The present investigation attempts to understand the friction welding characteristics of sintered P/M steel preforms-wrought copper dissimilar parts. In order to achieve sound weld between these two materials the process parameters were optimized and inferred that the preforms of lower densities with lower process parameters yields quality weldments, established through post-weld tests. This study also envisages the influence of process parameters which include resident preform densities, friction pressure, upset pressure, and burn-off length on microstructure and mechanical properties of the welds. This work consolidates information on the aspects of joining P/M component with wrought materials for practical execution. © 2006 Elsevier B.V. All rights reserved.

K. Jayabharath

P. Venugopal

D. R.Gopalakrishna Achar

Copper

DISSIMILAR METALS

Friction welding

Metallographic microstructure

Preforming

POST-WELD TESTS

WROUGHT COPPER

STEEL POWDER METALLURGY

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Materials Science and Engineering A

The joining of copper to aluminum is inevitable for certain application in the electrical industry due to good conductivity and response offered by copper, aluminum for weight reduction. Whilst in the majority of cases, aluminum and copper can be joined by adhesive bonding, mechanical fastening, fusion welding and solid-phase welding techniques. Friction welding is well known for its ability to weld aluminum to many metals and consequently is being considered seriously. The present study describes about producing a sound joint between two dissimilar metals of pre-strained aluminum to commercially pure copper. Commercial pure aluminum is strained to reduce the disparity in strength level and the effect of pre-strain on friction welding is envisaged. The stronger metal (copper) in this combination is further weakened by intentionally removing some of the material so that a sound joint is obtained. Friction welding was carried out with pre-determined process parameters and the effect of initial geometry on friction welding is illustrated. Post weld characterization such as mechanical and microstructural studies of these welds was carried out to assess the quality of welds. © 2009 IEEE.

2009 2nd International Conference on Emerging Trends in Engineering and Technology, ICETET 2009

Influence of rubbing profile on friction welding of pre-strained aluminum to copper

Continuous drive friction welding studies on sintered powder metallurgical (P/M) steel preforms-wrought mild steel combination are reported in the present study. The work is a preliminary study to optimise the friction welding parameters and data generated by the present work is expected to contribute to friction welding of dissimilar and similar sintered P/M preforms to wrought metals or sintered P/M preforms - a planned future research work. Sound welds were obtained with all welding parameter combinations studied. The mechanical properties of welds were comparable to those of sintered P/M steel. Sintered P/M preforms deformed to a greater extent than wrought mild steel due to their low flow stress and thermal conductivity. The sintered density and other properties of the P/M preforms were found to dictate the deformation at the interface and consequently the weld strength. The results indicate that the current approach can be extended to other combinations of sintered P/M preforms. © 2006 Institute of Materials, Minerals and Mining.

Science and Technology of Welding and Joining

Preliminary studies on friction welding of sintered P/M steel preforms to wrought mild steel

Pulsing of the welding current is one approach for refining the fusion zone microstructure in materials joined by fusion welding. The effect of current pulse frequency on weld bead microstructure, tensile strength, and hardness in joining of powder metallurgical steel preform sheets to wrought copper was studied. Considering weld strength as the quality characteristic in the selection of process parameters, the Taguchi method is used to analyse the effect of each process parameter individually and of their interaction on weld strength, and subsequently to determine the process parameters leading to optimum weld strength. The application of pulsed current causes iron dendrites to become more equiaxed and uniformly distributed owing to dendrite fragmentation. Further, there was an optimum frequency range over which the microstructural refinement was maximal. The same optimum frequency range corresponded to maximum tensile strength. Enhanced fluid flow and reduced thermal gradients are thought to be responsible for refining the solidification structure and the resulting stronger welds. © 2004 institute of materials, minerals and mining.

Effect of pulse frequency in gas tungsten arc welding of powder metallurgical preforms

The present paper reports the feasibility studies on joining low density steel powder metallurgical (PM) preforms with wrought copper. In joining of these materials by tungsten inert gas (TIG) welding, the welding current, pulse frequency and the density of the PM preforms were found to have a strong influence in controlling the weld strength. When welded with lower welding currents (continuous current), copper infiltrated into the PM steel and with higher currents, thermal effects dominated in controlling the weld strength. Through the application of a pulsed current, grains became more equiaxed due to dendrite fragmentation. Microstructural refinement was found to be at a maximum at an optimum pulse frequency, which resulted in maximum tensile strength. © 2004 Institute of Materials, Minerals and Mining.

Powder Metallurgy

Fusion welding of steel powder metallurgical preforms to wrought copper

Metal composite materials are heterogeneous materials consisting of two or more different components bonded together internally. Special kinds of metal composites are produced by simultaneous plastic deformation of different metals. Process variables and characteristics of materials deformed simultaneously have an effect on the amount of deformation in each material, plastic zone, influencing the results of simultaneous plastic deformation. The present paper investigates the ability of dissimilar powder metallurgical (P/M) preforms to undergo simultaneous deformation using a special laboratory test. The influence of density ratio, thickness or volume ratio, type of deformation and total plastic strain on the strain experienced by individual metals are studied to establish the conditions of sound flow during simultaneous deformation. The results indicate that the simultaneous plastic deformation of dissimilar P/M preforms with different properties makes the deformation heterogeneous. The difference in the plastic strain experienced by each material increases with increase in the total plastic strain, volume or thickness ratio and deviation from the unit density ratio. The consolidation and metal matrix hardening mechanisms associated with the P/M preform deformation, strongly affect the deformation behavior of each metal and the onset of steady state deformation, during simultaneous deformation. Parameters such as volume ratio and type of deformation also strongly influence the simultaneous deformation results. © 2004 Elsevier B.V. All rights reserved.

Powder Technology

Analysis of deformation during simultaneous plastic deformation of dissimilar powder metallurgical preforms

Mathematical expressions have been derived for relating the values of apparent strength coefficient Ka (in N/mm2) and strain hardening exponent na to preform density ρ{variant}0, based on axial ring compression tests. These equations are consulted for prediction of cold hooker extrusion forces for P/M preforms of various starting preform densities, ρ{variant}0. Experimental values of extrusion forces are compared with those predicted. Such analysis demonstrates the usefulness of the generated Ka, na against ρ{variant}0 equations to avoid elaborate experimentation on the extrusion. Besides, the analysis suggests that the void closure is persistent till the theoretical density and if corrections are applied for force, theory and experiment agree well. © 1988.

Journal	Materials Science and Engineering A
ISSN	09215093
Open Access	No