The Effect of Heat Treatment on the Martensitic Transformation and Properties of Cu-Zn-Al Alloy

Abstract

The effects of various quenching treatments including direct quenching, up-quenching, step-quenching in boiling water and step-quenching in an oil bath were studied on a Cu-20.8Zn-5.8Al (mass%) shape memory alloy. The aging behaviors of variously quenched specimens have also been investigated. The thermally recoverable martensitic deformation in quenched specimens was determined to be up to 3.2%. The yield stress and transformation temperatures were decreased during aging compared to quenched specimens. In addition, aging resulted in a degradation and ultimate loss of the shape memory capacity. The apparent activation energies of the alloy obtained from loss of shape memory and decrease in the transformation temperatures were ranged from 64 to 74 kJmol· 1. The life expectancy predictions indicate that devices made from the alloy will lose their shape memory capability after exposure at 373 Κ for time ranged from 52 to 60 days. However, relatively long memory life is expected at temperatures below 323 K.