Structural and mechanical properties of friction stir welded Al2O3 and SiC reinforced Al 7075 alloys

Abstract

Al 7075 of 4 mm thickness plates were welded by using ceramic particles of micron size. Different revolution speed, ranging from 1600 to 2000 RPM and transverse speed of 17 to 35 mm/min were applied. The sound weld is achieved at revolution speed of 1600 RPM and transverse speed of 17 mm/min. In this work, ceramic particles of Al2O3 and SiC were used to reduce the effect of the heat towards the base material during friction stir welding owing to their high friction coefficient and reasonable thermal conductivity and to enhance mechanical properties. Vickers microhardness test was performed on the plain, Al2O3, and SiC mixed Al 7075 welded samples. This test showed the welded joint by using Al2O3 and SiC have 10 to 12 % increase in hardness than that of the joint without using particles. Tensile strength of welded joints without ceramics particles showed improved results. Dispersion of ceramics particles was examined by metallurgical microscope. Scanning electron microscope (SEM) images and fracture analysis of the stir welded zone and base materials were observed. The structural-property relationship of plain, Al2O3, and SiC mixed Al 7075 welded samples was discussed systematically and found that improvement in hardness for Al2O3, and SiC mixed Al 7075 welded samples was due to the higher thermal conductivities of added ceramic particles and precipitation strengthening mechanism. While, reduction in tensile strength ascribed to the formation of intermetallic compounds.