Microstructure and properties of hot-extruded B₄C_p/AZ91 composites prepared by semisolid stirring method

Particulate reinforced magnesium alloy matrix composites B₄C_p/AZ91 were successfully fabricated by semisolid stirring method. The experiment results indicated that the B₄C_p/AZ91 composites have a uniform B₄C particle distribution and excellent properties. After hot-extrusion, the density of B₄C_p/AZ91 composites and the tensile strength were 1.873 g/cm³ and 282.8 MPa respectively. The linearity expansion coefficient was 19×10^-6 K^-1 at 0 to 100 °C. Hot-extrusion can significantly improve density, particle distribution of composites and refine the B₄C particles. After hot-extrusion, the small scale conglomerations of B₄C particles would not impair the microstructure and properties of B₄C_p/AZ91 composites because of inflation mechanism of matrix alloy and coordinated deformation between particles and matrix. Moreover, analyses of fractures indicated that the higher bond strength interface was formed between particles and matrix alloy after hot-extrusion process.