The impact of backing plate thermal conductivity on mechanical properties of friction stir spot welded AA 5052-H32 joints

The study aims to evaluate the effectiveness of Friction Stir Spot Welding (FSSW) as a replacement for Resistance Spot Welding (RSW) in industrial applications by joining 5052-H32 aluminium alloy plates and standard JIS G 3136 steel.The variables in the study included a granite backing plate, AISI 1010 steel, and Al-Si alloy, with fixed welding parameters: a rotational speed of 1000 rpm, a dwell time of 5 seconds, and a plunge depth of 0.2 mm. The study analysed the impact of the thermal conductivity of the backing plate on the hardness and tensile shear load of the FSSW joints. Welding temperatures were recorded as 167.37C for granite, 113.18C for AISI 1010 steel, and 100.88C for Al-Si.The study found that increased thermal conductivity of the backing plate resulted in harder weld joints. The Vickers hardness values were recorded as 36.5 HVN for granite, 47 HVN for AISI 1010 steel, and 49.5 HVN for Al-Si. The size of the nugget influences the tensile shear load. The granite backing plate generates an average tensile shear load of 3986.98 N, Steel AISI 1010 3769.00 N, and Al-Si. 3414.32 N.The research is limited to the specific materials and parameters used in the study. Further research could explore different materials and varying parameters to expand the applicability of the findings.The findings suggest that selecting backing plate materials with higher thermal conductivity can enhance the hardness and tensile shear load of FSSW joints, providing valuable insights for industrial applications.The study contributes to the existing body of knowledge by demonstrating the potential of FSSW to replace RSW in joining dissimilar materials, specifically aluminium, and steel, and by highlighting the significant role of backing plate thermal conductivity in determining joint properties.