Recent Developments on UltRasonic cavitation BaseD soliDification pRocessing of BUlk magnesiUm nanocomposites

Magnesium based metal matrix composites (MMCs) have been extensively studied as an attractive choice for automotive and aerospace applications due to their low density and superior specific properties including strength, stiffness and creep resistance. Xi et al [1] studied the Ti6Al-4V particulate (TAp) reinforced magnesium matrix composite which is fabricated by powder metallurgy route. The tensile strength of the composite was markedly higher than that of the unreinforced magnesium alloy. Xi et al [2] also studied the SiC whiskers-reinforced MB15 magnesium matrix composites by powder metallurgy and found that the mechanical properties of SiCw/MB15 composite were significantly influenced by powder-mixing methods of PM. Li et al [3] studied the hot deformation behavior of SiC whiskers reinforced AZ91 magnesium matrix composites in compression. It was found that the microstructure evolutions involved the movement of SiC whiskers and the changes of the matrix, and the rotation and the broken SiC whiskers tended to be obvious with the increasing strain, and also high density of dislocation was observed in the AZ91 matrix at the initial stage of compression (1%). Jiang et al [4] studied that magnesium metal matrix composites (MMCs) reinforced with B4C particulates fabricated by powder metallurgy. The hardness and wear resistance of the composites were higher than those of as-cast Mg ingot and increased with increasing amount of B4C particulates from 10 to 20 vol.%. Zhang et al [5] studied that carbon nanotube reinforced magnesium metal matrix composite by stirring the carbon nanotube into magnesium melts. It was found that carbon nanotube, especially chemical nickel-plated one, This paper presents the results from our recent development in cast bulk Mg nanocomposites. SiC nanoparticles reinforced magnesium and magnesium alloys including pure magnesium, and Mg-(2, 4)Al-1Si and Mg-4Zn were successfully fabricated by ultrasonic cavitation based dispersion of SiC nanoparticles in magnesium melt. As compared to un-reinforced magnesium alloy matrix, the mechanical properties including tensile strength and yield strength were improved significantly while the ductility was retained or even improved. In the microstructure, the grain size was refined considerably by SiC nanoparticles. While some micro SiC clusters still exist in the magnesium matrix, ultrasonic cavitation based processing is very effective in dispersing SiC nanoparticles. A SEM study showed that SiC nanoparticles were dispersed quite well in the areas outside micro SiC clusters. A TEM study on the interface between SiC nanoparticles and magnesium alloy matrix indicates that SiC nanoparticles bonded well with Mg matrices without forming an intermediate phase.