Martensitic transformation and magnetic transition of Ni₅₂Ga₂₈Fe_20-xCo_x alloy

The effects of Co content x on the martensitic and magnetic transition of Ni₅₂Ga₂₈Fe_20-xCo_x alloys were investigated by optical micrography, SEM, DSC and VSM methods. The structure type of martensitic phase was determined by powder X-ray diffraction (XRD). Martensitic tranformation temperatures of Ni₅₂Ga₂₈Fe_20-xCo_x alloys could be elevated quickly by the substitute of Co for Fe element in the Co content range of x≤6, whereas their curie points are unchanged. x value increased by 1 can increase the martensitic transformation temperature by 50-60 K. Annealing at 773 K for 1 h doesn't change the martensitic transformation temperatures-of studied alloys but increases their Curie points by 20-30 K. XRD patterns showed that only L1₀ (2 M) type of martensitic phases appeared in powder samples both annealed at 1423 K and at 773 K.