Deformation behavior of FCC multicomponent alloys of different stacking fault energies at close to 0K (12/12/23)

Speaker and Affliation:

Dr. Aditya Srinivasan Tirunilai
Research Associate
Chair for Materials Science and Engineering (MSE)
Ruhr University Bochum (RUB) Universitätsstr. 150, 44780 Bochum, Germany


12th December, 2023 (Tuesday), 3.00 PM (India Standard Time)


K I Vasu Auditorium, Dept. of Materials Engineering, IISc, Bangalore


The deformation behavior of multicomponent alloys, both single and multiphase, has recently been a point of keen interest. Single-phase FCC alloys have especially attracted significant scientific attention, with several alloys from the Cantor (Cr-Mn-Fe-Co-Ni) system exhibiting excellent mechanical properties at room temperature and 77 K. Based on these results, predictions were made about the cryogenic behavior of equiatomic CrCoNi and CrMnFeCoNi. These predictions are evaluated through deformation experiments carried out at 4 K. The active deformation mechanisms are identified using SEM and TEM and correlated with work-hardening rate variations. The differences between the reportedly low stacking fault energy (SFE) CrCoNi and medium SFE CrMnFeCoNi are illustrated, with multiple assertions/predictions being refuted, including expectations of martensite formation and contribution to strengthening. Contrastingly a non-equiatomic, expectedly high SFE, multicomponent alloy (Fe40Ni11Mn35Al8Cr6)C1 was chosen to evaluate deformation behavior in the same temperature range. This alloy was not expected to exhibit deformation twinning or martensite formation, unlike the previous two alloys, but microband-induced plasticity. Surprisingly, it exhibits deformation twinning as well as microband formation at cryogenic temperatures. This conflicting combination is reconciled as a result of solid solution strengthening and its effect as a function of temperature. The effect of solid solution strengthening in this case far surpasses even that in CrMnFeCoNi.