INFLUENCE OF Sb ADDITION ON MARTENSITIC AND MAGNETIC TRANSFORMATIONS OF (β+γ) TWO-PHASE Co-Ni-Al SHAPE MEMORY ALLOY
Influence of Sb addition on Martensitic and Magnetic Transformation in β+γ Two-phase Based Co-Ni-Al Shape Memory Alloy

Influence of 1% Sb(atomic fraction)addition in the Co_(41)Ni_(32)Al_(27) alloy on martensitic transformation and Curie temperature of the alloy was investigated by OM,SEM,EDX,XRD,DSC and VSM methods.The results show that the crystal structure of martensitic in Co_(41)Ni_(32)Al_(26)Sb_1 alloy is Llo type,as the same as the Co_(41)Ni_(32)Al_(27).Both martensitic transformation temperature T_m and Curie temperature T_C are linear relation to quenching temperature.T_m increased 9 K and T_C increased 7.5 K for every 10 K increasing in quenching temperature.Quenched from same temperature,T_m of Co_(41)Ni_(32)Al_(26)Sb_1 alloy is higher than that of Co_(41)Ni_(32)Al_(27)alloy by 70 K,meanwhile T_C is higher by 15 K.The melting temperature of Co-Ni-Al alloy decreased by the addition of Sb,eutectic structure appeared in Co_(41)Ni_(32)Al_(26)Sb_1 alloy quenched at 1623 K,indicating that the alloy was partially melted. The martensitic transformation temperature range of Co_(41)Ni_(32)Al_(26)Sb_1 alloy is 20-28 K,less than half that of Co_(41)Ni_(32)Al_(27) alloy.This is a very important result to benefit the achievement of large magnetic field induced strain on Co-Ni-Al based alloy.The results of T_m and T_C were explained by total average s+d electron concentration and magnetic valence number,Z_m separately.