Cooperative Effects between γ′₁ and β′₁ Martensites in a Cu-15.0 at%Sn Alloy

Abstract

Electron microscopy observations have been carried out to study some characteristics of martensites formed in a Cu-15.0 at%Sn alloy which was subzero treated. It was found that an 18R-martensite (β′₁) is formed at the interface between the 2H-martensite (γ′₁) and the parent phase (β₁). The volume of the 18R-martensite increases upon heating. The β′₁ martensite appears to form as a result of stress-assistment from the γ′₁ martensite. The coexistence of the two martensites is believed to be a major cause of the sensitive dependence of the A_s and A_f temperatures upon the heating rate in this alloy.