TY - JOUR

T1 - Modelling martensitic transformation in titanium alloys

T2 - The influence of temperature and deformation

AU - Bignon, Madeleine

AU - Bertrand, Emmanuel

AU - Tancret, Franck

AU - Rivera-Díaz-del-Castillo, Pedro E. J.

PY - 2019/9/1

Y1 - 2019/9/1

N2 - New theory is presented to describe the occurrence of plasticity-induced transitions in titanium alloys. The approach is able to predict the composition dependence of transformation induced plasticity (TRIP), superelasticity, as well as martensite formation upon quenching. Martensite formation in the absence of stress is considered as the result of a competition between elastic strain energy and chemical driving force. Assuming that the formation of martensite is the result of a thermally activated nucleation process followed by athermal growth, a nucleation parameter is postulated to describe the conditions under which martensite is formed upon quenching; the parameter accounts for the ratio between the available thermal energy and an energy barrier for nucleation, suggesting that ω phase is not the main factor controlling martensite inhibition. This nucleation parameter is able to describe, for the first time, martensite occurrence in 130 alloys from the literature, quantifying the martensite start temperature (Ms) reported for 49 alloys with great precision. An empirical parameter ([Fe]eq) is proposed and, when combined with the Ms prediction, it allows to define regions within which TRIP and superelasticity occur. By defining threshold values for the Ms, the [Fe]eq and the nucleation parameter, candidate alloys likely to display TRIP, superelasticity or martensitic transformation upon quenching can be identified. As a result, this method can be adopted to design alloys with tailored plasticity behaviour. © 2019 Acta Materialia Inc.

AB - New theory is presented to describe the occurrence of plasticity-induced transitions in titanium alloys. The approach is able to predict the composition dependence of transformation induced plasticity (TRIP), superelasticity, as well as martensite formation upon quenching. Martensite formation in the absence of stress is considered as the result of a competition between elastic strain energy and chemical driving force. Assuming that the formation of martensite is the result of a thermally activated nucleation process followed by athermal growth, a nucleation parameter is postulated to describe the conditions under which martensite is formed upon quenching; the parameter accounts for the ratio between the available thermal energy and an energy barrier for nucleation, suggesting that ω phase is not the main factor controlling martensite inhibition. This nucleation parameter is able to describe, for the first time, martensite occurrence in 130 alloys from the literature, quantifying the martensite start temperature (Ms) reported for 49 alloys with great precision. An empirical parameter ([Fe]eq) is proposed and, when combined with the Ms prediction, it allows to define regions within which TRIP and superelasticity occur. By defining threshold values for the Ms, the [Fe]eq and the nucleation parameter, candidate alloys likely to display TRIP, superelasticity or martensitic transformation upon quenching can be identified. As a result, this method can be adopted to design alloys with tailored plasticity behaviour. © 2019 Acta Materialia Inc.

KW - Martensite

KW - Superelasticity

KW - Titanium alloys

KW - TRIP

U2 - 10.1016/j.mtla.2019.100382

DO - 10.1016/j.mtla.2019.100382

M3 - Journal article

VL - 7

JO - Acta Materialia

JF - Acta Materialia

SN - 2589-1529

M1 - 100382

ER -