Original paper(Vol.47 No.1 pp.39)

Impact welding of aluminum to stainless steel
- effect of surface roughness on joint and examination of formation process of compound layer -

Date Hidefumi; Kobayakawa Shin; Naka Masaaki

Abstract:An aluminum projectile was impact welded on a stainless steel target using a nitrogen gag gun at impact velocity over 250 m/s. The effect of surface roughness at the impact face of the target on the bonding area was examined using scanning acoustic tomography, and the strength of the bonding area was evaluated by a tension test. The microstructure and element distribution in aluminum/stainless steel joint were analyzed by means of a scanning electron microscope and energy dispersive X-ray spectroscopy (EDX). The experimental results of the concentrations of elements in the compound layer at the interface were compared with those obtained by a simple theoretical analysis.
The following results were obtained. The bonding area of the joints increased with the decrease of surface roughness. However, the increment of the bonding area due to the decrease of surface roughness hardly influenced the bonding strength. The thickness of the compound layer increased with impact velocity. In addition, the area of uniformly distributed elements in the layer extended with the increase in thickness of the layer. The concentrations of elements measured in the layer using EDX hardly varied with the impact velocity and were close to those of the theoretical results in which an equivalent was generated at the impact faces of a projectile and a target.

Key Words:impact-welding, surface roughness, interface, concentration, bonding strength