Kinetics of SIMA AZ80 Magnesium Alloy

Semi-solid feedstock of AZ80 magnesium alloy modified by [trace] rare-earth Y element 10 (0, 0.2, 0.4, 0.8 wt.%) were fabricated by [strain-induced melting activation] (SIMA) in the form of 11 extrusion and partial remelting. The effect of Y addition on the microstructure evolution of [the] 12 extruded and [isothermally heat] treated alloy was observed by [using an] optical microscope (OM), 13 scanning electron microscope (SEM), X-ray diffraction (XRD) and quantitative analysis. The results 14 show that the Y addition can refine the microstructure and make the β-Mg17Al12 phases 15 [agglomerate]. During the subsequent isothermal treatment at 570°C, the average solid grain size, 16 shape factor and liquid fractions increased with [the] prolonged soaking time. [The] smaller 17 spheroidal solid grains and the larger shape factor were obtained [in the semi-solid microstructure] 18 due to Y addition. The coalescence and Ostwald ripening mechanism operated the coarsening 19 process [of solid grains] simultaneously. The coarsening rate constants of AZ80M1 (0.2 wt.% Y 20 addition) of 164.22 μm3s-1 was approximately four times less than the un-modified AZ80 alloy of 21 689.44 μm3s-1. In contrast, the desirable semi-solid structure featured [with the] fine [and] well 22 globular solid grains, [an] appropriate liquid fractions and shape factor was achieved in AZ80M1 23 alloy treated at 570°C for 20-30 min. 24