Superplastic Forming and Reaction Diffusion Bonding Process of Hollow Structural Component for Mg-Gd-Y-Zn-Zr Rare Earth Magnesium Alloy

This work fabricated a double hollow structural component of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy by superplastic forming (SPF) and reaction-diffusion bonding (RDB). The superplastic characteristic and mechanical properties of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy sheets at 250–450 °C were studied. Tensile tests showed that the maximum elongation of tensile specimens was about 1276.3% at 400 °C under a strain rate of 1 × 10−3 s−1. Besides, the effect of bonding temperature and interface roughness on microstructure and mechanical properties of the reaction diffusion-bonded joints with a Cu interlayer was investigated. With the increase of temperature, the diffusion coefficient of Cu increases, and the diffusion transition region becomes wider, leading to tightening bonding of the joint. However, the bonding quality of the joint will deteriorate due to grain size growth at higher temperatures. Shear tests showed that the highest strength of the joints was 152 MPa (joint efficiency = 98.7%), which was performed at 460 °C.

Diffusion Bonding of Ti6Al4V at Low Temperature via SMAT

Titanium alloys used to be welded to gain good joint strength at 920 °C through diffusion bonding. However, due to the heat preservation at high temperatures for a long time, we obtain joints with great bond strength while the mechanical properties of the sheet are lost. In this paper, taking Ti6Al4V alloy as an example, we studied the microstructure of the surface under the different times of surface mechanical attrition treatment (SMAT). In addition, the microstructure and mechanical properties after diffusion bonding at 800 °C-5 MPa-1 h were also conducted. The results show that the shear strength of TC4 alloy welded joint after SMAT treatment is improved, and the maximum shear strength can reach 797.7 MPa, up about 32.4%

Solide State Diffusion Bonding of Al6061-SiC Nanocomposites

Aluminium matrix composites are both strong and lightweight, and are limited in their applications due to the proper choice of welding process. Conventional welding that is based on fusion at the welded joint is not suitable because it leads to the formation of certain defects at the welded joint. For this reason, solid-state welding such as diffusion bonding is one of the suitable joining methods, as there will be no melting of any of the constituents. The solid-state diffusion bonding at 520° C of Al6061-SiC nanocomposites was investigated. This composite material was made by powder metallurgy, where aluminium alloy Al6061 was selected as the base metal, and SiC nanoparticles with an average size of 50 nm were added as reinforced particles. The effects of bonding time on the microstructures and mechanical properties of the welded material were investigated. The main characterisation techniques were optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, x-ray diffraction, and microhardness measurements. We have found that increasing the holding time up to 3 h at 520° C strengthens the weldability of the two basic composite materials and increases their hardness. X-ray diffraction analysis did not reveal any new phase during diffusion welding; it is considered one of the advantages of using the solid-state diffusion welding technique for the assembly of this kind of composite material. The welding success of this composite material widens its field of use, such as the automotive or space industry, because it is a light material with high mechanical properties.