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【答案】应助回帖
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zoe122208: 金币+120, 翻译EPI+1, ★★★★★最佳答案 2013-11-22 20:22:48
Tension tests are performed on welding joints for different thickness of inner tubes and the two results are either break-up of the joints or fracture of the parent metal. When thickness of the inner tube is less than the critical value, the tension test will result in joints breaking up at which the tensional strength of the joint is smaller than that of the parent aluminum alloy. This is because when thickness of the inner tube is less than the critical value, the high speed impact by the outer tube will cause the inner tube to deform and become unstable, i.e., welding does not get effective due to the gap between inner and outer tubes. When thickness of the inner tube reaches the critical value, the test results in fracture of parent metal. This shows that the tensional strength of the joint is greater than that of the parent aluminum alloy, hence an effective welding.
With the gradual increase in thickness of the inner tube, the welded area of the joint increases, too and when thickness of the inner tube reaches the critical value, the weld sample can hardly completed stripped off. From SEM analysis of the joint on the stripped sample, it is found that when thickness of the inner tube has not yet reached the critical value, no impact and transition zone is formed between the inner and outer tubes; while when thickness of the inner tube reaches the critical value, a transition zone appears at the connection between the two types of metals. By line scanning analysis of this transition zone, it is seen that the maximum width of the transition zone reaches 40μm. In a wide range around the middle of this zone, proportions of Al and Fe elements remain basically unchanged. The Al element content is slightly higher and at either side of the transition zone, the elements' content at their dual side quickly decreases, which shows when the critical thickness is reached, the welding joint is uniform.
注：第二句中文里“此时接头抗拉强度大于铝合金母材的抗拉强度”应该是小于吧？不然逻辑上说不通，请检查。我是按小于译的。
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