Effect of Co addition on deformation-induced martensitic transformation in Cu-Zr alloy

Thermal stability, phase transformation after deformation and mechanical properties of B2 phase alloy with the compositions of Cu_50-xCo_xZr₅₀ (x = 2, 4, 6, 10, 15, 20, 25, 30, 40, 45 and 50) have been investigated in the present study. The addition of Co in Cu₅₀Zr₅₀ alloy effectively improves the stability of B2 phase. The Ms and As temperatures generally decrease with increasing Co content. Before deformation, the alloys with x = 10, 15, 20, 25, 30, 40, 45 and 50 consist of B2 phase. After deformation, B2-B19' martensitic transition occurs in x = 10, 15, 20 and 25 alloys, and B2-B33 martensitic transition occurs in x = 50 alloys. No martensitic transformation occurs in x = 40 and 45 alloys. The alloys with x = 10, 15, 20 and 25 exhibit double yielding phenomenon and higher strain-hardening rate, owing to B2-B19' martensitic transformation during deformation. The alloys with x = 30, 40, 45 and 50 exhibit lower strain-hardening rate, in spite of conventional dislocation slip or B2-B33 martensitic transformation.