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The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080${}^{\circ }$C, 1150${}^{\circ }$C and 1200${}^{\circ }$C with 15min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080${}^{\circ }$C followed by water quench and at 1150${}^{\circ }$C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov–Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100${}^{\circ }$C and that for oil quenching was around 1140${}^{\circ }$C. The pit depths were found to be in the range of 100nm and width of 1.5–2$\mu$m.

The main purpose of the current research work is to identify and investigate a novel method of holding an intermediate metal and to evaluate its metallurgical and mechanical properties. Copper was used as an interlayer material for the welding of this dissimilar Ti–6Al–4V (Ti alloy) and 304L stainless steel (SS). The study shows that the input parameters and surface geometry played a very significant role in producing a good quality joints with minimum heat affected zone and metal loss. A sound weld was achieved between Ti–6Al–4V and SS304L, on the basis of the earlier experiments conducted by the authors in their laboratory, by using copper rod as intermediate metal. Box–Behnken method was used for performing a minimum number of experiments for the study. In the present study, Ti–6Al–4V alloy and SS304L were joined by a novel method of holding the interlayer and new surface geometry for the interlayer. Initially, the drop test was used for determining the quality of the fabricated joint and, subsequently, non-destructive techniques like radiography and C-scan were used. Further optical micrograph, SEM–EDS, hardness and tensile test were done for understanding the performance of the joint.

In aerospace industry, there is a need for aluminum/titanium joints in wing spars of aircraft structures. This research explores the feasibility of joining Ti6Al4V to AA6061 by means of friction welding. Influence of geometrical design on the microstructure and impact strength of dissimilar AA6061/Ti6Al4V joints is investigated. Investigation by scanning electron microscopy reveals deformation of the grains at titanium side along the direction of stress, therefore leading to the formation of TMT (thermo-mechanically treated) zone. The intermetallic compound at the joint interface is attributed to the presence of brittle TiAl and Ti₃Al phases. Rotational speed has a significant influence on the impact strength. The impact energy at the interface was found to be 10.2J when the speed of rotation was set as 1000rpm. Geometry featuring “spearhead with blunt end” is found to give good joint strength with minimum material loss. Fractography studies reveal the presence of few dimples in the welded zone and brittle mode of fracture.

The welding community faces a challenging problem in choosing the best welding methods since they are multi-input processes. Modern manufacturing industries have requirements to get fast and optimum process parameters to utilize complete resources in an optimum way. This work attempts to improve the performance of submerged arc welding (SAW), friction welding (FW), and gas tungsten arc welding (GTAW) processes by optimizing their parameters. The newly developed Rao algorithms and their modified versions known as quasi-oppositional Rao (QO Rao), self-adaptive multi-population elite Rao (SAMPE Rao), and improved Rao (I-Rao) are used. This paper contains four multi-objective optimization case studies of SAW, FW, and GTAW processes. A weighted approach is employed to tackle the multi-objective optimization problems effectively. The outcomes achieved using the Rao, QO Rao, SAMPE Rao, and I-Rao algorithms are compared with those obtained by the established optimization algorithms such as accelerated cuckoo optimization algorithm (ACCOA), cuckoo optimization algorithm (COA), plant propagation algorithm (PPA), teaching–learning-based optimization (TLBO) algorithm, Jaya algorithm, quasi-oppositional Jaya (QO Jaya) algorithm, genetic algorithm (GA), particle swarm optimization (PSO) algorithm, and heat transfer search (HTS) algorithm. The effectiveness of the Rao algorithms and their modified versions has been clearly demonstrated as these algorithms have provided superior solutions while requiring fewer generations to achieve them.

Joining of metal with ceramics has become significant in many applications, because they combine properties like ductility with high hardness and wear resistance. By friction welding technique, alumina can be joined to mild steel with AA1100 sheet of 1mm thickness as interlayer. In the present work, investigation of the effect of friction time on interlayer thickness reduction and bending strength is carried out by factorial design. By using ANOVA, a statistical tool, regression modeling is done. The regression model predicts the bending strength of welded ceramic/metal joints accurately with ± 2% deviation from the experimental values.

The joining of ceramic and metals can be done by different techniques such as ultrasonic joining, brazing, transient liquid phase diffusion bonding, and friction welding. Friction Welding is a solid state joining process that generates heat through mechanical friction between a moving workpiece and a stationary component. In this article, numerical simulation on thermal analysis of friction welded ceramic/metal joint has been carried out by using Finite Element Analysis (FEA) software. The finite element analysis helps in better understanding of the friction welding process of joining ceramics with metals and it is important to calculate temperature and stress fields during the welding process. Based on the obtained temperature distribution the graphs were plotted between the lengths of the joint corresponding to the temperatures. To increase the wettability, aluminium sheet was used as an interlayer. Hence, numerical simulation of friction welding process is done by varying the interlayer sheet thickness. Transient thermal analysis had been carried out for each cases and temperature distribution was studied. From the simulation studies, it is found that the increase in interlayer thickness reduces the heat affected zone and eventually improves the joint efficiency of alumina/aluminum alloy joints.