increases with impact velocity. It is conjectured that the deformation initiates a micro-crack in the layer and the increasing of the impact velocity causes the length of the crack to increase. The X-ray image analyses of the fracture surface at the point with the maximum bonding strength in the compound layer after the tension test are shown in Fig. 9 (a) and (b). The impact velocities are 233 m/s and 260 m/s, respectively. Since the white dots show aluminum, a decrease of aluminum is observed with impact velocity. The decrease of aluminum indicates that the fracture surface moves from the aluminum side to the compound layer side with increasing impact velocity. Finally, when impact welding of a tube was carried out with impact velocities of 220 ~ 240 m/s, the bonding strength was stronger than the fracture strength of aluminum. CONCLUSIONS An aluminum tube was impact welded onto a stainless steel target and the following results were obtained. 1) Acceptable impact-welding was obtained at impact velocities from 200 m/s to 300 m/s because the inside flow of metal in the tube caused poor welding at impact velocities of 300 m/s or more. 2) Since the temperature generated at the impact face of the tube was lower than that obtained by the impact-welding of the bar, the thickness of the compound layer was thinner than that of the bar and hardly depends on impact velocity. 3) The bonding strength decreased with impact velocity because the bonding surface received shearing deformation with impact velocity. 4) The bonding strength was stronger than the fracture strength of aluminum, when impact welding of a tube was carried out at impact velocities of 230 ~ 250 m/s. References [1] Date H., S. Kobayakawa and M. Naka (1999) “ Microstructure and bonding strength of impact-welded aluminum-stainless steel joints”, J. Mater. Process. Technology, 55, 166-170. [2] Date H. (1998) ” Dynamic Behaviors of Aluminum Tube Subjected to a Longitudinal Impact and Tentative Impact Welding of a Tube”, Trans. of JSME, 64, 1316-1321. [3] Date H. and M. Naka (2000) ” Formation Mechanism of Compound layer by Impact Welding”, Proc. of PLASTICITY ’00, edited by A.S. Khan, H. Zhang and Y. Yuan, 219-221
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