往复挤压制备Mg2Si/Mg-Al复合材料组织及时效行为研究

对用石墨型铸造方法制备的Mg2Si/Mg-Al基复合材料进行了多道次往复挤压及时效处理,以探讨该材料组织与硬度的变化规律。结果表明:Mg2Si/Mg-Al复合材料经往复挤压7道次后,Mg2Si相分布均匀且小于30μm,基体晶粒尺寸<10μm,复合材料硬度为150.7HV,与铸态相比提高了22.5%;挤压后的材料经215℃时效6h后,硬度为163.9HV,较铸态提高了33.3%。硬度的提高得益于基体组织、Mg2Si和Mg17Al12的细化,而时效后硬度进一步提高是由于固溶到基体中的Al原子以颗粒状Mg17Al12相析出。

Microstructure and ageing behavior of Mg2Si/Mg-Al composites produced by reciprocating extrusion

Mg2Si/Mg-Al composite prepared by graphite mould casting was reciprocally extruded and subsequently ageing-treated (T5). Variation of the microstructures and the hardness was discussed. The results show that, after being extruded for 7 passes, Mg2Si particles in the Mg2Si/Mg-Al composite distribute uniformly and are less than 30 μm, and the grain size of matrix is less than 10 μm; the hardness of the composite is 150.7HV, which is increased by 22.5% compared with the as-cast alloy; the hardness of 163.9HV is obtained after being held at 215 ℃ for 6 h,33.3% higher than that of as-cast sample. Improvement of the hardness owes to refinement of matrix, Mg2Si and Mg17Al12; reason of the further increase of the hardness after ageing treatment is that Al atoms which solid soluted in the base precipitate in the form of granular Mg17Al12.