采用一种结合BC、BA路径特点的改进型路径BC-UD2、在250℃对铸造Al-10.9％Mg2Si原位复合材料进行等通道转角挤压(ECAP)来细化组织、改善Mg2Si增强相形态及分布状态,考察其对力学性能的影响.结果表明:经BC-UD2路径8道次ECAP挤压后,复合材料基体由约100 μm发达的树枝晶组织细化为约1.5 μm的细晶粒组织；原先粗大的汉字状共晶Mg2Si相被细化为约0.85 μm的多边形状颗粒,趋于均匀分布状态,较常规BC路径中Mg2Si颗粒沿基体晶界聚集分布状态有很大改善;经BC-UD2路径挤压后复合材料的抗拉强度由铸态的166.9 MPa增大到331.8 MPa,伸长率由铸态的0.43％增加到23.6％,分别提高了99％和5 400％;同时也比BC路径挤压材料的抗拉强度(297.3 MPa)提高了12％,伸长率(15.15％)提高了56％,综合力学性能显著提高.%A modified equal channel angular pressing (ECAP) route Bc-ud2 combining with the characteristics of routes Be and BA was employed to process an as-cast Al-10.9%Mg2Si in-situ composite at 250 °C to refine the microstructure and modify the morphology and distribution of Mg2Si reinforcements. The results show that after 8-pass ECAP processing the matrix is significantly refined from its original developed dendrites of about 100 μm in the as-cast state to equiaxed grains of about 1.5 μm, and the eutectic Mg2Si from coarse Chinese script cells to fine discrete polygonal particles of about 0.85 μm which are redistributed more homogeneously than those by the conventional route Bc, where the refined Mg2Si particles still congregate seriously along the matrix grain boundary. Accordingly, the ultimate tensile strength and the elongation of the composite processed by route Bc-uD2 are enhanced from 166.9 Mpa and 0.43% in the as-cast state to 331.8 Mpa and 23.46%, increased by 99% and 5 400%, respectively, and further increased by 12% and 56% when compared to those by route Bc, and thus the comprehensive mechanical properties are enhanced remarkably.
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