挤压铸造工艺对Al-7Si-0.4Mg-0.3Er汽车左支架组织与性能的影响

The effect of squeeze casting process on the microstructure and properties of Al-7Si-0.4Mg-0.3Er alloy bracket was investigated by OM, SEM and microhardness test. The results show that the solidification sequence has great influence on the microstructure of different parts of the bracket. The size of primary α-Al grains in the first solidified thin-wall is smaller than that in the later solidified thick-wall. The primary α-Al phase in the bracket fabricated by low pouring temperature is smaller and more uniformly distributed than that fabricated by high pouring temperature, but the Er-π-AlFeMgSi phase in the bracket fabricated by low pouring temperature is coarse and partially distributed. The Er-π-AlFeMgSi phase in the bracket fabricated by high speed is smaller and more uniformly distributed than that fabricated by low speed. The microhardness (HV) and standard deviation of the bracket fabricated by low pouring temperature (650℃) and high speed are 1190 and 50 MPa after heat treatment, respectively. The properties are more uniformly distributed than those of the bracket fabricated by low temperature and low speed. Al-Si alloy engine bracket is suitable for forming at low pouring temperature and high extrusion speed.