EBSD analysis of dual γ/ε phase microstructures in tensile-deformed Fe-Mn-Si shape memory alloy

Future Trends on Displacive Stress and Strain Induced Transformations in Steels

“…Regarding α', ε, and αB DIT, they happen below the critical temperatures , and , respectively, provided that the applied stress is higher than a critical stress , , or , respectively, always higher than the austenite , as previously mentioned and shown in Figure 2 [23,25]. Similarly to martensite SIT, from now on, when it is aimed to talk about a critical temperature for martensite DIT and it is not necessary to specify whether the product phase is α' or ε, the general term is used.…”

“…The appearance of the metastable phases named in this section as a product of SIT/DIT mainly depends on the chemical composition of the steel and on the deformation temperature. Hence, whereas the formation of stress or strain induced α is very common in many different microstructures [23,25,35,[49][50][51][52][53][54][55][56], ε is mainly found in austenitic steels [23,25,39,48,52], although it has been sporadically detected in multiphase steels [47]. The formation of α B has not been reported, to the authors' knowledge, at room temperature, although it has been found in fully austenitized steels [35] and in multiphase steels [1,3,57] deformed at high temperatures.…”

“…Regarding variant selection, stress/strain induced α [23,[50][51][52]112], and ε [23,48,52] present this phenomenon. Even when the transformation happens from a fully austenitic structure, there is no agreement about the reasons of the variant selection phenomenon.…”

“…Even when the transformation happens from a fully austenitic structure, there is no agreement about the reasons of the variant selection phenomenon. While some authors claim that variant selection in transformations from a fully austenitic structure may be explained by the mechanical driving force criterion [48,[50][51][52], other authors suggest that some transformation sequences lead to local stress fields which make the analysis more complex [23]. The rules governing variant selection in TRIP transformations in multiphase structures-i.e., formation of stress or strain induced phases from retained austenite-have not been deeply studied.…”

“…However, the optimization of the mechanical properties by TRIP effect is not straightforward. The effect of the stress or strain induced martensite on the mechanical properties can vary depending on several factors, such as the thermal or mechanical austenite stability [23,24] and the product phase [25]. In addition, the complexity of the initial microstructure can also have other effects on these transformations, such as the effect of the matrix in multiphase steels [26][27][28].…”