EFFECT OF MICROSTRUCTURE ON MECHANICAL PROPERTIES OF FRICTION- WELDED JOINTS BETWEEN ALUMINUM ALLOYS (6061, 5052) AND 304 STAINLESS STEEL

摘要

Commercial Aluminum alloys 5052 and 6061 were welded to AISI 304 stainless steel using a continuous drive friction welding technique. In order to study the effect of interlayer on the joining efficiency, Cu interlayer was diffusion bonded to stainless steel and subsequently friction welded to Al alloys. The microstructure, microtexture and mechanical properties were investigated and process parameters were optimized. The reaction layer essentially consisted of FeAl intermetallics and this layer formed with 2 μm thickness under the condition of relatively long friction time (t1) and low upset pressure (P2). The interface between Al alloy/ stainless steel 304 was very sharp for direct friction welded specimens and the interfaces at stainless steel 304/Cu and Cu/Al alloy for specimens welded with Cu interlayer were diffuse in nature. Orientation imaging microscopy results for direct friction welded specimen showed that the average grain size of Al close to the interface was around 100 urn and the extent of isorientations at the interface was found to be maximum. The paper presents the details of the microstructure evolved at the interface during friction welding and also attempts to correlate with the observed mechanical properties.