Effects of stirring parameters on the rheocast microstructure and mechanical properties of magnesium alloy

Patrick, Philip (2022) Effects of stirring parameters on the rheocast microstructure and mechanical properties of magnesium alloy. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Semisolid state processing converts as-cast dendritic microstructure into globular nondendritic microstructure with improved mechanical characteristics. The benefits of the rheocasting process, which involves mechanically churning metals in a semisolid state, are linked to processing parameters. Magnesium alloy AM50 is melted and cooled to semisolid processing temperature (610°C) to examine the effects of stirring time and stirring speed. In addition, stirring for 1, 2, 4, and 8 minutes with stirring speeds of 200, 300, 400, and 600 rpm will be performed. To investigate the influence of stirring, cylindrical samples with different diameters will be collected in each experiment. The microstructure of magnesium alloy AM50 was analyzed through OM, SEM, and XRD. Mechanical testing is also conducted to evaluate the properties of the material. A stirring time of 8 minutes with a stirring speed of 600 rpm is optimal during casting to transform the dendritic alloy into a more refined primary solid particle. Higher stirring speed and longer stirring time have uniform size distribution of the primary particles due to little formation of a larger cluster. The intermetallic compounds (Mg17Al12, Al8Mn5) were detected in the microstructure, observed by SEM, and identified via XRD. The intermetallic compounds dissolved into αMg during high stirring speed. The hardness of the alloy was significantly improved by 66.67%, with a value of 100.70 HV. The yield strength of the alloy increased from 124 MPa to 131.05 MPa, while the ultimate tensile strength exhibited an improvement of 9.1%, an increase of 251 MPa, and the elongation to break had substantial growth from 15% to 20%.

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