中文摘要：

采用原位反应近液相线铸造方法制备含有少量原位TiC颗粒的7075铝基复合材料，通过透射电镜观察合金中的原位TiC颗粒的分布与形貌，并利用平均截线法测量晶粒尺寸，研究原位颗粒对近液相线铸造7075铝合金铸态组织形成机制的影响。结果发现，原位TiC颗粒比较均匀地分布于基体合金中，尺寸分布于0．3～0．9μm范围内，形貌呈多边形。随着原位TiC颗粒含量的增加，复合材料的铸态组织由蔷薇状组织逐渐转变为等轴晶组织，当原位TiC颗粒的体积分数达到2．5％时，复合材料的平均晶粒尺寸为35．6gm。

英文摘要：

The microstructures of irrsitu reactive near-liquidus cast 7075＋X% （volume fraction） TiC （X=0, 0.5, 1.2, 2.5） A1 matrix composites were observed using OP. the distribution and morpholo- gy of in-situ TiC particles in matrix of 7075 A1 alloys were observed by TEM and the average grain sizes were measured using a mean linear intercept method. Effect of irrsitu TiC particles on mechanism of formation of microstructure of near-liquidus cast 7075 A1 alloy are analyzed. The result shows that as-cast microstructures of the irt-situ processed composites reveals a relatively uniform distribution of TiC particles with an average size of region of 0.3-0.9μm and the TiC particles had an angular morphology. The rose flowered structure gradually turned into equiaxed, nondendritic structure with increasing of volume fraction of ircsitu TiC particles, whiles TiC particles volume fraction up to 2.5 %, the average grains size of composite was 35.6μm.