Creep behaviour of Cu-30% Zn at intermediate temaperatures

Abstract

The creep properties of single-phase Cu-30% Zn alpha brass were investigated in the intermediate temperature range 573–823 K (0.48–0.70T _m, whereT _m is the absolute melting point). Inverse, linear, and sigmoidal primary creep transients were usually observed above 573 K under stresses resulting in minimum creep rates between 10⁻⁷ and 2×10⁻⁴s⁻¹, while normal primary creep occurred under all other conditions. The creep stress exponent decreased from about 5.4 at 573 K to about 4.1 above 623 K, and the activation energy for creep varied between 170 and 180 kJ mol⁻¹. A detailed analysis of the data, as well as a review of the literature, suggests that no clearly defined class M to class A to class M transition exists in this alloy, although the characteristics of both class A and class M behaviour are observed under nominally similar stresses and temperatures. It is concluded that Cu-30% Zn does not conform to the normally accepted characterization of class A or class M solid solution alloys.