Microstructure Evolution and Mechanical Properties of Mg2B2O5 Whiskers Reinforced AZ31B Magnesium Composites Extruded at Elevated Temperatures

Abstract

The microstructure evolution and mechanical properties of Mg2B2O5 whiskers reinforced AZ31B magnesium composite during extruded were investigated using optical microscope and scanning electron microscope. Mg2B2O5w/AZ31B was fabricated by stir-casting and the as-cast ingot was machined into cylindrical billets. Then the hot extrusion was carried out at 350°C at a constant speed of 10 mm/s with extrusion ratio of 6.25:1. The mechanical properties (strength, ductility and hardness) were tested by tensile tests and hardness tests at room temperature. Typical microstructures of different positions of extruded stock showed the microstructure evolution law during extrusion processing. It was found that DRX took place and whiskers accelerated DRX during hot extrusion. The whisker distribution in the composites was improved by hot extrusion. Additionally, the vickers microhardness of the composites increased first, and then decreased with deformation degree increased.