塑性流動現象を利用したアルミニウム合金鋳物の表面改質

抄録

Aluminum alloy castings meet a requirement of lightweight vehicles and attract a lot of attention. However they suffer from some defects such as porosity, segregation and others. Fusion processes used to modify the surface locally, lead to secondary defects like porosity and cracking in modified zone. In this paper, a new surface modification process, which uses friction phenomenon, is suggested. It is named as Friction Thermomechanical Process (hereafter referred as FTMP). In this process, a non-consumable rod is forced while rotating, against the substrate surface. The friction heat, generated at the interface between the rod and substrate, makes the substrate metal to undergo plastic deformation. The coarse cast microstructure at the substrate surface is continuously refined due to dynamic recrystallization. As a result, FTMP process is suitable for surface modification of aluminum castings. Cast defects were found to be eliminated in the surface zone of 2 mm depth where large fiat surface region. Modified zone showed refined microstructure and improved hardness.