| Abstract: | Study was made of the superplastic deformation mechanism for two selected Mg alloys of either coarse or superfine grain by means of an advanced testing technique. It was shown that the mechanism under superplastic deformation for these two alloys is mainly due to the grain boundary sliding together with the coordination of diffusion creep and dislocation slip. A complex deformation mechanism model including the above mentioned three ones is believed to be proposed. The metal grains may progressively emerge from underneath up to surface during superplastic deformation through grain boundary sliding in the site on which the broadening and cavities along transverse grain boundaries appeared, thus, the number of grains along the tensile axis may be continuously incressed. This seems to be the origin of the extreme elongation of the specimen under tensile deformation. |
