1989 Volume 7 Issue 4 Pages 444-449
Copper-tungsten sintered alloys (Cu-W) containing 70, 80, 90 and 100 (pure tungsten) mass%W have been friction-welded to oxygen free copper (OFC), in order to investigate the effect of the W content on bond strength. The tensile strength of joints obtained decreased with the increase in W content. In the joints of Cu-90%W to OFC, a layer which consisted of W grains elongated in a direction parallel to the weld interface was observed in the Cu-W adjacent to the weld interface. A similar layer, including many microcracks, was also observed in the joint of pure W to OFC. Since the layer consisting of elongated grains was also observed on the faying surface, the formation of this layer was attributed to plastic deformation introduced by machining (turning, grinding) of the faying surface. The joint with this layer was fractured in the Cu-W or pure W adjacent to the weld interface as well as the weld interface. However, when this layer was removed by polishing on metallographic paper, joint was not fractured in the Cu-W or pure W. These results suggest that the layer was embrittled. In contrast to this, for W content less than 80%W, the layer with elongated grains was not observed at weld, and the joint was fractured at weld interface and/or in the OFC. In this case, since a lot of W particles were found to be picked up in the OFC adjacent to the weld interface, the surface layer with elongated grains was presumably removed during friction welding.
