Mircostructural morphology and mechanical properties of rheocast A319 aluminium alloy

Mohamed Hairi, Mohamed Azelan (2016) Mircostructural morphology and mechanical properties of rheocast A319 aluminium alloy. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

A319 aluminium alloys are widely used in automotive industry as it has a good fluidity and also good mechanical strength. In this study, conventional casting and cooling slope casting has been studied to evaluate the microstructure and mechanical properties. Raw material of A319 aluminium alloy was melt using silicon carbide crucible furnace. For conventional casting, the temperature used was 700°C and directly poured into the mould. For cooling slope process, the temperature used were 650°C, 670°C, and 690°C while the cooling slope length were 200 mm, 300 mm and 400 mm. From the conventional casting, one of the specimens was undergone heat treatment and for cooling slope casting three specimens was used. Then CNC turning was used to cut the specimen. The specimens were examined using optical microscope. Microstructure analysis for non-heated specimens in conventional casting has shown a dendritic primary phase whereas cooling slope casting produce a globular microstructure. The heat treated specimens for both processes produce a precipitation among the phase. The specimen is then undergo hardness test using Vickers hardness tester by applying 100kg load and 1/16 inch diamond ball. The result for non-heated specimen of conventional casting is 81.1 HV and it increased up to 95.75HV in cooling slope casting process. It has proved that heat treatment specimen in cooling slope casting has a better result and the value for the hardness was 131.53HV. For tensile test, the dog bone shape was examined using Universal Tensile Machine. For conventional casting the yield strength, ultimate tensile strength and percent elongation were 140.1 MPa, 233.5 MPa and 2.0% respectively. The yield strength, ultimate tensile strength and percent elongation for non-heated specimen in cooling slope were 165.6 MPa, 237.5 MPa and 2.8% respectively. For heat treated specimen, conventional casting achieved yield strength, ultimate tensile strength and percent elongation 187.2 MPa, 234.9 MPa and 3.3% respectively. For cooling slope, shown yield strength, ultimate tensile strength and percent elongation it achived 204.1 MPa, 241.8 MPa and 3.6% respectively. In conclusion, it is found that cooling slope process is better than conventional casting. Moreover, the heat treated specimen has developed greater performance in mechanical properties of the studied alloy.

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