Dispersoid characteristics and elevated temperature creep resistance of Al–Si–Mg cast alloy with Zr addition

The present work aims to reveal the dispersoids evolution and the valuable role of Zr on the elevated-temperature creep resistance of Al–7Si-0.3Mg alloy. At 300°C and 25 MPa, Al–7Si-0.3Mg-0.15Zr alloy exhibits more than double decrement in the minimum creep rate, and 263 h increment in creep time-to-fracture compared to the Zr-free cast alloy. These effects were owe to the formation of novel nanobelt-like Si2Zr and rectangle-like (Al, Si)3–Zr dispersoids during solutionising at 560°C for 20 h. The Si atoms could substitute for Al sites to form stable L12-Al2Si1Zr structure. The thermally stable dispersoids were semi-coherent/coherent with the Al matrix, which impeded the movement of dislocations during creep deformation at 300°C. It demonstrated that the superior creep resistance (300°C) achieved in the Al–7Si-0.3Mg-0.16Zr alloy was attributed to the introduction of novel Zr-containing dispersoids.