The evolution of semisolid microstructure during partial remelting of (CNTs + Sip)/AZ91D powder compacts prepared by cold pressing was studied. The results indicate that rapid grain coarsening is driven by the dissolution of eutectic β phase material during the initial heating period of 0–10 min, so the AZ91D powders with fine equiaxed grains surrounded by intergranular eutectic phases evolve into compact particles. As the heating time proceeds, α-Mg particles were gradually separated by liquid due to the phase transformations of α-Mg + β → L and α-Mg → L. The primary particles coarsened rather slowly and the as-received Mg powder evolved into nearly spheroidal particles surrounded by liquid phase after partial remelting. The in situ synthesized Mg2Sip were distributed homogeneously around the CNTs with maintained structural integrity during partial remelting. Moreover, this microstructural evolution was accompanied by densification through pore filling. An ideal semisolid ingot suitable for thixoforming can therefore be obtained by partially remelting a (CNTs + Sip)/Mg powder compact.

中文翻译：

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(CNTs + Sip)/AZ91D 粉末压块的半固态微观结构演变由粉末通过冷压和重熔制备

研究了冷压制备的 (CNTs + Sip)/AZ91D 粉末压块在部分重熔过程中半固态微观结构的演变。结果表明，在 0-10 分钟的初始加热期间，共晶 β 相材料的溶解驱动了快速晶粒粗化，因此具有细小等轴晶粒的 AZ91D 粉末被晶间共晶相包围，演变成致密的颗粒。随着加热时间的延长，由于α-Mg + β → L 和α-Mg → L 的相变，α-Mg 颗粒逐渐被液体分离。初级颗粒粗化相当缓慢，原样的镁粉演变成部分重熔后被液相包围的近球形颗粒。原位合成的 Mg2Sip 均匀分布在碳纳米管周围，在部分重熔过程中保持结构完整性。此外，这种微观结构的演变伴随着孔隙填充的致密化。因此，可以通过部分重熔 (CNTs + Sip)/Mg 粉末压块来获得适用于触变成形的理想半固态锭。