Over the 2010s technological improvements allowed metal additive manufacturing to graduate from a prototyping tool to a widespread, full-scale manufacturing process. Among the capabilities still un...

Advances in additive manufacturing of metal-based functionally graded materials

Introduction Electron beam welding is a fusion welding process and can be used for welding a wide variety of metals, such as stainless steel, Inconel, copper and other variations of their grades. The metal thicknesses range from foils to thick metals sheets. In addition, two different metals or alloys can be welded together. E-beam welding has a vast variety of applications such as; electronics and packaging, automotive and aircraft industry, and in medical technology. In particular, down-hole tools for the oil and gas industry can be processed.

Electron Beam Welding

Effect of a Zn interlayer on dissimilar FSSW of Al and Cu

Similar and dissimilar material joints of AISI grade 304 (1.4301) and AISI grade 316 (1.4401) austenitic stainless steel by solid state diffusion bonding and transient liquid phase (TLP) bonding are of interest to academia and industry alike. Appropriate bonding parameters (bonding temperature, bonding time, and bonding pressure) as well as suitable surface treatments, bonding atmosphere (usually high vacuum or protective gas) and interlayers are paramount for successful bonding. The three main parameters (temperature, time, and pressure) are interconnected in a strong non-linear way making experimental data important. This work reviews the three main parameters used for solid state diffusion bonding, TLP bonding and to a smaller degree hot isostatic pressing (HIP) of AISI grade 304 and AISI grade 316 austenitic stainless steel to the aforementioned materials (similar joints) as well as other materials, namely commercially pure titanium, Ti-6A-4V, copper, zircaloy and other non-ferrous metals and ceramic materials (dissimilar joints).

Diffusion Bonding and Transient Liquid Phase (TLP) Bonding of Type 304 and 316 Austenitic Stainless Steel—A Review of Similar and Dissimilar Material Joints

There has been uncertainty about the best pin position for friction stir lap welding (FSLW) of Al-to-Ti so that weld samples can achieve the highest attainable load during tensile-shear testing. In this study, tests were conducted to evaluate how much tensile-shear load an Al6060 to Ti–6Al–4V (6060-Ti64) FSLW sample of a set width (Fm/ws) can support before fracture depends on the pin positioning related microstructures in the weld interface region. Microstructures differ depending on whether or not the tool pin penetrates the lapping interface. It has been found that Fm/ws values of the present macro-defect free weld samples vary quite significantly but in general are significantly higher than those reported in the literature. When the penetration depth is zero a thin Al6060–Ti64 interface layer forms and this layer does not grow beyond 250 nm. It will be shown that the thin interfacial layer can support a high tensile-shear load and thus the adjacent Al6060 material shears to fracture. When the pin penetrates during FSLW and thus the commonly observed mix stir zone (MSZ) forms, values of Fm/ws are lower than that of zero pin penetration welds but remain quite high. This can be explained by cracks needing to propagate through the tough and high strength α(Ti) regions in MSZ, requiring a high load to cause fracture.

Microstructures in interface region and mechanical behaviours of friction stir lap Al6060 to Ti–6Al–4V welds

The welding of dissimilar materials finds a wide variety of applications in the fields of industrial construction and manufacturing, where the characteristic features of the different materials are optimized for the desired application to result in cost effectiveness and value addition. Non-fusion welding methods such as solid state welding and high energy beam welding are more popular for welding dissimilar metal combinations, due to fewer complications, than fusion welding, which melts the base metal and forms brittle intermetallic compounds (IMCs) that may lead to failure. Various factors have to be considered when assessing the feasibility of welding dissimilar metals and producing a sound weld joint. This paper presents a broad classification of the most commonly used welding processes for dissimilar materials, discusses some of the commonly used welding processes with examples of some common material combinations, critical factors for good welding, and practical difficulties arising from the physical and chemical properties of materials. From the findings, it can be inferred that continuous improvement and research is still required in the field of dissimilar metal welding, particularly in the light of increasing demand for tailored material for modern engineering and industrial applications.

Madan Shrestha

Papers

Trends in Joining Dissimilar Metals by Welding