Creep behaviour at high stresses of a Mg-Zn-Ca-Ce-La alloy processed by rapid solidification

Abstract

In the present paper it was shown that under the above conditions of temperature and applied stress given, the creep strain rate is controlled by the matrix lattice diffusion and is not associated with a threshold stress. The true stress exponent n of the creep strain rate was found close to 7. These findings were compared to those obtained [1] for the same temperature interval and applied stresses lower than about 85 MPa. Under these "lower stress" conditions the creep is dislocation glide controlled (Peierls or quasi-Peierls mechanism) and is associated with temperature dependent threshold stress. The true stress exponent n is much lower than that for the "higher stress" region and decreases with increasing temperature. The differences in the creep behaviour of the Mg-alloy B in the high stress region and low stress region are discussed. The absence of threshold stress in the high stress region has not been accounted for finally. Some important creep characteristics (ΔHc, n, σTH) are summarized in the form of a "diagram of creep" of the alloy. Also, the creep behaviour of the alloy investigated is compared with that of pure magnesium.