Microstructures and room temperature mechanical properties of Al-6.3Zn-2.8Mg-1.8Cu casting aluminum alloy

The microstructures and room temperature mechanical properties of metal-mold-casting aluminum alloy Al-6.3Zn-2.8Mg-1.8Cu were studied. It was found that the microstructure of the as-cast experimental alloy consists of near equiaxed α(Al) matrix, α(Al)+η(MgZn ₂) eutectic and little Al ₇Cu ₂Fe particle phase. The phase constitution of the quenched experimental alloy was changed, the η phase was dissolved into α(Al) matrix and tended to disappear, however a new phase, S(Al ₂CuMg), appeared, which still mainly distributed along the α(Al) grain boundary. The optimum single-aging process parameters were determined by investigating age hardening response of the experimental alloy. It was found that the double-aging process could make the tensile strength of the experimental alloy increase from 480 MPa to 490 MPa, and the elongation from 0.2% to 2.2%, comparing with the single-aging process.