Effects of alloying elements Mg

Cu and heat treatment on microstructure and mechanical properties of AlSiMgMn alloys fabricated by squeeze casting were investigated by OM

SEM and EDS.For the AlSiMgMn alloys with trace Sr modification

the eutectic silicon modification levels are about grade 5 according to the American Foundry Society（AFS）standard chart for Al-Si alloys.The AlSiMgMn alloys with 0.3% Mg or 0.5% Mg show the same optimized heat treatment parameters:solution at 535 ℃for 4 and aging at 160 ℃ for 6.While the Mg content in AlSiMgMn alloys is increased from 0.3%to 0.5%

the tensile strength and yield strength of the alloy prepared are increased by 60 MPa and 70 MPa

respectively.Replaced Sr with Sb for modification of the AlSiMgMn alloy with 2.5%Cu addition

in consideration of the detrimental effect of Cu on Sr modification

the modification level of eutectic silicon is about grade 3

4

.Although eutectic silicon particles could be spheroidized well in the subsequent heat treatment

the particle aggregation occurs obviously because of non-uniform modification effect in the casting process.It is found that strength of squeeze cast AlSiMgMn alloy is improved obviously by Cu addition

where tensile strength

yield strength and elongation of the alloy after T6 treatment reach 435 MPa

338 MPa and 7.0%

respectively.