To enhance the mechanical properties of cast Al–Si–Cu alloys (ADC12), 0.3% of carbon nanotubes (CNTs) was added. The cast ADC12–0.3%CNT samples were synthesised via heated mould continuous casting for the creation of fine grains, and the artificial aging process was conducted at 173°C for 13 h to obtain precipitation hardening. The reinforcement and refinement of eutectic Si and precipitates (Al2Cu and Mg2Si) were achieved by adding CNTs, which leads to a high tensile strength of about 450 MPa and a relatively high ductility of about 10%. The obtained tensile strength and 0.2% proof stress are more than twice as high as those of the conventional cast ADC12 alloy. The refinement of the microstructures could be due to the interruption of their growth caused by the CNTs.

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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 Mg 97 Y 2 Zn 1 -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 (Al 84.7 Si 10.5 Cu 2.5 Fe 1.3 Zn 1 alloys: ADC12), made by the GC process. Moreover, the tensile properties ( UTS and  f ) and fatigue properties of the Mg 97 Y 2 Zn 1 -HMC alloy were about 1.5 times higher than that for the commercial Mg 90 Al 9 Zn 1 -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 Mg 97 Y 2 Zn 1 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.