Microstructure evolution and mechanical properties of rheocast A1-5Si-3Cu alloy

Ishak, Nur Hafizah (2017) Microstructure evolution and mechanical properties of rheocast A1-5Si-3Cu alloy. Project Report. Universiti Teknikal Malaysia Melaka, Melaka. (Submitted)

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Abstract

In this study, cooling slope (CS) rheocasting was employed to produce a non-dendritic feedstock of Al-5Si-3Cu. The microstructural evolution of the non-dendritic Al-5Si-3Cu alloys were studied. Besides, the hardness, tensile strength and wear behaviour of cooling slope casting and conventional casting samples were investigated. All the experimental works were carried out by using same Al-5Si-3Cu alloy. Some of the rheocast samples were then treated with a T6 heat treatment that is solution treatment at 520°C for 8 hours, quenching in water, and then followed by aging at 154°C for 4 hours. All of the samples were then characterised by optical microscopy (OM), scanning electron microscope (SEM), hardness tests, tensile test as well as wear tests. X-ray diffraction (XRD) was used to investigate the phases presents in the alloys. The results showed that the CS rheocast Al-5Si-3Cu alloy exhibits the spherical microstructural feature due to all dendritic structures were transform into ɑ-Al globule and rosette. The Vicker’s hardness value revealed that cooling slope rheocasting sample achieved the higher hardness than conventional casting. In addition, it was observed that for ultimate tensile strength (UTS), yield strength (YS) and elongation of the cooling slope rheocasting has the higher value compared to conventional casting which is 218.341MPa for UTS, 151.446MPa for YS and 8.76% elongation. Moreover, the wear behaviour of cooling slope show an improvement as compared to conventional casting. The cooling slope rheocasting that underwent T6 heat treatment showed the positive results in terms of homogenous microstructure distribution, improvement in hardness, tensile properties and wear behaviour as compared to non-heat treated sample.

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