热挤压温度对混杂增强铝基复合材料的性能及结构影响

The Effects of Hot Extrusion Temperature on the Properties and Microstructure of Aluminum Matrix Composites Hybrid Reinforced

6061铝合金半固态温度区间为582℃~652℃,宜采用半固态法制备6061铝基复合材料.主要研究不同热挤压温度对半固态法制备的5vol%Al18B4O33晶须与15vol%SiC颗粒混杂增强6061铝基复合材料的棒材表面、致密度及力学性能的影响,采用SEM分析材料微观组织结构及拉伸断口形貌,探讨不同挤压温度对材料力学性能影响的原因.结果表明,630℃温度下挤压成型获得的复合材料表面粗糙且有明显孔洞,650℃温度下挤压材料表面存在周期性裂纹,在640℃下挤压可获得表面光滑气孔较少的复合材料棒材.640℃挤压温度下获得的复合材料综合力学性能最佳,抗拉强度为308.9MPa,屈服强度为203.3MPa,延伸率为3.61%,630℃挤压复合材料中较多的孔洞微缺陷造成应力集中,650℃挤压基体晶粒长大粗化且增强体分布不均.

The semi-solid temperature interval of the 6061 aluminum alloy is 582℃~652℃and this is favorite for shaping reinforced aluminum matrix composites.In this paper,the different hot extrusion temperatures were employed to produce and shape the aluminum matrix composites hybrid reinforced with 5vol%Al18B4O33 whiskers and 15vol%SiC particles,and the effects on the surface,density and mechanical properties were investigated.In addition,the microstructure and tensile fracture morphology were characterized by SEM,and the reasons why the different extrusion temperatures can influence the mechanical properties of the composites were investigated.The results showed that when the composites was extruded at 630℃its surface was rough and with obvious holes,when the extrusion temperatures was 650℃there were periodic cracks on the surface and the outside of the composite bar extruded at 640℃was smooth and with less porosity.The composite extruded at 640℃behaved the excellent mechanical properties,its tensile strength was 308.9MPa,the yield strength was 203.3MPa and the elongation was 3.61%.The micro-defects of holes existed in the composites extruded at 630℃caused the stress concentration,and when the composite was extruded at 650℃its grain sizes of the matrix were coarsened and the reinforcement phase were not uniform distributed.