Dissimilar friction stir spot welds (FSSW) between the magnesium and aluminum alloys are joined, using a novel approach called refill friction stir spot welding. The present work aims to evaluate the macrostructural and mechanical properties of refill friction stir spot welded AZ31B and AA 6061-T6 alloys in two combinations, i.e., identical Mg-to-Mg and dissimilar Mg-to-Al joints, and the results are compared with the results obtained in conventional friction stir spot welding. The hardness profiles of the similar welds had the appearance of a W-shape, and the Thermo mechanically affected zone and heat-affected zone of both methods had lower hardness values than the rest of the weld. Along with the interface between the aluminum and magnesium sheets, a thin intermetallic compound layer of Al₁₂Mg₁₇ has been identified, which has led to an increase in hardness. The static shear strength of both similar and dissimilar refill spot friction welds was much greater than that of traditional spot friction welds. In both similar and dissimilar spot friction welds, two distinct failure scenarios are discovered.

The need for additive manufacturing (3D printing) to create near net shape components from a wide variety of materials has grown in recent years. There are several additive manufacturing methods to build various parts by different materials. However, it is challenging to construct, the components with incompatible materials combination for high temperature and creep resistance using conventional methods. Consequently, the purpose of this research is to investigate the use of solid state welding (friction welding) in additive manufacturing (SSAM) of incompatible materials, namely alloy Cr18-Ni8 and 42CrMo4 low alloy alternative layers. The interface bonding strength must be strengthened to achieve the desired isotropic characteristics and high strength for the components. Due to the low temperature at the bonding interface, secondary phases cannot develop when solid state welding is used. In order to obtain the highest bonding strength, optimal process parameters were examined using design of experiments (DOE) with Box–Behnken design model and analysis of variance (ANOVA). The major process parameters of upset pressure, friction pressure and burn-off length were varied to obtain the optimal conditions. In addition, the bonded interfaces were examined by the microstructural characteristics as well as mechanical properties such as micro-hardness and bonding strength. The interface is made up of alloys intermixed with different zones such as a dynamically recrystallized zone and a thermomechanical affected zone. The intermixed layers revealed the migration of C and Mo to Cr18-Ni8 alloy and separated the Fe and Ni bands. The fractography analysis revealed ductile and slightly brittle fracture surfaces with a mixed mode. The relationship between bond strength and interface thickness was determined by studying the impact of interface thickness on bond strength.

Current paper shares the study on optimization of parameters for GTAW and FSW Aluminum alloys. Base metals chosen were AA6061 and AA7075, filler metal used for TIG welding is AA4043. Welding Current, Welding speed and gas flow rate were taken as input parameters for GTAW and axial load, weld speed and tool rotation were choosen as variables for FSW. L9 orthogonal array is used for design of experiments. Analysis of variance is used for ranking the parameters. It was found that an average tensile strength of 127MPa is found for GTAW samples and 151 MPa for FSW samples. Thus an overall 19% increase in strength is achieved. Micro structural analysis is done to investigate the reason for variation of strength. It was found that the formation of Mg-Si precipitates has affected the increase in strength for FSW samples.