Effect of ECAP on the Microstructure and Mechanical Properties of a High-Mg2Si Content Al-Mg-Si Alloy

A high-Mg2Si content Al alloy was extruded by equal channel angular pressing (ECAP) for 8 passes at 250 degrees C and an ultrafine-grained structure with an average grain size of about 1.5 mu m was achieved. The coarse skeleton-shaped Mg2Si phase presenting in the as-cast alloy are significantly fragmented into fine rod-shaped as well as equiaxed particles mostly less than about 230 nm and become relatively dispersed. The tensile strength 192.8 MPa and the elongation up to 31.3% at ambient temperature are attained in the 8-pass ECAPed alloy versus 163.3 MPa and 9.1% in the as-cast alloy. High-temperature creep test at 250 degrees C reveals that the ECAPed sample exhibits a high elongation close to 100% at a relatively high creep rate 7.64x10(-5) s(-1), compared to the elongation 56% at a low strain rate 1.74x10(-7) s(-1) in the as-cast alloy. Key words: equal channel angular pressing (ECAP); deformation and fracture; metals and alloys.