利用铜模喷铸与高真空感应熔炼技术,制备出不同冷速条件下纳米SiC_p增强AZ91合金非平衡凝固试样。结合400℃等温固溶处理,系统研究了纳米SiC_p颗粒对镁合金凝固组织细化及热稳定性的影响。结果表明,铜模快冷作用下,纳米SiC_p使得镁合金的晶粒尺寸得到显著细化。当铜模内径为2mm时,1%的SiC_p纳米颗粒添加后AZ91合金晶粒尺寸能细化至5μm。SiC_p在合金凝固过程中既作为异质核心又能钉扎晶界阻碍晶粒生长,两者共同作用导致晶粒尺寸明显细化。细晶镁合金经400℃不同时间固溶处理后结果发现,添加纳米SiC_p的合金高温条件下晶粒生长缓慢,保温8h后平均晶粒尺寸仅为12μm,亚稳细晶组织的热稳定性得到有效提高。 Copper casting and high vacuum induction melting technology were used to prepare non-equilibrium solidified samples of nano-SiC_p reinforced AZ91 alloy under different cooling rates. Combined with 400 ℃ isothermal solution treatment, the effects of nano-SiC_p particles on the microstructure and thermal stability of magnesium alloy were systematically investigated. The results show that the grain size of magnesium alloy is significantly refined by the nano-SiC_p under the fast cooling effect of copper mold. When the copper mold inner diameter is 2mm, the grain size of AZ91 alloy can be refined to 5μm after the addition of 1% SiC_p nanoparticles. In the process of solidification, SiC_p can not only serve as a heterogeneous core but also pinch the grain boundaries to hinder the grain growth. The combined effect of these two factors leads to the grain refinement. After heat treatment at 400 ℃ for different time, it was found that the grain growth of the alloy with nano SiC_p was slow at high temperature, the average grain size was only 12μm after 8h incubation, and the thermal stability of metastable fine grained structure was obtained Increase effectively.