Semisolid microstructural evolution of (CNTs + Sip)/AZ91D powder compacts prepared from powders by cold pressing and remelting

• Published in: Rare metals 2020-06, Vol.39 (6), p.733-742
• Main Authors: Li, Pu-Bo, Tan, Wan-Ting, Gao, Mang-Mang, Liu, Kuan-Guan
• Format: Article
• Language: English
• Subjects: Beta phase; Biomaterials; Chemistry and Materials Science; Coarsening; Cold pressing; Densification; Energy; Evolution; Heat treating; Heating; Liquid phases; Magnesium base alloys; Materials Engineering; Materials Science; Melting; Metallic Materials; Microstructure; Nanoscale Science and Technology; Phase transitions; Physical Chemistry; Powder compacts; Semisolids; Structural integrity; Thixoforming
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-020-01396-3

The evolution of semisolid microstructure during partial remelting of (CNTs + Si p )/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 Mg 2 Si p 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 + Si p )/Mg powder compact. Graphic abstract