Martensitic transformation and superelasticity in off-stoichiometric Co2Cr(AlSi) Heusler alloys

Martensitic transformation behaviors and magnetic properties in off-stoichiometric Co2Cr(AlSi) Heusler alloys were investigated mainly by TEM, DSC, SQUID and mechanical test. In Co57Cr21Al11Si11 alloy, martensitic transformation from Heusler-type L21 to D022 phase was confirmed, where Ms and Af temperatures were 429 and 452 K, respectively, suggesting thermoelastic martensitic transformation because of the small transformation temperature hysteresis. In polycrystalline Co57Cr25Al10Si10 alloy with large grains, superelasticity with a recovery strain of over 2% was detected by compression test at 298 K. Thus, a novel Co-based shape memory alloy was discovered in the Co-Cr-Al-Si system.