The effects of welding parameters on the tensile shear strength of refill friction stir spot welding of 7075-T6 aluminium alloy joints

Abstract

The paper presents the results of an analysis of the effect of welding parameters on the load capacity of joints obtained by the refill friction stir spot welding (RFSSW) method. This technology has a prospective application in aerospace and automotive industries, especially for aluminium alloys. The research was conducted for the overlapping joints made of two 7075-T6 aluminium alloy sheets with thicknesses 1.6 mm and 0.8 mm. Strength tests were conducted for two variants of loading the joint. The experiments were conducted according to statistical Hartley’s plan PS/DS-P:Ha3. The welding times t was varied in the range of 1.5 ÷ 3.5 s, the tool plunge depth g in the range of 1.5 ÷ 1.9 mm, and the tool rotational speed n in the range of 2000 ÷ 2800 rpm. For these parameters the analysis of experiment reproducibility, impact significance and adequacy of equations were made. The results of analysis according to the design of the experiment (DOE) indicate that all analyzed parameters have significant influence on the load capacity of joints. The biggest load capacity of joints in the case of the first variant was gained at the maximum spindle speed of 2800 rpm, the minimum tool plunge depth of 1.5 mm and welding time of 1.5 s. For the second variant, the maximum load capacity of joints was gained at the spindle speed of 2400 rpm, tool plunge depth of 1.5 mm and welding time of 2.5 s.