PSEUDOELASTICITY IN A Au-47.5at%Cd ALLOY SINGLE CRYSTAL

Abstract
Deformation behavior and its mechanism in a Au-41.5at%Cd alloy single crystal have been investigated at temperatures above and below Ms, by tensile and compressive tests, optical microscopy, X-ray diffraction and two-surface trace analysis. In a temperature range above Ms, two types of martensites are stress-induced depending upon the test temperature ; 2H type at temperatures very near to Ms and 9R type at temperatures somewhat higher than Ms. The formation and reversion of the latter martensite have been shown to be the origin of the transformation pseudoelasticity in this alloy system. In a temperature range below Mf, two types of pseudoelastic behavior, which are unsymmetric in tensile and compressive tests, are observed in a single variant γ₂' martensite, which is produced by cooling a β₂' martensite stress-induced from the β₂ matrix at a temperature above Ms under stress and then by unloading it. That is, pseudoelasticity due to the γ₂' ↔ β ₂' transformations is observed in tensile test, and the one due to movement of twin boundaries in the γ₂' martensite in compressive test.