Interaction of high-temperature deformation mechanisms
High-temperature tensile tests have been conducted on a magnesium alloy (Mg-1.5 pct Mn-0.3 pct Ce) with randomly mixed fine and coarse grains. The microstructural examinations clearly show that different mechanisms operate in the regions of coarse and fine grains. The coarse grains deform by dislocation slip, while grain boundary sliding occurs in the fine grains. The influence of these mechanisms on each other has also been observed in terms of dislocation density, intragranular slip lines, and grain boundary sliding. The analytical equations describing the interaction of two deformation mechanisms operative in materials with regions of fine and coarse grains were derived. The analysis is applicable for determining the controlling mechanism of two interacting mechanisms. It is predicted that at a critical volume fraction of fine grains of approximately 40 pct, a transition from superplastic to nonsuperplastic behavior occurs.
KeywordsMetallurgical Transaction Magnesium Alloy Deformation Mechanism Dislocation Slip Transmission Electron Microscope Photograph
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