Abstract
The grain refinement of AlN particles reinforced AZ91D Mg-based metal-matrix composites (MMCs) was investigated in this paper. The Mg MMCs were prepared by the melt-stirring technique with addition of 1, 2 and 5wt.% of 1 µm AlN particles. Observing the microstructures of MMCs, the β-phase of Mg was almost eliminated through homogenisation. The ultimate tensile strength of Mg MMCs with only 1wt.% addition of AlN_p has increased to 174 MPa, which is by 10.1 % higher than that of pure AZ91D. After homogenisation, the ultimate tensile strength of Mg MMCs with 1wt.% addition of AlN_p has increased to 253 MPa, which is by 60.1 % higher than that of pure AZ91D.

Key words
grain refinement, metal-matrix composites, homogenisation, tension test

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