The cross-sections of specimens bonded at the impact velocities of 238 m/s and 339 m/s are shown in Fig. 3(a) and (b). The contour of the outer wall after deformation is similar to the mushrooming profile. However, the profile of the inner wall is complicated as described below. Though the velocity of the metal flowing toward the center of the tube decrease as the inside of the tube is filled with the metal, the metal of the outer wall has continued to flow out during impact. The velocity difference of the two metal flows caused a crack to be initiated, grow and penetrate the wall. Finally the inside metal only is bonded at the target and the other part of the tube is separated from the target. It is clarified from Fig. 3 (a) and (b) that the outer ring area shown in Fig.1 (a) has vanished at a high velocity impact because the outer edge of the impact face of the projectile was lifted up from the target surface and the outer ring area was torn up. The effect of the impact velocity on the bonded area is given in Fig. 4. The size of the area hardly increases with impact velocity unlike the bar [1]. This means that the heat generation on the impact face of the tube is almost constant regardless of impact velocity. (a) v = 238 m/s (b) v = 339 m/s Fig. 3 Deformation process of projectile 300 280 260 240 220 0 50 100 150 Impact velocity V m/s Bonded area A mm2 Fig. 4 Effect of impact velocity on bonded area COMPOUND LAYER AND ELEMENT DISTRIBUTION The magnified microstructure and X-ray image analysis of elements can be seen in Fig. 5 (a) and (b). Table I gives quantitative analysis of the phase formed at the joining interface in Fig. 5 (a). The maximum thickness of the compound layer was about 8 µm as seen in Fig. 5 (a) and (b). Figure 6 shows the maximum thickness of the compound layer plotted against impact velocities. The thickness hardly increases with impact velocity. The element distribution hardly depends on the position in the compound layer as shown in Table I and the content is almost constant regardless of impact velocity as shown in Fig. 7. The content of aluminum is more than that of Al3Fe seen in the alloy phase diagram. The lack of dependence of aluminum content on the impact velocity and the position in the layer described above is the same as th
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