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.

Abrasive waterjet machining (AWJM) is a well-known non-traditional cutting process that is widely used to shape materials such as metals, ceramics, alloys, and composites. AWJM was utilized to manufacture titanium alloy in this study, with influencing parameters such as standoff distance (SOD), abrasive flow rate (AFR), and traverse speed (TS) being varied. Material removal rate (MRR) and surface roughness (SR) have been used to quantify the impact of these variables on machining quality. The effects of process factors on output responses were investigated using a Taguchi study approach with an L9 factorial design. SOD of 1 mm, AFR of 300 g/min, and TS of 519 m/s yield the best combination for greater MRR. A combination of SOD of 3 mm, AFR of 400 g/min, and TS of 519 m/s yields the best SR results. Simultaneous optimization of both outputs was also carried out using Taguchi-based Grey relational analysis (GRA) and data envelopment analysis-based ranking (DEAR) methodologies. PCA is utilized for considering the weights of responses and the correlation among them. Both methods obtained similar results, but there is a difference in the middle rankings in the nine experimental trials. Validation trials were run on the acquired combination of parameters, and the error was found to be within acceptable bounds.