Deformation Behaviour and Successive-and-"Continuous" Transformation in the Cu-Al Alloys During Tensile Deformation

Abstract

Deformation behaviour and the structure of the M phases of the single crystal of the Cu-12mass%Al and Cu-13.4mass% alloy were investigated by tensile deformation and EM observation. In the present work it was found that the direct transition from 18R to 3R or 2H to 3R does not take place but transition undergoes passing through a new long period(L.P.) intermediate M phase (from 10 to 45 stacking) and reaches the final 3R(DO 22 ) M phase. During L.P.to 3R transition a typical pseudoelastic behaviour was observed during loading-unloading cycle and the width of the hysteresis loop between loading and unloading varied with testing temperature and the tensile cycling. The width of the loop decreses with increasing testing temperature and also with increasing testing cycle in both the alloys. These facts suggest that in the Cu-Al alloys a kind of continuous M to M transformation exhibits during cyclic tensile deformation in addition to the ordinary successive 18R or 2H to 3R transformation.