TY - JOUR

T1 - Diffusive and displacive phase transitions in Ti–Fe and Ti–Co alloys under high pressure torsion

AU - Straumal, B. B.

AU - Kilmametov, A. R.

AU - Ivanisenko, Yu

AU - Mazilkin, A. A.

AU - Valiev, R. Z.

AU - Afonikova, N. S.

AU - Gornakova, A. S.

AU - Hahn, H.

PY - 2018/2/25

Y1 - 2018/2/25

N2 - The high pressure torsion (HPT) of Ti–4 wt. % Fe and Ti–4 wt. % Co alloys has been studied. Before HPT, the samples were annealed above and below the temperature of eutectoid transformation. After quenching, the first samples contained a mixture of α and β phases. The latter samples contained a mixture of α-Ti saturated with Fe or Co and respective intermetallic phases TiFe. During HPT the high-pressure ω-phase formed in all samples. The amount of ω-phase was higher when the initial samples contained the α+β mixture then in the case of α+TiFe or α+Ti2Co mixture. Most probably, the martensitic β→ω transformation occurs easier than the α→ω one. The amount of ω-phase was higher in Ti–Fe alloy than in the Ti–Co alloy for both initial states. It seems that cobalt additions disadvantageously change the lattice parameters in Ti for martensitic β→ω and α→ω transformations. The phase transformations with mass transfer (diffusive ones) also take place by HPT of Ti–Fe and Ti–Co alloys. Both α-based solid solutions partially decomposed after HPT. After HPT, the lattice parameters of α-phase containing cobalt or iron changed towards those of pure α-Ti. It has been observed for the first time that the composition of TiFe phase also changes after HPT.

AB - The high pressure torsion (HPT) of Ti–4 wt. % Fe and Ti–4 wt. % Co alloys has been studied. Before HPT, the samples were annealed above and below the temperature of eutectoid transformation. After quenching, the first samples contained a mixture of α and β phases. The latter samples contained a mixture of α-Ti saturated with Fe or Co and respective intermetallic phases TiFe. During HPT the high-pressure ω-phase formed in all samples. The amount of ω-phase was higher when the initial samples contained the α+β mixture then in the case of α+TiFe or α+Ti2Co mixture. Most probably, the martensitic β→ω transformation occurs easier than the α→ω one. The amount of ω-phase was higher in Ti–Fe alloy than in the Ti–Co alloy for both initial states. It seems that cobalt additions disadvantageously change the lattice parameters in Ti for martensitic β→ω and α→ω transformations. The phase transformations with mass transfer (diffusive ones) also take place by HPT of Ti–Fe and Ti–Co alloys. Both α-based solid solutions partially decomposed after HPT. After HPT, the lattice parameters of α-phase containing cobalt or iron changed towards those of pure α-Ti. It has been observed for the first time that the composition of TiFe phase also changes after HPT.

KW - Decomposition of solid solution

KW - High-pressure torsion

KW - Phase transitions

KW - Ti–Co alloys

KW - Ti–Fe alloys

KW - NANOCRYSTALLINE STRUCTURE

KW - B ALLOY

KW - NANOSTRUCTURE

KW - Ti-Fe alloys

KW - PRECIPITATION

KW - SEVERE PLASTIC-DEFORMATION

KW - ZN

KW - Ti-Co alloys

KW - AL-MG ALLOYS

KW - AG ALLOYS

KW - MAGNETIC-PROPERTIES

KW - TRANSFORMATIONS

UR - http://www.scopus.com/inward/record.url?scp=85036639198&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2017.11.317

DO - 10.1016/j.jallcom.2017.11.317

M3 - Article

AN - SCOPUS:85036639198

VL - 735

SP - 2281

EP - 2286

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

ER -