激光选区熔化纳米SiC/AlSi7Mg复合材料微观组织及力学性能EI北大核心CSCD

采用机械混合法制备纳米SiC/AlSi7Mg混合粉末,利用激光选区熔化技术(selective laser melting,SLM)成形纳米SiC颗粒增强AlSi7Mg复合材料,观察和分析试样的相对密度、物相和微观组织,并测试材料的硬度和拉伸性能。结果表明:SLM成形纳米SiC/AlSi7Mg复合材料试样的相对密度随着扫描速度和扫描间距的增大均呈现先增加后减少的趋势,相对密度最高可达99.75%;试样微观组织与SLM成形铝合金相似,Si相呈网状结构均匀嵌入α-Al基体中,且在Al基体中存在与Si分布相似的纳米SiC团聚物及Mg_(2)Si相;与AlSi7Mg相比,复合材料微观组织由柱状晶转化为等轴晶,且晶粒明显细化(平均晶粒尺寸为1.36μm);由于SiC的加入,产生细晶强化和固溶强化,试样的硬度和强度均明显提高,硬度最高达到137.3HV,抗拉强度达到448.3 MPa,屈服强度达到334.7 MPa,但伸长率下降至3.9%,断裂模式主要为脆性断裂。

Microstructure and mechanical properties of nano-SiC/AlSi7Mg composites fabricated by selective laser melting

The nano-SiC/AlSi7Mg mixed powder was prepared by mechanical mixing method. The specimens of nano-SiC particle reinforced AlSi7Mg composite were fabricated by selective laser melting (SLM). The relative density, phase and microstructure were observed and analyzed, and the microhardness and tensile properties were tested. The results show that the relative densities of SLM nano-SiC/AlSi7Mg composite are increased firstly and then decreased with the increase of scanning speed and scanning space, and the maximum relative density reaches 99.75%. The microstructure of specimens is similar to that of SLM-formed Al-Si alloys, and the network-structured Si phase is uniformly embedded in the α-Al matrix. There are nano-SiC agglomerates and Mg₂Si phase in the α-Al matrix, which has a similar distribution to Si. Compared with AlSi7Mg, the microstructure of specimens is changed from columnar to equiaxed grain, and the grains are significantly refined (the average grain size is 1.36 μm). Due to the addition of SiC, grain refinement strengthening and solid solution strengthening are produced, and the hardness and strength of composite are significantly improved. The hardness, tensile strength and yield strength reach 137.3HV, 448.3 MPa and 334.7 MPa, respectively. However, the elongation is reduced to 3.9%, and the fracture mode is mainly brittle fracture.