Preparation of semi-solid AZ91D billets by new SIMA method

By using equal channel angular extrusion and semi-solid isothermal treatment, metalloscope and SEM, the microstructure evolution of AZ91D Mg alloy extruded by ECAE was described during semi-solid isothermal treatment. Based on the results, new SIMA method is put forward to prepare AZ91D semi-solid billet. The microstructure of semi-solid billets prepared by new SIMA method is very homogeneous, fine and globular grain with the grain size in the range of 20-50 μm occurs. With increasing holding time, growing phenomenon occurs in the microstructure of the semi-solid billets, which can be described by Ostwald opening law. With the increase of isothermal treatment temperature, grain size is firstly increased then decreased, and its shape factor approached to one. With increasing in equivalent strain obtained by ECAE, grain size is decreased.