Effect of casting process and Zr, V addition on microstructure and mechanical properties of Al-12Si-4.5Cu-2Ni alloy

The casting process, the type and content of microalloying elements have a significant effect on the microstructure and mechanical properties of Al-12Si-4.5Cu-2Ni alloy. The results showed that with the increase of Zr and V, the grain size and secondary dendrite arm spacing (SDAS) of the alloy decreased. However, excessive Zr and V led to abnormal growth of the intermetallic phase, resulting in the separation phenomenon of the matrix. Compared with gravity casting, squeeze casting not only inhibited the segregation of alloying elements but also refined the size of the intermetallic phase. The mechanical properties of the alloy showed a trend of increasing first and then decreasing. When the content of Zr and V was 0.2, the Al-12Si-4.5Cu-2Ni alloy obtained the best mechanical properties. The ultimate tensile strength, yield strength and elongation were 261.4 MPa, 150.2 MPa and 1.93 %, respectively. The (AlSi)3(ZrV), stacking faults and dislocations in the alloy significantly improved the mechanical properties. The disappearance of pores and the refinement of microstructure elevated the elongation of the alloy, while the dotted intermetallic phase accelerated the initiation of microcracks, leading to a decrease in elongation.