Lap joints of commercially pure magnesium plates to aluminium plates (Magnesium plate on the top, and Aluminium plate, grade 1100, on the bottom side) were conducted by friction stir welding using various traveling and rotation speeds of the tool to investigate the effects of the welding parameters on the joint characteristics and strength. Defect-free lap joints were obtained in the welding traveling speed range of 40-80 mm/min, and rotational speed range of 1200-1600 rpm. The shear tensile strength of Mg/Al joints increased as a result of decreasing the welding speed from 120 to 40 mm/min at constant rotation speed of 1600 rpm. Defects such as surface grooves, excessive flash, tunnels, and voids were observed if the joints prepared out of the mentioned range. The effects of the welding parameters are discussed metallographically based on observations with optical and scanning electron microscopes.

Despite the increased use of aluminium alloys in several industries, their common concern is the difficulty of joining Dissimilar alloys using welding techniques. Based on this, the primary purpose of this research is to assess the mechanical characteristics of Dissimilar joining of heat-treatable 6061 and non-heat-treatable 5083 aluminium alloys by gas tungsten arc welding and to discover the link between microstructure and mechanical properties. Similar welds were also implemented and evaluated in order to more properly analyze and compare the outcomes. The quality of the weld generated after establishing the health of the joint using non-destructive testing was evaluated by destructive bending, tensile, metallographic, and hardness tests to check the mechanical and microstructural qualities. The intended Dissimilar weld was produced under the parameters of pulse current 120-80 amps, voltage 20 volts, welding speed 15 cm/min, and filler 5356. It should be highlighted that the Dissimilar weld had the maximum joint efficiency, and with perfect control of welding settings and the absence of flaws, only 36% loss of strength was recorded when compared to the base metal. Metallographic images revealed that the formation of hot cracks in the dendritic structure of the weld metal is the major cause of strength loss for 5083 similar weld and the production of numerous porosities in the weld metal for 6061 similar welds.

In this research, microstructure and mechanical properties of AISI316 to AISI430 Dissimilar joint were investigated. For this purpose, GTAW process using ER316L and ER2209 filler metals with diameter of 2. 4 mm was used. The microstructure and fracture surface of the welded samples were characterized by optical microscopy and scanning electron microscopy. Also the mechanical properties of the welded samples were evaluated by tension, impact and microhardness tests. It was found that the microstructure of the welded sample with ER316L filler metal contained widmanstatten austenite with inter-dendritic and lathy ferrite. Also, in the welded sample with ER2209 filler metal, Austenite phase in ferrite matrix was seen. In tension test, all samples were fractured from AISI430 side of the joint in a ductile manner. ER2209 weld metal indicated low impact energy about 27 J, while ER316L weld metal indicated higher impact energy about 43 J. The surface fracture in both welded samples indicated brittle fracture mode. The microhardness of the weld metal of the welded sample with ER316L filler metal was higher than the welded sample with ER2209 filler metal due to the presence of alloying elements, proper distribution of delta ferrite and finer microstructure.

In this research, the microstructure and mechanical behavior of Dissimilar joint of AISI 321 stainless steel to ASTM A57CL1 were studied. For this purpose, the GTAW process and ER 308L filler metal with diameter of 1. 8 mm were used. In order to study the microstructure and fracture surface of weld samples, optical microscope and scanning electron microscope (SEM) were used. Also, the mechanical behavior of the joint was examined by impact, tension and microhardness tests. It was found that the microstructure of weld metal was austenite with skeletal ferrite. Also in some areas the lacy ferrite was seen. All samples were fractured from ASTM A537CL1 steel with a ductile manner during the tension test. The weld metal indicated high impact energy about 205 J.

In the present study, Dissimilar welding between Inconel 718 nickel base superalloy and 310S austenitic stainless steel using gas tungsten arc welding process was performed in order to microstructural characterization and weldability assessment of filler metal used. For this purpose, three filler metals including Inconel 625, Inconel 82 and 310 stainless steel were used. After welding, the microstructure of different regions including base and weld metals were metallographically characterized using the optical and scanning electron microscope equipped with energy dispersive spectroscopy. Moreover, to estimate susceptibility to solidification cracking of weld metals, Varestraint tests were used. Microstructural observations showed that solidification conditions have created a dendritic structure for Inconel 625 weld metal. Moreover, microstructure of the 310 weld metal was consisted of solidification micro-cracks that distributed along the solidification sub grain boundaries. Varestraint test also determined that, at all applied strain, Inconel 82 weld metal has the lowest susceptibility to solidification cracking among the weld metals. Finally, by comparing the results obtained, Inconel 82 filler metal was diagnosed the best choice for mentioned Dissimilar joint.

In the present study, the effects of the length, thickness, welding current, welding sequence, holding time in the fixture and similarity of the base metals on welding residual distortion of Dissimilar joint between carbon steel CK4 and stainless steel AISI409 were firstly investigated on the basis of a verified finite element model. Then, considering the welding current, fixing time and sequence of welding operation, the magnitude of welding residual distortion was minimized. The results showed that in the studied Dissimilar joint, the minimum distortion occurred when the welding current was about 95A; fixing time was 120 sec and symmetric layout was used.

This present study aimed to create an Al6061-St52 Dissimilar joint and investigate the effect of the transverse speed by the friction stir welding process. Welding aluminum to steel is rugged by fusion methods because of the formation of brittle intermetallic compounds (IMCs). Therefore, to designate optimal parameters, acceptable IMC thickness, and mechanical properties determined. This research carried out different three transverse speeds of 16, 40 and 85 mm/min (with a constant pin offset of 0. 2 mm). Geometry of tool's pin radius and height is 4mm and 1. 8mm, respectively. In the transverse speed parameter, the highest ultimate tensile strength (UTS) of 200 MPa was obtained at 85 mm/min. According to the Energy Dispersive X-ray Spectroscopy results, an IMC layer formed in the joint interface. The heat input rate was calculated to designate the optimal parameters. In tensile specimens, fracture mainly occurred in the joints and within the aluminum stir zone due to the combination of thick IMC layer and steel fragments, respectively. The micro-hardness measurement results showed that at (85 mm/min) the hardness values were HV 75 in the aluminum stir zone and HV 315 in the AS vicinity of the interface region. This hardness value is much higher than the base metals (Aluminum base metal is an average of HV 53 and an average steel base metal of HV 245).

Dissimilar weld joints between stainless steels and nickel based super alloys are extensively used in petrochemical, gas and oil applications. These joints jave great challenges from metallurgical transformations point of view. In this research, microstructural evolutions and corrosion behavior of laser weld joint between Inconel 625 and AISI 430 ferritic stainless steel were investigated. Ferritic stainless steels are less expensive and have magnetic properties in comparison with austenitic stainless steels. Scanning electron microscope and optical microscope were used in order to study the microstructures of weld metal and heat affected zone. It was found that fine dendritic microstructuresare formed in the weld metal which isgrown in a competition manner. An epitaxial growth was observed in the interface between AISI base metal and weld metal. No considerable grain growth was observed in the heat affected zone on Inconel 625. Corrosion resistance of weld joint was investigated in 3. 5 % wtNaCl solution using potantiodynamic polarization test. It was concluded that corrosion resistance is increased from AISI 430 base metal toward Inconel 625 base metal.

Using friction heat, welded joints of the Friction stir welding (FSW) process are made that are utilized to forge metal components together. Since there is no parent metal melting, several advantages are obtained by the FSW process over fusion welding. The alloys AA6XXX and AA7XXX Al are two sets of the most extensively utilized structural materials in rail transportation, automotive, and aerospace industries. The objective of present study was to investigate the effects of novel cross-sections in joint lines and further analyze the improvement in mechanical features. Due to the importance of the weld zone properties, many researchers seek to improve the mechanical behavior of the weld zone. For this, friction stir welded joint under four different new design in cross section named E1, E2, E3, E4 and one conventional cross section, E5 were conducted. Better outcomes are obtained by joints made utilizing this method based on joint quality and strength. The very good tensile features are displayed by the fabricated joints with Ultimate Tensile Strength (UTS)> 254 MPa and elongation > 7%. The highest UTS value which is occurred in E3 condition (Downward step) is 24.7% higher than required for FSW of AA6061 alloy at T6 condition in the American Welding Society (AWS) standard (186 MPa).

Microstructural and mechanical properties of Dissimilar bonding of INCONEL 625 and 316L austenitic stainless steel using AWS BNi-2 have been evaluated. The bonding process was done at 1020oC for 30, 60 and 120 minutes, respectively with Argon protection followed by homogenization at the temperature of 1080oC for 4 hour. Chemical analysis from the joint clearance microstructure and mechanical data indicated that the higher the bonding time from 30 to 120 minutes, the lower fraction of precipitates at the joint centerline. Given this, the ultimate shear tensile strength raised from 265 MPa to 360 MPa. Post-bonding homogenization led to more uniform microstructure along with mechanical properties. Moreover, the ultimate shear tensile strength increased to 520 MPa, too.