Comparison of mechanical properties and microstructure of AZ91D alloy motorcycle wheels formed by die casting and double control forming

摘要

A double control forming technology of motorcycle wheel was firstly developed to form the complex parts with high mechanical properties. The mechanical properties and microstructure of the AZ91D magnesium alloy motorcycle wheels formed by double control forming and die casting was compared. The results of numerical simulation showed that the velocity magnitude in wheel rib was small than that in other positions. The pressure and temperature decreased from the wheel hub to the overflow launders. Large surface defect concentration indicated the oxides and entrapments existed mainly in the well-designed overflow launders. The experimental results confirmed that the motorcycle wheel's complex shape can be achieved by the high-speed filling in the injection procedure and the mechanical properties of the parts were greatly improved due to the forging pressure. It isclear from the micrographs that the high pressure caused by forging system results in obvious grain refinement of the primary α-Mg and uniform distribution of the eutectic consisting of the eutectic α-Mg and β-Mg_(17)Al_(12). Higher mechanical properties including ultimate tensile strength of 246 MPa, elongation of 9.5% and Vicker-hardness of 87.9 were obtained in the parts formed by double control forming due to the fine and uniform micro-structure without defects in comparison to die casting.