A Role of α′ Martensite Introduced by Thermo-Mechanical Treatment in Improving Shape Memory Effect of an Fe-Mn-Si-Cr-Ni Alloy

The evolution of alpha' martensite with different thermo-mechanical treatment and its effect on the shape memory effect were studied in an Fe-14Mn-5Si-8Cr-4Ni alloy. The alpha' martensite was introduced by only 5% pre-deformation, and its amount increased with increasing pre-deformation up to 20%. The alpha' martensite started to transform into austenite when the annealing temperature was 773 K. As the annealing temperature increased to 1 073 K, the alpha' martensite almost transformed fully into austenite. The alpha' martensite introduced by the thermo-mechanical treatment could prevent collisions between different e martensite bands during deformation. The intrusion of alpha' martensite was another key reason that the stress-induced e martensite bands in Fe-Mn-Si based shape memory alloys formed in a domain-specific manner in addition to that of uniformly distributed stacking faults after thermomechanical treatment.