Mo–4.5Fe alloy
tested at various strain rates in different microstructural states: a — after anneal
ing 750 °C for 1 h; b — after water quenching from 900 °C
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three-Point flexure
Ti–6Al–4V Alloy. the overviews of specimens after threepoint flexu
ral tests are presented in Fig. 7. As seen, the material with coarse
grained lamellar microstructure cracked on earlier stages of plastic de
formation (specimens 1 and 2), while, in the specimen with globular
microstructure, crack appeared on later stage of plastic flow when de
formed at lower bending rate (specimen 3).
the flexural stress–strain curves illustrate essential superiority of
the material annealed in the twophase α+β field over the coarsegrained
lamellar condition in both strength and especially ductility: the lami
nated microstructure after α+β annealing had approximately 6 times larger
plastic deformation (compare Fig. 8, a and b). Gradient microstructure
after Srht (Fig. 1, d) led to specific changes in flexure properties of
the alloy: the curves look like a combination of the first two versions—
strength level approached to the α+β annealed condition, while strains
were intermediate between these two structural states (Fig. 8, c).
Investigation of microstructure in the zones of intensive plastic
deformation allowed clarifying the features of the influence of micro
structure on mechanical behaviour during flexural testing (Fig. 9). In
the case of coarsegrained lamellar microstructure, main crack propa
gated from the bottom surface (where tension stress on flexure was
maximal) almost normally to this surface with rather small branching
(Fig. 9, a). the starting short crack was nucleated and grew initially
along a packet of αlamellas (Fig. 9, b). At further, propagation crack
was deviated on boundaries of neighbouring αphase packets with dif
ferent crystallographic orientations (Fig. 9, c).
At the same time, after annealing at temperature of twophase field,
there were no coarse equiaxed βgrains and intragrain αlamellas, and
the main crack initially grew at an angle of 45° to the bottom surface
and changed the direction of growth when achieved length of approxi
mately 3 mm (Fig. 9, d). there was no noticeable effect of microstructure
on crack propagation; however, at higher magnifications plenty of pores
were observed around crack on the etched surface of the specimens (Fig. 9,
e, f ). the specimens after Srht were not completely fractured at max
imal bend angle, and cracks stopped at distance of 2–3 mm from the
thermally strengthened layer (Fig. 9, g): final cracks were shorter as
Fig. 7. overviews of ti–6Al–4V spe
cimens after (1, 2) βannealing (1100 °C,
1 h), and (3, 4) α + β annealing (880 °C,
2 h), tested for threepoint bending with
rates (1, 3) 10−3 s−1 and (2, 4) 10−1 s−1
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
compared to other structural conditions for the same rates and degrees
of deformation. In the ‘basic’ nonhardened layer, the main crack sev
eral times changed direction and propagated mainly along the bounda
ries of neighbouring αphase packets (Fig. 9, h), while on the last stage
the crack crossed both these packets and individual αlamellas (Fig. 9, i).
Ti–1.5Al–6.8Mo–4.5Fe Alloy. At higher flexure rate, all ti–1.5Al–
6.8Mo–4.5Fe specimens, in both α + β annealed and as quenched from
single βphase conditions, were broken on the stage of elastic deforma
tion (Fig. 10). only metastable β specimens tested at lower flexure rate
had nonzero ductility; and this behaviour is opposite to ti–6Al–4V al
loy. Investigation of fracture surfaces of annealed specimens allowed
distinguishing three separate zones: 1 — crack nucleation and initial
growth, 2 — intensive growth zone, and 3 — final fracture (Fig. 11, a).
the overview of the first zone (indicated by arrow on Fig. 11, a, b) re
vealed that crack appeared in subsurface layer and initially grew by
ductile mechanism. however, when crack length reached about 30 µm,
the character of crack growth changed to a brittle one, and layered frac
ture surface was observed in this zone (2 in Fig. 11, a and c).
Fig. 8. Flexural stress–strain cur
ves after threepoint bending of
ti–6Al–4V specimens after а —
annealing at 1100 °C (coarsegrained
lamellar microstructure), b — an
nea ling at 880 °C, and c — Srht.
Fle xure rates: 10−3 s−1 (1) and
10−1 s−1 (2)
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Fig. 10. Flexural stress–strain curves
for ti–1.5Al–6.8Mo–4.5Fe alloy in α +
+ β annealed and metastable β states
tested with different rates
Fig. 9. Microstructure of ti–6Al–4V alloy after annealing 1 h at various tempera
tures and threepoint flexural testing: (a–c) 1100 °C (coarsegrained lamellar state),
(d–f) — 880 °C, and (g–i) — after Srht. SeM data
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
Fracture surfaces of the specimens in singlephase metastable β
state did not have evident signs of crack nucleation sites (Fig. 11, d).
both initial zone of crack growth (perpendicular to the outer surface of
specimen) and zone of intensive propagation (parallel one) had the same
character characterized by mixture of ductile and brittle (cleavage) ar
eas (Fig. 11, d) that was earlier observed in this alloy upon tensile tests
[34] and explained by specific orientations of βgrain boundaries rela
tively to direction of applied tension stress. on the boundaries of cleav
age areas (presumably, grain boundaries), a relief similar to lamellar
intragrain microstructure was observed (Fig. 11, f ). In the zone of final
fracture, character of surface was ductile (Fig. 11, f ).
Summarizing the results of tensile and threepoint flexural tests, it
is possible to conclude that only ti–6Al–4V alloy in annealed α + β state
demonstrated ductile behaviour in both types of tests. this is obviously
Fig. 11. Fracture surfaces of ti–1.5Al–6.8Mo–4.5Fe
specimens in (a–c) α + β annealed and (d–g) metastab
le β states, after threepoint flexure with rate 10−1 с−1.
Arrow (а) shows crack nucleation site. SeM data
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due to comparatively large area of uniform plastic deformation (Figs. 3,
a, and 8, b), while in another structural condition (Fig. 3, b) this alloy,
as well as ti–1.5Al–6.8Mo–4.5Fe alloy (Figs. 5 and 10) underwent ear
ly localization of plastic deformation, that caused much earlier failure.
ballistic impact tests
Ti–6Al–4V Alloy: 11 mm Thick Plate. the 11 mm thick plate of
ti–6Al–4V alloy was subjected to ballistic tests with two types of pro
jectiles, which differed in calibre, mass, state of steel core, speed of
bullets, and therefore had different specific kinetic energies (see ## 1
and 2 in table 2). the overviews of tested plates with different micro
structural states are shown in Fig. 12. As seen, in asrolled (without
final heat treatment) condition, the plate was pierced by 7.62 calibre
lPS bullet, and withstood a bullet of 5.45 calibre (Fig. 12, a, b). the
behaviour of plate annealed at twophase α + β field temperature was
very similar (Fig. 12, c and d), while, after annealing at singlephase β
temperature (with resulting coarsegrained lamellar microstructure,
βannealing at 1100 °C for 1 h, (e, f ) — after α + β annealing at 880 °C for 2 h, and
(g, h) — after Srht (surface strengthening). here, front (a, c, e, g) and back (b, d,
f, h) — views are presented. A — results of impact by bullets #1, B — results of
impact by bullets #2
Fig. 12. overview of 11 mm
thick ti–6Al–4V pla tes
after ballistic tests with
front (a, c, e, g) and back
(b, d, f, h) views for dif
ferent conditions: (a, b) —
as r olled, (c, d) — after
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
Fig. 13. SeM images for half sections of shot targets (a, d, g, j) and typical micro
structure of ti–6Al–4V alloy (11 mm thick plate) after ballistic tests: (a–c) — as
rolled, (d–f) — annealed at 880 °C for 1 h, (g–i) — annealed at 1100 °C, and (j–l) —
after Srht. PP bullets (#1 in table 2)
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Fig. 1, c), the plate was pierced by bullets of both types (Fig. 12, e, f ).
In other words, 11 mm thick plates of ti–6Al–4V alloy with both lami
nated microstructural states showed rather good resistance against pen
etration of bullets with average specific kinetic energy ≈65 J/mm2, and
could not stand against bullets with energy ≈78 J/mm2. At the same
time, the plate with βtransformed coarsegrained lamellar microstruc
ture was not able to resists against even bullets with lower energy.
the most promising result for 11 mm thick plate was obtained in
asrolled condition with subsequent special Srht; this plate was not
pierced by both types of bullets (Fig. 12, g and h) that is in a good agree
ment with the results of threepoint flexure tests (Figs. 8, c, and 9, h, i).
In other words, the surface strengthening treatment allows obtaining a
condition with higher ballistic resistance, and the present results are
apparently better than the data obtained in J. Fanning’s work [9]. the
Fig. 14. SeM images for half sections of shot targets
(a, d, g) and typical microstructure of ti–6Al–4V
alloy (11 mm thick plate) after ballistic tests: (a–c) —
asrolled, (d–f) — annealed at 880 °C for 1 h,
(g, h) — annealed at 1100 °C for 1 h. lPS bullets
(#2 in table 2)
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
Fig. 15. overview of ti–6Al–4V alloy (23 mm thick plates) after ballistic tests with
projectile #3 (table 2, bullets b32) for different conditions: (a, b) — after
βannealing at 1100 °C for 1 h), (c, d) — after α + β annealing at 880 °C for 2 h, and
(e, f ) — after Srht
peculiarities of plastic flow were studied on the sections cut from the
sites impacted by bullets (Fig. 13).
In the asrolled specimen (Fig. 13, a), separate adiabatic shear bands
(ASb) with thickness of about 10–12 µm were observed on the lateral
sides of the bullet channel (Fig. 13, b), while, in the lower part of the
crater, a βtransformed microstructure was found (Fig. 13, c; the depth
of this βtransformed layer was about 2 mm). this may be explained by
intensive local heating of the material above betatransus, i.e. an essen
tial part of kinetic energy transformed into a heat. Annealing at the
temperature of α + β field made material ‘weaker’; it was pierced by this
type of projectile (Fig. 13, d). Several ASb were observed near the mid
dle section of the bullet channel (Fig. 13, e), and, in some places, pores
appeared inside the ASbs (Fig. 13, f ). After annealing at the tempera
ture of βfield, the material was also pierced, and coarse cracks appeared
around the bullet channel where the bullet punched material (Fig. 13,
g). In upper part of the channel, no evidences of plastic deformation
were found (Fig. 13, h), while, in the bottom zone, multiple ASbs in
clined at an angle of more than 45° were observed (Fig. 13, i). After
Srht, the plate was not pierced by bullet (Fig. 13, j), and ASbs paral
lel to the surface were found near the middle section of the channel
(Fig. 13, k) as well as in the ‘deep bottom’ — on the distance more than
3 mm from the channel tip (Fig. 13, l).
Figure 14 illustrates similar features of plates’ microstructures af
ter shooting by lPS bullets (#2 in table 2). First of all, it should be
mentioned that all microstructures (except after surface strengthening
by Srht) were pierced by this relatively highenergy projectile (see
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table 1), and bullet channels looked like punching out a ‘cork’ (Fig. 14,
a, d, g). Due to high localization of plastic deformation, the flow oc
curred in the material adjacent to the bullets channels, that led to the
formation of cracks (Fig. 14, b, c), and only in some cases ASbs were
observed (Fig. 14, f ). besides, it should be mentioned that, in most duc
Fig. 16. SeM images for
half sections of shot tar
gets (a, d, g) and typical
microstructure of ti–6
Al–4V alloy (23 mm thick
plate) after ballistic tests:
(a–c) — after βannealing
at 1100 °C for 1 h, (d–f) —
after α + β annealing at
880 °C for 2 h, and (g–i) —
after Srht
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
tile condition (after annealing at α + β temperature), some traces of
plastic flow were found close to the bullet channel (Fig. 14, e), while, in
less ductile one (after annealing at βtemperature; Fig. 14, h), fracture
took place without any visible changes in microstructure. At the same
time, in Srhttreated plate, which was not pierced (Fig. 12, g, h), the
traces of deformation were similar to those observed for projectile #1
(Fig. 13, k, l).
Ti–6Al–4V Alloy: 23 mm Thick Plate. the overviews of specimens
shot with projectiles b32 are shown in Fig. 15. As seen, the material
after annea ling at the temperature of singlephase βfield with coarse
grained lamellar microstructure was completely pierced, and the bullet
was stuck in the plate (Fig. 15, a, b). In two other structural states after
annealing at α + β temperature (Fig. 15, c, d) and after Srht (Fig. 15,
e, f ), the plates were not penetrated through, and the ‘bulge’ effect was
noticeab ly less pronounced in the case of Srht. these observations are
in a good agreement with the results obtained for 11 mm thick material
after the same treatments, and they confirm the positive influence of
both annealing at temperatures below the βtransus and surface strength
ening treatment.
(c, d, g, h) #2, and (e, f ) #3 for two conditions: (a–f ) — after α + β annealing at
750 °C for 2 h and (g, h) — after Srht streng thening
Fig. 17. overview of
11 mm thick plates of
ti–1.5Al–6.8Mo–4.5Fe
alloy after ballistic tests
with projectiles (a, b) #1,
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In more detail, the microstructure of the plates near the bullet
channels is shown in Fig. 16. After annealing at 1100 °C, the material
with coarsegrained lamellar microstructure was punched through (Fig.
16, a). there were no noticeable traces of plastic deformation near the
edges of bullet channel (Fig. 16, b); separate ASbs were found near the
bottom of the channel (where the bullet has already lost most of its en
ergy), and these ASbs end by surface cracks (Fig. 16, c).
After annealing in twophase α + β field, the material had another
type of βgrain structure and was also pierced through; however, the
bullet was completely stopped inside the plate (Fig. 16, d). Near the top
of the bullet channel, some deformation traces were found (Fig. 16, e),
and, in the bottom, ASbs and cracks were present as well (Fig. 16, f).
Fig. 18. half sections of
shot targets (a, e, g), de
tails of fracture surfaces
and typical microstruc
tu re of 11 mm thick pla
tes of ti–1.5Al–6.8Mo–
4.5Fe alloy after ballis
tic tests with projectiles
#1 (a, b), #2 (c, d, e, f ),
and #3 (g, h) for two conditions: after α + β annealing at 750 °C for 2 h (a–d) and
after Srht strengthening (e–h). here, the SeM data are presented
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
After Srht, the bullet did not penetrate through the plate, and a bulge
of about 2–2.5 mm height formed on the rear side (Fig. 16, g). the
ASbs were observed both on the top (Fig. 16, h) and bottom (Fig. 16, i)
sections that indicates on the localization of plastic flow in both top
(thermally hardened) and bottom (ductile) layers. In other words,
hardened by Srht, layer had relatively good reserve of general ducti
lity, despite its higher strength, and its level of ductility was rather
close to that of the material annealed at temperatures of α + β field,
whereas the alloy with coarsegrained lamellar microstructure had too
low properties.
Fig. 19. Deformation energy vs. deformation rate at different types of tests for a —
ti–6Al–4V annealed at temperature of singlephase β field, b — ti–6Al–4V an
nealed at temperature of twophase α + β field, c — ti–1.5Al–6.8Mo–4.5Fe quenched
from temperature of singlephase β field (finegrained metastable β state), d —
ti–1.5Al–6.8Mo–4.5Fe annealed at temperature of twophase α + β field. Data for
compression tests were taken from [23]. open ‘star’ symbols on (a, b) indicate re
sults with complete piercing of plates. Solid ‘star’ symbols (b, d) indicate results of
ballistic tests without piercing
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Ti–1.5Al–6.8Mo–4.5Fe. typical examples of 11 mm thick plates of al
loy ti–1.5Al–6.8Mo–4.5Fe in different microstructural states after bal
listic tests are presented in Fig. 17. First of all, it should be underlined
that, after annealing in twophase α + β field, the material was not
punched through by bullets of #1 type, however, some surface cracks
appeared (Fig. 17, a and b), while higher specific kinetic energies (bul
lets #2 and #3) caused cracking (Fig. 17, c–f ). Application of Srht
allowed somewhat to improve ballistic resistance of the alloy against
projectiles #2 (Fig. 17, g and h), whereas bullets #3 still punched
through the plates.
In more detail, the fracture surfaces of the plates after ballistic
tests are shown in Fig. 18. After annealing in α + β field and impact by
projectile #1, the bullet channel had relatively ductile relief (Fig. 18, a,
b), while impact by more powerful projectile #2 led to completely brittle
fracture (Fig. 18, c and d). Another situation was observed in specimens
after Srht: despite impact with projectile #2 also led to brittle frac
ture (Fig. 19, g and h), projectile #1 caused only crater in the surface
strengthened layer (Fig. 18, e and f ).
Discussions
Under threepoint flexure, the upper part of sample (where bending
force is applied) is compressed and the opposite side is stretched, with a
zeroload point located approximately in the middle between them.
hence, in the first approximation, we can assume that this type of test
is a combination of stretching and compression tests. thus, it can be
assumed that the energy of deformation UD, which is spent on the three
point bend, should be approximately equal to the sum of these energies
for two tests—tension and compression. experimental data for compres
sion, obtained with the same program materials, were taken from the
work [24]. the dependences of UD on deformation rate for the same ma
terials and different methods of tests are represented in Fig. 19.
As can be seen from Fig. 19, this assumption is rather accurate for
the case of ti–6Al–4V annealed in twophase α+β field (880 °C, Fig. 19,
a). It should be also mentioned that similar situation was observed in
the same alloy with globular type of microstructure, and in commercial
purity titanium regardless of microstructure [26]. At the same time,
ti–6Al–4V and ti–1.5Al–6.8Mo–4.5Fe alloys annealed in singlephase
βfiled (coarsegrained lamellar microstructure) have different behav
iour (Fig. 19, b–d). earlier in [26], this fact was explained by the influ
ence of other factors, including structural and crystallographic texture.
Also, as it was established in ref. [21], lamellar or needlelike αparticles
play an important role in mechanical behaviour of titanium alloys de
formed with different rates, because their tips are places where defor
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Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
mational defects concentrate during plastic flow, leading to the forma
tion of pores and then cracks.
Another moment to be emphasized is the following: ti–1.5Al–
6.8Mo–4.5Fe in metastable singlephase βcondition had high ductility
that resulted in high UD values under tension and compression, while
for threepoint flexure this parameter was rather high only for rela
tively slow deformation rate (Fig. 19, c). Perhaps, this is a result of
probable decomposition of metastable βphase during the complex mode
of deformation (and possible precipitation of embrittling particles of
ωphase, especially, taking into account local heating inside ASbs formed
at high deformation rates). regarding this alloy in the twophase α + β
state, UD values for threepoint flexure were much lower than for ten
sile and compression tests. this is obviously due to the peculiarities of
microstructure (the presence of thin lamellar particles of αphase whose
tips play abovementioned role of stress concentrators) and the crystal
lographic texture formed upon rolling, which may be unfavourably ori
ented relative to the applied load.
the results of present study and previous data allow us to conclude
that the UD values of investigated alloys generally are determined by
their phase composition, microstructure, and structural and crystallo
graphic texture, which, in turn, determine the balance between strength
and ductility, and this balance depends on deformation mode and rate
too. thereby, relatively lowalloyed ti–6Al–4V alloy with globular
(equiaxed) microstructure has rather high values of ductility. however,
hardening of this alloy by heat treatment cannot ensure high strength;
in the best case after special rapid heat treatment (bulk), UtS does not
exceed 1300–1350 MPa [22, 27]. At the same time, metastable βalloy
ti–1.5Al–6.8Mo–4.5Fe can be thermally strengthened above 1500 MPa,
but high content of βalloying elements and relatively low betatransus
(temperature of α + β0 → β transformation [3]) do not allow to form equi
axed microstructure with αglobules of, at least, 2–3 µm in diameter
and relatively low (as in ti–6Al–4V alloy) density of interphase α/β
boundaries which are preferable sites for pore and crack nucleation dur
ing plastic flow [21]. these features caused low ductility of thermally
strengthened ti–1.5Al–6.8Mo–4.5Fe alloy, which may be improved by
means of special treatment based on heavy cold deformation followed by
rapid recrystallization for forming fine βgrains (below 5–7 µm) [22,
36]. Such technological approach was employed for rod materials, but
its application for processing of plate material (taking into account the
possibility of technological equipment) seems quite problematic. As
shown in refs. [22, 37], the best combination of high strength (above
1800 MPa) and good ductility can be obtained by rapid heat treatment
of such titanium alloy as Vt23 (highalloyed martensitic class alloy),
where the content of βalloying elements is ‘intermediate’ between ti–
332 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
6Al–4V and ti–1.5Al–6.8Mo–4.5Fe. In this case, it is possible to expect
that UD will be higher, including high deformation rates.
of course, the results of standard mechanical tests are difficult to
compare with the results of ballistic ones. Nevertheless, employing such
rather versatile parameter as UD and calculating (with some simpli
fications) its values for ballistic tests basing on the speed of the bullet,
its calibre and the thickness of tested plate, we tried to fulfil this com
parison. though this approach is rather arbitrary, it allows to assess
the ballistic resistance of materials considering the relation between UD
values for the same deformation rates obtained in ballistic tests and, if
possible, by other standard methods. In other words, if UD
ballistic >
> UD
Standard, material will be pierced, and if UD
ballistic < UD
Standard, material
will resist against ballistic impact. An attempt to make such a compari
son is presented in Fig. 19, a, b, d, where the results of ballistic tests
are plotted by ‘star’ symbols. First of all, it should be noted that an
increase in strain rate by four orders of magnitude reduces UD levels
also by several orders. Despite the significant difference between UD
levels of studied alloys at low deformation rates, at rates 8·104–8.2·104
(these values were calculated for ballistic tests), deformation energy
varied within the narrow range of 5.7–7.4 J/mm3, and difference be
tween pierced and not pierced microstructural states was also very
small. It should be kept in mind that, in this comparison, we did not
take into account the influence of all other factors besides kinetic en
ergy (e.g., the different hardness of bullets and test material). by the
way, our results showed some superiority of alloys after annealing in
twophase α + β field and Srht over the same materials with βtrans
formed lamellar microstructure.
conclusions
the obtained results allow drawing the following conclusions.
(1) the studied alloys obtained by ebMCh melting approach with
following hot 3D pressing and rolling had better properties (both stand
ard mechanical at all deformation rates and modes, and ballistic im
pact properties) after annealing at temperatures of twophase α + β field.
In this condition, ti–6Al–4V alloy had microstructure with flat β
grains elongated in rolling direction and fine αlamellas inside these
grains, while ti–1.5Al–6.8Mo–4.5Fe alloy had fine globulartype
microstructure.
(2) Annealing in singlephase βfield resulted in coarsegrained la
mellar microstructures and led to a significant decrease in all mecha
nical properties due to essential drop of ductility.
(3) Special Srhtreatment, which formed thermally strengthened
surface layer in combination with ductile core, allowed achieving the
ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 333
Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
best level of ballistic impact properties as compared to other micro
structural conditions studied in the present work.
(4) Good antiballistic properties of ti–6Al–4V alloy can be ex
plained by a unique combination of properties (of about 1000 MPa) with
high reserve of ductility (including high uniform plastic deformation in
notcoarsegrained lamellar state). this properties balance can be ob
tained even after singlemelt ebCh melting followed by hot deforma
tion (rolling) without any final annealing. At the same time, ti–1.5Al–
6.8Mo–4.5Fe alloy, despite of ability to obtain very high strength (not
less than 1500 MPa), is characterized by relatively poor ductility, and
first of all, small stage of uniform plastic deformation with early start
of localized plastic flow, especially, at increase of deformation rate.
(5) For a higher efficiency of surface hardening treatment in order
to form a gradient microstructure with increased antiballistic proper
ties, attention should be paid to alloys with an intermediate (between
ti–6Al–4V and lCb alloys) content of alloying elements. these alloys
have two benefits: (i) a welldeveloped globular microstructure can be
formed by annealing at α + β temperature; (ii) surface rapid heat treat
ment allows achieving strength levels ≥1500 MPa.
Acknowledgments. Parts of this work were done within the frames
of the projects ## III0913, 60/13c, and 60/16п funded by the Na
tional Academy of Sciences of Ukraine, and supported by the NAto
grant G5030 from the Program ‘Science for Peace and Security’.
reFereNCeS
I. Weiss, r. Srinivasan, P.J. bania, D. eylon, and S.l. Semiatin, 1. Advances in
the Science and Technology of Titanium Alloy Processing: Proc. Int. Symposium
Sponsored by the TMS Titanium and Shaping and Forming Held at the 125th
TMS Annual Meeting and Exhibition in Anaheim (California, February 5–8,
1996) (Warrendale, PA: tMS: 1997).
G. luetjering and J.C. Williams, 2. Titanium (berlin: SpringerVerlag: 2007).
r.r. boyer and r.D. briggs, 3. J. Mater. Eng. Perform., 14, Iss. 6: 681 (2005).
l.o. Chirkina, M.b. lazareva, V.I. Sokolenko, V.S. okovyt, and V.V. Kalynovsky, 4.
Usp. Fiz. Met., 17, No. 4: 343 (2016).
A.D. Pogrebnjak, o.M. Ivasishin, and V.M. beresnev, 5. Usp. Fiz. Met., 17, No. 1:
1 (2016).
V.e. Gromov, K.V. Sosnin, Yu.F. Ivanov, and o.A. Semina, 6. Usp. Fiz. Met., 16,
No. 3: 175 (2015).
See 7. https://boomsupersonic.com.
M. Prampolini and Y. Coraboeuf, 8. Ultra-Rapid Air Vehicle and Related Method for
Aerial Locomotion: United States Patent No. 9079661b2 (Published July 14, 2015).
J. Fanning, 9. J. Mater. Eng. Perform., 14, Iss. 6: 686 (2005).
J.S. Montgomery and M.G.Y. Wells, 10. JOM, 53, Iss. 4: 29 (2001).
J. Fanning, 11. Proc. of the 11th World Conference on Titanium) (June 3–7, 2007,
Kyoto, Japan) (Kyoto: the Japan Institute of Metals: 2007), p. 487.
C. zheng, F. Wang, and X. Cheng, 12. Int. J. Impact Eng., 85: 161 (2015).
334 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
M.S. burins, J.S. hansen, J.I. Paige, and P.C. turner, 13. The Effect of Thermo-
Mechanical Processing on the Ballistic Limit Velocity of Extra Low Interstitial
Titanium Alloy Ti–6Al–4V (Army research laboratory report ArlMr486:
July 2000).
b.b. Singh, G. Sukumar, A. bhattacharjee, K.S. Kumar, t.b. bhat, and A.K. Go14.
gia, Materials and Design, 36: 640 (2012).
C. zheng, F. Wang, X. Cheng, K. Fu, J. liu, Y. Wang, t. liu, and z. zhu, 15.
Mater. Sci. Eng.: A, 608: 53 (2014).
K. Sun, X. Yu, C. tan, h. Ma, F. Wang, and h. Cai, 16. Mater. Sci. Eng.: A, 595:
247 (2014).
G. Sukumar, b.b. Singh, A. bhattacharjee, K.S. Kumar, and A.K. Gogia, 17. Int.
J. Impact Eng., 54: 149 (2013).
C. zheng, F. Wang, X. Cheng, J. liu, K. Fu, t. liu, z. zhu, K. Yang, M. Peng, 18.
and D. Jin, Int. J. Impact Eng., 85: 161 (2015).
t.l. Jones, 19. Ballistic Performance of Titanium Alloys: Ti–6Al–4V Versus Rus-
sian Titanium (Army research laboratory report ArlCr0533: February
2004).
P.e. Markovsky, V.I. bondarchuk, and o.M. herasymchuk, 20. Mater. Sci. Eng.: A,
645: 150 (2015).
P.e. Markovsky and V.I. bondarchuk, 21. J. Mater. Eng. Perform., 26, Iss. 7: 3431
(2017).
P.e. Markovsky, Mechanical behavior of titanium Alloys under Different Con22.
ditions of loading, Key Eng. Mater., 2018 (in press).
J.S. Montgomery, M.G.h. Wells, b. roopchand, and J.W. ogilvy, 23. JOM, 49,
Iss. 5: 45 (1997).
J.S. Montgomery and M.G.h. Wells, 24. JOM, 53, Iss. 4: 29 (2001).
P.e. Markovsky and S.l. Semiatin, 25. J. Mater. Process. Technol., 210, Iss. 3: 518
(2010).
P.e. Markovsky, 26. Key Eng. Mater., 436: 185 (2010).
P.e. Markovsky and S.l. Semiatin, 27. Mater. Sci. Eng.: A, 528, Iss. 7–8: 3079
(2011).
S.V. Akhonin, V.А. berezos, А.N. Pikulin, А.Yu. Severin, and А.G. Yerokhin, 28.
Sovrem. Elektrometall., No. 1: 10 (2017) (in russian).
A.N. Kalinyuk, N.P. trigub, V.N. zamkov, o.M. Ivasishin, P.e. Markovsky, 29.
r.V. teliovich, and S.l. Semiatin, Mat. Sci. Eng.: A, 346, Iss. 1–2: 178 (2003).
S.V. Akhonin, P.e. Markovsky, V.А. berezos, o.o. Stasyuk, and А.Yu. Seve30.
rin, Sovrem. Elektrometall., No. 1: 9 (2018) (in russian).
See 31. https://www.imp.kiev.ua/download/development/MVI_1884.MoV.
o.M. Ivasishin and P.e. Markovsky, 32. JOM, 48, Iss. 7: 48 (1996).
o.M. Ivasishin, P.e. Markovsky, Yu.V. Matviychuk, and P. Allen, 33. Proc. of the
9th World Conf. Titanium’99: Science and Technology (St.Petersburg, russia,
CrISM ‘Prometey’: 2000), vol. 1, p. 505.
P.e. Markovsky, V.I. bondarchuk, and Yu.V. Matviychuk, 34. Mater. Sci. Eng.: A,
559: 782 (2013).
P.e. Markovsky, V.I. bondarchuk, o.V. Shepotinnyk, and I.M. Gavrysh, 35. Metal-
lofiz. Noveishie Tekhnol., 38, No. 7: 935 (2016).
Q.V. Viet, A.A. Gazder, P.e. Markovsky, A.A. Saleh, o.M. Ivasishin, and e.V. Pe36.
reloma, J. Alloys and Compounds, 585: 245 (2014).
P.e. Markovsky, 37. Metallofiz. Noveishie Tekhnol., 31: 511 (2009).
received July 10, 2018;
in final version, July 26, 2018
ISSN 1608-1021. Usp. Fiz. Met., 2018, Vol. 19, No. 3 335
Effect of Microstructure, Deformation Mode and Rate on Titanium Alloys
О.М. Івасишин 1, С.В. Ахонін 2, Д.Г. Саввакін 1, В.О. Березос 2,
В.І. Бондарчук 1, О.О. Стасюк 1, П.Є. Марковський 1
1 Інститут металофізики ім. Г. В. Курдюмова НАН України,
бульв. Академіка Вернадського, 36, 03142 Київ, Україна
2 Інститут електрозварювання ім. Є. О. Патона НАН України,
вул. Казимира Малевича, 11, 03150 Київ, Україна
ВпЛИВ мІКРОСтРуКтуРИ, СпОСОбу тА шВИДКОСтИ
ДЕфОРмАЦІї НА мЕхАНІчНу пОВЕДІНКу СтОпІВ
Ti−6Al−4V І Ti−1,5Al−6,8Mo−4,5Fe, ВИгОтОВЛЕНИх
ЕЛЕКтРОННО-пРОмЕНЕВИм тОпЛЕННЯм
На прикладі двох промислових економно леґованих титанових стопів, — мало
леґованого α + β-стопу ti–6Al–4V (мас.%) і метастабільного βстопу ti–1,5Al–
6,8Mo–4,5Fe, — виготовлених одноразовим електроннопроменевим топленням з
проміжною ємністю, вивчено вплив формованої за подальших (термомеханічно
го та термічного) оброблянь мікроструктури на механічну поведінку (виражену
через енергію деформації UD) при випробуваннях з різними швидкостями де
формації та балістичну стійкість. Встановлено, що найменша залежність UD від
швидкости деформації відповідає стопу ti–6Al–4V, відпаленого за температури
двофазної α + β-области, в той час як цей же стоп із пластинчастою мікрострук
турою (піс ля відпалювання в однофазній βобласті), як і стоп ti–1,5Al–6,8Mo–
4,5Fe у різних структурних станах, характеризується інтенсивним пониженням
вели чини UD з ростом швидкости деформації. Окрім того, тільки відпалений за
тем ператури двофазної α + β-области матеріял після випробувань на триточковий
вигин характеризувався тим, що для кожної швидкости деформації величина UD
дорівнювала сумі аналогічних характеристик, одержаних випробуваннями на
розтягання та стискання. При наступних балістичних випробуваннях пластин
цих стопів різної товщини було встановлено, що найліпша балістична стійкість
відповідає матеріялам, які характеризуються великими значеннями UD та мен
шою її чутливістю до швидкости деформації. Детально обговорюється пошко
дження стопів при випробуваннях різних типів з точки зору ймовірних механіз
мів деформації та руйнування.
Ключові слова: титанові стопи, мікроструктура, механічні властивості, механічна
поведінка, швидкості деформації, енергія деформації, балістичні випробування.
О.М. Ивасишин 1, С.В. Ахонин 2, Д.Г. Саввакин 1, В.А. Березос 2,
В.И. Бондарчук 1, А.А. Стасюк 1, П.Е. Марковский 1
1 Институт металлофизики им. Г. В. Курдюмова НАН Украины,
бульв. Академика Вернадского, 36, 03142 Киев, Украина
2 Институт электросварки им. Е. О. Патона НАН Украины,
ул. Казимира Малевича, 11, 03150 Киев, Украина
ВЛИЯНИЕ мИКРОСтРуКтуРы, СпОСОбА И СКОРОСтИ
ДЕфОРмАЦИИ НА мЕхАНИчЕСКОЕ пОВЕДЕНИЕ
СпЛАВОВ Ti−6Al−4V И Ti−1,5Al−6,8Mo−4,5Fe,
пРИгОтОВЛЕННых эЛЕКтРОННО-ЛучЕВОЙ пЛАВКОЙ
На примере двух промышленных экономно легированных титановых спла
вов, — малолегированного α + βсплава Тi–6Al–4V (масс.%) и метастабильного
βсплава ti–1,5Al–6,8Mo–4,5Fe, — приготовленных однократной электроннолу
чевой плавкой с промежуточной ёмкостью, изучено влияние формируемой при
336 ISSN 1608-1021. Prog. Phys. Met., 2018, Vol. 19, No. 3
O.M. Ivasishin, S.V. Akhonin, D.G. Savvakin, V. A. Berezos, V. I. Bondarchuk et al.
последующих (термомеханической и термической) обработках микроструктуры
на механическое поведение (выраженное через энергию деформации UD) при
ис пы таниях с разными скоростями деформации и баллистическую стойкость.
Установлено, что наименьшая зависимость UD от скорости деформации соответ
ствует сплаву ti–6Al–4V с близкой к глобулярной морфологией микрострукту
ры, в то время как этот же сплав с пластинчатой микроструктурой (после от
жига в однофазной βобласти), как и сплав ti–1,5Al–6,8Mo–4,5Fe в различных
структурных состояниях, характеризуется интенсивным снижением величины
UD с ростом скорости деформации. Кроме того, только отожжённый при темпе
ратуре двухфазной α + β-области материал после испытаний на трёхточечный
изгиб характеризовался тем, что для каждой скорости деформации величина UD
была равна сумме аналогичных характеристик, полученных испытаниями на
растяжение и сжатие. При последующих баллистических испытаниях пластин
этих сплавов различной толщины было установлено, что наилучшая баллисти
ческая стойкость соответствует материалам, характеризуемым большими значе
ниями UD и меньшей её чувствительностью к скорости деформации. Подробно
обсуждается повреждение сплавов при испытаниях разных типов с точки зрения
вероятных механизмов деформации и разрушения.
Ключевые слова: титановые сплавы, микроструктура, механические свойства,
механическое поведение, скорости деформации, энергия деформации, баллисти
ческие испытания.
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