한국주조공학회

Improvement of the mechanical properties of a commercial aluminium casting alloy, A356, was achieved through an optimised combination of alloying elements, modification, and heat treatment. 0.7 wt.% Cu and an additional 0.2 wt.% Mg were added to an Al-7Si-0.35Mg alloy for strengthening at both room and elevated temperatures, whilst a subsequent decrease in the ductility was compensated for by the modification of eutectic Si by Sr addition at a level of up to 110 ppm. It was found that the dissolution of Cu-rich or Mg-rich phases could be maximised by solid-solutio solutionising an alloy with 40 ppm Sr at 530oC, increasing the tensile and yield strengt strengths to 350 MPa and 297 MPa, respectively, with a reasonably high strain of 5% after p after peak solutionising an alloy with 40 ppm Sr at 530oC, increasing the tensile and yield strengths to 350 MPa and 297 MPa, respectively, with a reasonably high strain of 5% after peak-aging at 210oC. Further addition of Sr up to 110 ppm is, however, more likely to interfere with the dissolution of the Cu-rich or Mg-rich phases during solid solution treatment, resulting in a slight decrease in both tensile and yield strengths at room temperature. Besides the Cu addition, such undissolved phases, on the other hand, may contribute to elevated temperature strength at 200oC.

Aluminium foundry alloys, Modification, Heat treatment, Microstructure, Mechanical properties