The effects of forming pressure and hold-pressure time on the microstructure and mechanical properties of the high strength and toughness Al-5 Mg-2 Si-Mn alloy were investigated by OM and SEM.The results show that with the forming pressure of 100 MPa for 10 s

the average grain size and shape factor of α-Al in the alloy can reach up to 29.59 μm and 0.76 respectively

and the Mg

2

Si phase is mainly dispersed in the form of dots or rods with the obvious inbihition of the precipitation of intermetallic compounds. Meanwhice

the tensile strength and elongation of the alloy is increased from 185 MPa and 3.1% in gravity casting to 312 MPa and 13.5%

increased by 68.6% and 335.5%

respectively.