搅拌铸造SiCp/2024复合材料热挤压-轧制变形组织及性能

The Hot Extrusion and Rolling Microstructures and Properties of Stir-cast SiCp/2024 Composite

利用搅拌铸造-热挤压-轧制工艺制备SiCp/2024复合材料薄板。通过金相观察(OM)、扫描电镜(SEM)及力学测试等手段研究了该复合材料在铸态、热挤压态及轧制态下的显微组织及力学性能,分析了材料在塑性变形过程中显微组织及力学性能的演变。结果表明,该复合材料铸坯主要由80～100μm的等轴晶组成,粗大的晶界第二相呈非连续状分布,SiC颗粒较均匀地分布于合金基体中;热挤压变形后,晶粒沿挤压方向被拉长,SiC颗粒及破碎的第二相呈流线分布特征;轧制变形后,基体合金组织进一步细化,晶粒尺寸为30～40μm,SiC颗粒破碎明显,颗粒分布趋于均匀,轧制变形对挤压过程中形成的SiC颗粒层带状不均匀组织有显著的改善作用。数学概率统计指出,塑性变形有利于提高颗粒分布的均匀性。力学测试表明,塑性变形后,复合材料的抗拉强度、屈服强度和延伸率显著提高。SiCp/2024铝基复合材料主要的断裂方式为:合金基体的延性断裂、SiC颗粒断裂及SiC/Al界面脱粘。

SiCp/2024 aluminum matrix composite sheets were prepared successfully by stir casting process, rolling after hot extrusion. The microstructures and properties of SiCp/2024 aluminum matrix composite in the as cast, as-extruded, as-rolled condition were investigated by optical microscope（OM）, scanning electronic microscope （SEM） and tensile tests. The evolution on the microstructures and properties during the plastic deformation process was analyzed. The experimental results showed that the as-cast composite was composed of equiaxed grains with the average grain size of 80-100μm and the large coarse phases on the grain boundary were distributed in discontinuity; SiC particles were located homogeneously in the alloy matrix. After hot extrusion process, the grains of the alloy matrix were elongated; the cracked phases and SiC particles were aligned along the hot extrusion direction. After hot rolling process, the composite represented the fine microstructures, the average size of the grain was about 30 40fire. SiC particles were distributed homogeneously in the alloy matrix; the hot rolling process was helpful to modify the non-uniform layered structures formed during hot extrusion process. The mathematic probability statistics showed the degree of uniform distribution of SiC particles in the alloy matrix was improved obviously after plastic deformation. Tensile tests results showed that the plastic deformation process induced a slight increase in ultimate tensile strength, yield strength and elongation. The fracture of SiCp/2024 aluminum matrix composite was mainly resulted from SiC/A1 interface decohesion, SiC particles fracture and matrix ductile fracture.