Effect of grain size on hot cracking resistance of the HAZ metal of welded joints in creep-resisting alloys

Summary

Al₂O₃/6061 aluminium alloy composite was welded to aluminium alloys (6061‐T6, 5052‐H14, 2017‐T4) using an inertia type friction welding machine to investigate the microstructures and hardness distributions of friction welded joints. Regardless of the aluminium alloys used, finer alumina particles and finer grain structures were observed in the area near the weld interface. And the occurrence of mechanical mixing and moving of alumina particles into a region other than the composite were observed clearly on the weld interface. The distance moved by the alumina particles became greater in the order of the alloys, 6061, 5052 and 2017. A softened area was observed in the heat affected zone of all the aluminium alloys. It was found 30 days after welding that the hardness of the welded joint between the composite alloy and 6061 alloy had not changed significantly, whilst that of the welded joint between the composite alloy and 2017 was observed to have recovered to the previous standard 14 days after welding.