INTERPRETATION OF CONSTANT-LOAD AND CONSTANT-STRESS CREEP-BEHAVIOR OFA MAGNESIUM ALLOY PRODUCED BY RAPID SOLIDIFICATION

The creep behaviour of an Mg-Zn-Ca-Ce-La alloy produced by rapid solid ification was investigated by means of constant-load creep tests carri ed out at 498, 523 and 548 K. The analysis of strain rate as a functio n of applied stress suggests that in the ranges of stress and temperat ure studied, the creep mechanism is glide on basal plane controlled by cross-slip on non-basal planes or dislocation glide limited by the nu cleation of kinks. This behaviour contrasts with previous results obta ined in pure Mg where cross-slip on non-basal planes was the rate-cont rolling mechanism only at higher temperatures. The different behaviour of this alloy is attributed to the very tine grain size typical of ra pidly solidified material. The enhancement in strain rate observed in the present alloy can be attributed to grain-boundary sliding accommod ating the strain produced by dislocation creep mechanism; (glide on no n-basal plane controlled by cross-slip or dislocation glide limited by the nucleation of I;inks) that operate in the subgrain interior. (C) 1998 Elsevier Science S.A. All rights reserved.