Abstract:Sn was used to replace Al in Co₃₈Ni₃₄Al₂₈ alloy. The microstructure and microhardness of Co₃₈Ni₃₄Al_28-xSn_x (x=0, 1, 2, 3) magnetic shape memory alloys were investigated at different heat treatment temperatures (1373 K, 1473 K, and 1573 K) for 2 h. The results show that more Sn substitution reduces the content of γ-phase and a partial phase of martensite can be obtained in Co₃₈Ni₃₄Al_28-xSn_x (x=1, 2, 3) alloys after treatment at 1573 K for 2 h. The maximum martensite phase appears when 2% Al is substituted by Sn. The reverse martensitic transformation temperature of Co₃₈Ni₃₄Al_28-xSn_x alloys increases at x=1 and 2, then decreases as x=3. As the content of Sn and the temperature increase, the microhardness will increase.

Key words: magnetic shape memory alloy; Sn substitution; Co-Ni-Al alloy; microstructure; mart, ensitic transformation