Corrosion Behaviors of Permanent Mold Cast Mg Alloy AJ62 with Varying Grain Structures in Automotive-Related Environments

Permanent mold cast (PMC) AJ62 magnesium alloy exhibits a fine-grained microstructure in the thin section and a coarse-grained microstructure in the thick section. Microstructure of the PMC AJ 62 alloy was analyzed by using the Scanning Electron Microscopy (SEM). Potentiodynamic polarization experiments were performed to investigate the corrosion resistances of the PMC AJ62 alloys in salt solutions and engine coolant. The corrosion behaviors in the fine- and coarse-grained AJ62 alloys were compared. The results show that the AJ62 alloy with fine microstructure presents enhanced corrosion resistance.

Low-Cycle Fatigue Behavior of Permanent-Mold Cast and Die-Cast Al-Si-Cu-Mg-Sc Aluminum Alloys

The low-cycle fatigue behaviors of permanent-mold cast and die-cast Al-Si-Cu-Mg-Sc alloys at room temperature were investigated. The results show that at the higher total strain amplitudes, both permanent-mould cast and die-cast Al-Si-Cu-Mg-Sc alloys exhibit the cyclic strain hardening. However, at the lowest total strain amplitude, the cyclic strain hardening occurs in the initial and middle stages of fatigue deformation and the stable cyclic stress response is noted in the later stage of fatigue deformation for the permanent-mould cast alloy, while the cyclic strain hardening phenomenon is observed during whole fatigue deformation for the die-cast alloy. At the same total strain amplitude, the die-cast alloy shows the higher cyclic deformation resistance than the permanent-mold cast alloy. Compared with the permanent-mold cast alloy, the die-cast alloy possesses the longer fatigue life at the lower total strain amplitudes. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior for both permanent-mold cast and die-cast Al-Si-Cu-Mg-Sc alloys

Microstructure and Aging Behavior of AZ91 Mg Alloy Fabricated by Inclined Cooling Plate

Semi-solid AZ91 magnesium alloys were produced using a cooling plate followed by quenching in the mold. The cast and T6 heat treated microstructures were microscopically characterized and subjected to hardness tests. It was found that the resultant microstructure in water quenched semi-solid specimen were finer than that in conventional permanent mold cast specimen. The hardness tests also showed that the hardness of quenched semi-solid cast specimen was higher than that of permanent mold cast specimen. This was attributed to large amount of precipitates which results from fine precipitation of eutectic phase at intergranular areas during the aging treatment after its complete dissolution.