Interface characteristics and performance of magnetic pulse welded copper-Steel tubes

An attempt has been made to join two tubes of pure copper and low carbon steel by magnetic pulse welding in lap joint configuration. Satisfactory welds were obtained with an optimal set of parameters consisting of discharge energy, standoff distance and initial collision angle. The welded interface revealed a wavy morphology with pockets of intermixed metal vortices. High resolution electron microscopy and microanalysis showed the formation of nano-grains along the interface and evidence of short distance interatomic diffusion across the weld joint respectively. The strain hardening effect due to high energy impact led to significantly higher microhardness on the steel side of the interface. Torsion tests confirmed acceptable joint strength as failure took place in the copper base material. (C) 2017 Elsevier B.V. All rights reserved

Effect of weld parameters on joint quality in friction stir welding of Mg 2 alloy to DP steel dissimilar materials

Dissimilar material joining between magnesium (AZ31B) alloy and dual-phase steel (DP600) was achieved using the friction stir welding (FSW) process. The present work aimed at studying the effect of tool rotational speed and welding speed on the microstructure and mechanical properties of the dissimilar joints. The joints were fabricated at tool rotational speeds of 800 and 1600 rpm with weld speeds of 50, 100, and 150 mm/min, respectively. The plunge depth of 0.2 mm and tool tilt angle of 2° was kept constant during the welding. Temperature rise and variation of torque during the welding process were recorded. Optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy (EDS), and X-ray diffraction studies were carried out to understand the microstructural changes, the interface of the weld joints, fracture morphology, and formation of intermetallic compounds during FSW. Maximum joint efficiency of 76.4% was achieved with respect to AZ31B. The microstructural observation revealed the formation of finer grains at the stir zone for all weld parameters because of the dynamic recrystallization. The metallurgical bonding between the dissimilar materials was observed due to the formation of intermetallic compounds. The formation of the sawtooth profile at the joint interface indicated mechanical interlocking between AZ31B Mg alloy and DP600 steel. Though the AZ31B Mg–DP600 steel combination is highly immiscible, the present attempts have successfully created the joining, where one of the substrates provides lightweight while the other provides strength

Microstructure and properties of parts manufactured by directed energy deposition of water-atomized low-alloy steel powders

The feasibility of using water-atomized low-alloy steel powders Fe-0.11C-0.59Mn-0.43Si-0.45Cu-0.3Cr-0.45Ni0.15Mo-0.05 V (wt.%)] for additive manufacturing using a laser-based directed energy deposition (DED) process was evaluated. Different processing parameter combinations were assessed to arrive at optimum parameters to fabricate different sample geometries, which were characterized in terms of microstructures and mechanical properties. Selected samples were also evaluated after homogenization at 1075 ?C for 10 min. The results show that DED of water-atomized low-alloy steel powders is possible, yielding unique non-directional and refined microstructures with fine spherical oxide particles dispersed throughout the matrix. The maximum tensile strength and total elongation achieved in the as-built condition were 315 MPa and 3.4%, respectively, which improved to 350 MPa and 10.3% after heat treatment. The presence of a sizeable fraction of oxide nanoparticles, which presumably originated from the oxide layer of the water-atomized powder, enabled retention of microhardness/strength after heat treatment despite grain coarsening. However, the porosity and loss of C and Mn were found to be the major concerns with water-atomized powder. We believe that inconsistent powder flow due to the irregular morphology of the powders is the primary cause of the porosity. On the other hand, the high laser absorptivity of the powders due to their rough surface texture and surface oxides could be responsible for the loss of alloying elements due to excessive powder and/or melt pool temperatures. Although the results of our study are quite encouraging, powder characteristics like size and/or morphology need to be further optimized to exploit the full potential of this additive manufacturing methodology