Effects of Rotation Speed on Microstructure and Mechanical Properties in Ti/Cu Dissimilar Friction Stir Welding

The dissimilar welding of titanium and copper by fusion welding is very difficult because the melting points of the materials are very highly different and strong brittle intermetallic compounds (IMCs) can be easily produced in welded zone and heat-affected zone, etc. Friction stir welding was employed as a type of solid-state welding for Ti/Cu dissimilar welding to obtain a sound welded zone and reduce the total process cost. This study investigated how the metal flow of the welded zone changes according to the variation in the rotational speed of the tool, from 450 rpm to 600 rpm. When the rotational speed was too high, the plastic flow of the softened material increased and intermetallic compounds such as TiCu, Ti2Cu3, and Ti2Cu, were generated in the Cu region of the welded zone. The microstructural evolution of AS (Advancing Side) and RS (Retreating Side) were investigated and the soundness of the welded zone and its mechanical properties were evaluated through the microstructural evolution. A high hardness value of 200 Hv or more was exhibited in some points, due to the formation of intermetallic compounds in the RS (Cu) region. Ti/Cu dissimilar friction stir welding at a welding speed of 50 mm/min and an appropriate rotation speed of 500 rpm showed a good welded zone and mechanical properties.

Submerged Dissimilar Friction Stir Welding of AA6061 and AA7075 Aluminum Alloys: Microstructure Characterization and Mechanical Property

The possibility of underwater dissimilar friction stir welding of AA6061 and AA7075 aluminum alloy was explored to overcome the problem of hardness loss in different microstructural zones. Optical microscopy and electron backscattered diffraction were employed to characterize the microstructure of the joint. Vickers hardness measurements were conducted on the cross-section of the joint to evaluate the mechanical strengths. The results showed that the microstructure of the AA7075 side had undergone the same mechanisms as those occurring during conventional friction stir welding. In the case of the AA6061 side, in addition to typical restoration mechanisms, the grain subdivision was observed. The AA7075 side had finer grains compared to the AA6061 side, which may be related to the different morphology and size of precipitates. Moreover, friction stir welding caused a reduction in the hardness values in all the microstructural areas compared to those of corresponding base materials. For example, it caused a reduction in the hardness of a thermomechanically affected zone from 105 HV to 93 HV in the AA6061 side, and from 187 HV to 172 HV in the AA7075 side. The underwater media improved the overall hardness values in thermo-mechanically affected zones (13% reduction in hardness) compared to those reported in literature (57% reduction in hardness).

Investigation of microstructural and mechanical properties of AA1050-AZ91D dissimilar friction stir welding

Joining of aluminium and magnesium alloys frequently pose significant challenges to the extent where joining may seem impossible, due to differences in the physical, metallurgical, and chemical properties of the materials. Friction stir welding is a solid-state welding technique which uses a non-consumable tool to join metals. This study examines the dissimilar friction stir welding of 3 mm thick AA1050 and AZ91D alloy sheets. Successful defect-free joints were achieved at rotational speeds of 400 rpm and 600 rpm, and a constant traverse speed of 50 mm/min. The metallurgical investigations used to characterize the microstructure of the welds are optical microscopy (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The microstructures of the samples show distinct morphology attributed to their different rotational speeds. However, Al3Mg2 intermetallics (IMCs) phase was detected in the white bands present in both weld samples. The IMCs were formed through solid-state diffusion. The mechanical properties characterizations includes the microhardness profiles and tensile testing. The variation in the rotational speeds do not have a significant effect on the microhardness distribution of the weld samples. The tensile strength of the dissimilar weld improved substantially with the presence of an interpenetration feature (IPF).

Parameters Optimization of Dissimilar Friction Stir Welding for AA7079 and AA8050 through RSM

Aluminium alloy is widely used in engineering application, and it can be classified based on the constituent elements or alloying elements. Aluminium alloy is preferred for the nature of its tensile strength, ductility, and corrosion resistance in this research to make a dissimilar friction stir welding joint of aluminium alloys 7079 and 8050 materials. The tensile strength of the weld joint is estimated by the influence of the response surface methodology approach. The welding is carried out by preferred process parameters with a tool speed of 1000–2500 rpm, tool pin diameter of 2–6 mm, welding speed of 50–300 mm/min, and tool shoulder diameter of 10–20 mm. The ANOVA analysis and the prediction of tensile strength were conducted efficiently. From the RSM analysis, the tool pin diameter mostly modified the output of the result.