Evaluation of Microstructure and Mechanical Properties in Dissimilar Joint of SSM7075 with SSM356 Aluminum Alloy using Diffusion Bonding

The aim of this study is to investigate joining parameters that affect microstructure and mechanical properties of diffusion bonding technique in dissimilar joints between SSM7075 and SSM356 aluminum alloys. Diffusion bonding methods were investigated by joining parameters as follows: contact pressure at 3 MPa, holding time 60 and 120 minutes and temperature at 673, 723, 773 and 823 K respectively, under argon atmosphere at 4 litres per minute. After experiments, the results of the investigation have shown that a condition used contact pressure at 3 MPa, holding time 120 minutes, and temperature at 773 K is complete and no defects and voids. Examination of the joint region using SEM and EDX showed that the microstructure in weld zone after welding is globular structure, and eutectics phases of two materials diffuse together. In weld zone, it was found that formation of eutectic phases has Al2CuMg, Mg2Si and Al2Mg2Zn3 phases along the bond interface, distributed throughout bond interface. The tensile tested showed the maximum tensile strength of 94.94 MPa. The hardness was tested for optimum hardness value, 121.20 HV. However, the heat during welding, resulting in precipitation within the aluminum matrix (α-Al), led to increased hardness after diffusion bonding

A Study of the Essential Parameters of Friction-Stir Spot Welding That Affect the D/W Ratio of SSM6061 Aluminum Alloy

This study aimed to investigate how the depth-to-width (D/W) ratio of the welding area affects the welding quality of the SSM6061 aluminum alloy via the friction-stir spot welding (FSSW) process. The results showed that a higher D/W ratio directly results in better mechanical properties. If the D/W ratio value is high (at 1.494), then this leads to higher tensile shear strength at 2.25 kN. On the other hand, if the D/W ratio values are low (at 1.144), then this reduces tensile shear strength to 1.17 kN. The fracture surface behavior on the ring zone also affects the characteristics of ductile fracture. During Vickers hardness analysis, the hardness profiles are in the shape of a W; the maximum hardness was 71.97 HV, resulting from the rotation speed of 3500 rpm and the dwell time of 28 s, where the hardness of the base metal was at 67.18 HV. Finite element (FEM) analysis indicated that the maximum temperature during simulation was 467 °C in the region near the edge shoulder tool, which is 72.96% of the melting point. According to FEM simulation, the temperature under the tool pin region was 369 °C. The generated heat was sufficient to induce changes in the microstructure. For microstructure changes, the globular grain took on a rosette-like form, and coarse grains were observed in the thermal mechanical affect zone (TMAZ) and in the nugget zone (NZ), transforming in the mix zone. Hooks, kissing bonds, voids, and porosity are the defects found in this experiment. These defects indicate a discontinuity in the NZ that leads to worse mechanical properties. During examination via SEM and energy dispersive X-ray (EDX) analysis, the recrystallization structure from β-Mg2Si IMCs to Al3Mg2 and Al12Mg17 IMCs was observed. The size was reduced to an average width of 1–2 µm and an average length of 2–17 µm. Simultaneously, the oxides from the ambient atmosphere present during welding showed dominant partial elements from SiO2, MgO, and Al2O3

Transient Liquid Phase Bonding of Semi-Solid Metal 7075 Aluminum Alloy using ZA27 Zinc Alloy Interlayer

Transient Liquid Phase Bonding (TLPB) process of semi-solid metal 7075 aluminum alloys (SSM7075) using 50 μm thick of ZA27 zinc alloys as interlayers for the experiment were carried out under bonding temperatures of 480 and 540 °C and bonding times of 30, 60, 90 and 120 min respectively. In the bonding zone, the semi-solid state of ZA27 zinc alloy interlayers were diffused into the SSM7075 aluminum alloy. Examination of the bonding zone using Scanning Electron Microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDS) showed that the precipitation of the intermetallic compound of η(Zn–Al–Cu), β(Al2Mg3Zn3), T′(Zn10Al35Cu55) and MgZn2 were formed in the bonding zone. The better homogenized microstructure in the bonding zone was formed when increasing bonding time and bonding temperature. The highest bonding strength was recorded at 17.44 MPa and average hardness was at 87.67 HV with the bonding time of 120 min and temperature at 540 °C. Statistically, the coefficient of determination analysis of bonding strength data was at 99.1%