半固态搅拌法制备B4Cp／AZ91复合材料热挤压态的组织与性能

Microstructure and Properties of Hot-Extruded B_4Cp/AZ91 Composites Prepared by Semisolid Stirring Method

用半固态搅拌法结合热挤压工艺制备出了颗粒分布均匀、孔隙率低的B4Cp／AZ91颗粒增强镁基复合材料。在经过热挤压后，材料密度为1．873g／cm^3，0-100℃线膨胀系数为19×10^-6K^-1，抗拉强度为282．8MPa。热挤压能显著提高复合材料的致密度，细化基体组织，改善颗粒分布状况，热挤压会对B4C颗粒造成损伤和形成小范围的团簇状聚集，由于挤压变形过程中的协调变形和基体合金的填充机制，不会对材料组织造成损伤，从断口形貌特征上可以确定颗粒与基体间形成了很强的界面结合。

Particulate reinforced magnesium alloy matrix composites B4Cp/AZ91 were successfully fabricated by semisolid stirring method. The experiment results indicated that the B4Cp/AZ91 composites have a uniform B4C particle distribution and excellent properties. After hot-extrusion, the density of B4Cp/AZ91 composites and the tensile strength were 1.873 g/cm^3 and 282.8 MPa respectively. The linearity expansion coefficient was 19×10^-6 K^-1 at 0 to 100 ℃. 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 B4Cp/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.