Effect of partial remelting on microstructure and mechanical properties of thixoformed aluminium alloys

Azlan, Diana Annasuhah (2022) Effect of partial remelting on microstructure and mechanical properties of thixoformed aluminium alloys. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

The results of experimental investigations performed with LM 2 l/A308 aluminium alloy are presented. The microstructure of the material during partial remelting in the semisolid state is investigated from different processes experienced by the material and the properties are compared. T)le variables examined were stirred casting process, thixo-forming process and thixo-forming with heat treatment process. Along with microstructural analysis Scanning Electron Microscope (SEM) and the mechanical tests were performed including tensile test and hardness test (Vickers). Based on the experimental findings, it was obtained that partial re-melting can also obscure the structure. Scanning Electron Microscope allows microstructure characterization to determine as-cast process produced a non-dendritic microstructure with 500 rpm stirring speed, thixoformed near-spheroidal microstructure and thixoformed T6 heat treated was fully globule while tensile test allows thixoformed T6 heat treated specimen to have the highest value of Ultimate Tensile Strength (MPa), Yield Strength (MPa) and Elongation to Fracture(%) of258.77 MPa, 134.36 MPa and 8.93% respectively. The hardness test showed thatT6 heat treated specimen improved the morphological properties with 128.4 HV due to the refinement and globularization of structural micro-constituents witl1 non-dendritic structures. The positive effect of structural microstructure obscures the negative porosity effect on property enhancement. It is suggested that reinforcement materials are to be discharged in the matrix to improve the hardness, and ductility with higher reinforcement to weight percentage. In addition, by increasing the stirring time and stirring speed is also able to improve the strength of the material.

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