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Cold metal transfer (CMT) welding is a promising process to improve the mechanical characteristics of the hard to weld 7075-T6 aluminium alloy owing to its unique advantages in contrast to conventional metal inert gas welding process. The welded joints, using ER5356, were identified and characterised by means of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Mechanical properties were measured by tensile and hardness tests. Results indicate that CMT provides better joint tensile strength and ductility compared to metal inert gas welding. The softness in the heat affected zone was very low, but a big hardness gap was recognised in the welded metal compared to base metal. The joint had mechanical property coefficients of 77%, 60% and 69% for yield strength, ultimate tensile strength and elongation respectively.

The lap joint of a commercially pure titanium plate (CP Ti) to a low-carbon steel plate was produced with a vacuum-brazed furnace using a silver-based filler alloy at different temperatures and lap widths in order to investigate the effects of such brazing parameters on the joint strength and structure. It was found that the shear strength of brazed joints depends strongly on the lap width. Furthermore, we have discovered that the shear strength of the joints increases as the lap width decreases. The maximum shear strength of the joints, 54 MPa, was obtained when they were brazed at 850°C for 15 minutes. Our observations indicate that intermetallic compound layers of CuTi and Cu 2 Ti were formed at the interface of the brazed area. An increase in the brazing temperature led to increased growth of these layers. Shear tests show that the fracture path occurred mainly at the CuTi layer, because this layer is hard and brittle.

Table 1 Chemical composition of the aluminum base metal 1100H24 (mass %). retracted while the tool continued to turn.The surface for the observation of microstructure was etched by 3% Nital to reveal the steel microstructure and subsequently by 1% HF aqueous solution to reveal the aluminum microstructure.The microstructure was observed with an optical microscope and SEM (Scanning Electron Microscope) for closer observations. A peel test was employed to estimate the fracture load of the obtained joint. The schematic view of the specimen for the peel test is shown in Fig. 4.Temperature measurements at positions close to the zinccoated steel surface (0.3 mm down from the surface) were carried out by using a thermocouple (K-type) percussion-welded to the bottom of holes drilled from the back surface of the steel specimen. X-ray diffraction analyses were carried out to identify phases present on the fracture surfaces of joint after peel tests.

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