Abstrakt
In this paper, the possible superplastic behaviour of fine-grained magnesium alloys AE42 and LAE442 alloys was investigated and the first results of this research are shown. Two deformation temperatures and two strain rates were selected upon the initial measurement of thermal stability and dependence of m-parameter on strain rate and temperature.
Evolution of m-parameter during the tensile tests was measured by means of periodical switching of the strain rate. The LAE442 alloy showed significantly higher elongations at the same deformation conditions as comparing to the AE42 alloy.
The highest values of m-parameter in the last stage of deformation were measured at the temperature of 240 degrees C and strain rate of 10(-4) s(-1), regardless much higher grain growth comparing to deformation at 180 degrees C. Consequently, deformation of about 1.5 (350 %) and 1.3 (270 %) was measured for LAE442 and AE42 alloys, respectively.
Higher values of m-parameter during the deformation and consequently higher elongation observed in LAE442 alloy were attributed to a combination of higher thermal stability and the positive effect of lithium on the activation of non-basal slip systems and diffusion.