Investigation of the tensile and fatigue properties of cast magnesium alloys, created by the heated mold continuous casting process (HMC), was conducted. The mechanical properties of the Mg-HMC alloys were overall higher than those for the Mg alloys, made by the conventional gravity casting process (GC), and especially excellent mechanical properties were obtained for the Mg97Y2Zn1 -HMC alloy. This was because of the fine-grained structure composed of the -Mg phases with the interdendritic LPSO phase. Such mechanical properties were similar levels to those for conventional cast aluminum alloy (Al84.7Si10.5Cu2.5Fe1.3Zn1 alloys: ADC12), made by the GC process. Moreover, the tensile properties (UTS and f ) and fatigue properties of the Mg97Y2Zn1 -HMC alloy were about 1.5 times higher than that for the commercial Mg90Al9Zn1 -GC alloy (AZ91). The high correlation rate between tensile properties and fatigue strength (endurance limit: l ) was obtained. With newly proposed etching technique, the residual stress in the Mg97Y2Zn1 alloy could be revealed, and it appeared that the high internal stress was severely accumulated in and around the long-period stacking-order phases (LPSO). This was made during the solidification process due to the different shrinkage rate between α-Mg and LPSO. In this etching technique, microcracks were observed on the sample surface, and amount of micro-cracks (density) could be a parameter to determine the severity of the internal stress, i.e., a large amount to micro-cracks is caused by the high internal stress.
The exudation layer seriously affects the properties and the surface finish of the tin bronze alloy. The effective control of the exudation thickness is important measure for improving the properties of the alloy. In order to study the influence of process parameters on the thickness of exudate layer, the tin bronze alloy was prepared by continuous unidirectional solidification technology at different process parameters. The microstructure of the continuous unidirectional solidification tin bronze alloy was analyzed. The effect of process parameters on microstructure and chemical compositions was studied by orthogonal experiment. The results show that there exists an exudation layer on the surface of the continuous unidirectional solidification tin bronze alloy, and the exudation is mainly composed of a tin-rich precipitated phase. It indicates that the continuous casting speed is the main factor affecting the thickness of exudation layer, followed by mold temperature, melt temperature, cooling water temperature and cooling distance.