Effect of ageing and thermal exposure on microstructure and mechanical properties of a HPDC Al-Si-Cu-Mg alloy

Mechanical behavior and microstructure evolution of a newly developed high strength die casting Al-13Si0.25Cu alloy (in wt%) were investigated under as-cast, peak-aged and thermal-exposed conditions. In the as-cast condition, the alloy has a yield strength (YS) of 213 MPa and an elongation (El) of 4.6%. The alloy YS is further improved to 265 MPa after T5 ageing treatment. The enhancement of YS after ageing is attributed to the precipitation of nanoscale beta '', Q' and theta' phase from the alpha-Al matrix. After thermal exposure at 350 degrees C for 100 h, however, these precipitates mostly dissolve into the alpha-Al matrix and the ultrafine eutectic Si networks undergo breaking and coarsening, reducing YS to 117 MPa while enhancing the El to 10.3%.

Automated summary

The mechanical behavior and microstructure evolution of a newly developed high strength die casting Al-13Si0.25Cu alloy were investigated in different conditions, showing that ageing treatment can improve the yield strength while thermal exposure can result in reduced hardness and increased ductility.