Using equal channel angular extrusion and semi-solid isothermal treatment

metalloscope and SEM

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.Microstructure of semi-solid billets prepared by new SIMA method is very homogeneous

in which 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 firstly is increased then decreased

and its shape factor approached to one.With increasing in equivalent strain obtained by ECAE

grain size is decreased.