This study aimed to investigate the change of microstructures and mechanical properties with the solidification rate of AZ91D magnesium alloy. In older to change the solidification rate of AZ91D melt, the pouring temperature and amount of inoculant(C₂Cl_6) were controlled and the permanent mold of cone type was used. The microstructure of as-cast specimens was investigated by optical microscope and scanning electron microscope(EDS) analysis and the grain size was measured by planimetric method. The variations of hardness and tensile properties on the grain size were investigated, and the deformed specimen was observed by TEM. In case the solidification rate was below about 20℃/sec, the grain refinement increases markedly as the solidification rate is increased, but the degree of grain refinement was diminished to higher solidification rate. The Hall-Petch relationship between grain size and hardness, yield strength was held good and the values of 53.0, 419.6 for σ_o and k were obtained, respectively. |
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