EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

High-entropy alloys (HEAs) constitute a new class of metallic materials attracting increased attention due to unusual combination of mechanical and functional characteristics. One of a strategy to design Ti-rich high entropy alloys with various active modes of deformation mechanisms (such as TRIP, TWIP or dislocation slip) is using the bond order (Bo) - mean d-orbital energy level (Md) approach. The primary objective of the present study is to investigate deformation mechanisms of new Ti-rich bcc HEAs designed using the Bo–Md approach. Three alloys of Ti-Zr-Hf-Ta-Sn, Ti-Zr-Nb-Al-V and Ti-Zr-Nb-Al-Mo systems were considered. The studied alloys demonstrated very unusual combinations of mechanical properties depending on the operating deformation mechanisms. Specifically the Ti38Zr25Hf25Ta10Sn2 alloys demonstrated exceptionally high strain - hardening and ductility due to deformation-induced martensite transformation. The Al5Nb24Ti40V5Zr26 and Al4Mo4Nb8Ti50Zr34 high-entropy alloys in recrystallized conditions showed properties typical of gum like metals, i.e. high strength, low work hardening and rather large elongation. The manifestation of such behavior can be ascribed to the formation of dislocation channels due to the local disordering of the bcc matrix in shear planes.
It was suggested, based on the obtained result, that the ‘d-electron alloy design’ approach can be used to predict not only TRIP/TWIP effect in Ti-rich alloys, but also some other effect of plastic flow localization caused by low stability of the bcc lattice, including the formation of deformation bands or giant faults in gum like metals.