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采用扫描电镜、能谱分析、透射电镜、X射线衍射和电子衍射等分析手段,研究了Cu含量对Sn-Ag-Cu/Cu钎焊接头界面处生成的金属间化合物Cu6Sn5的生长形态对接头剪切强度的影响。结果表明:在Sn-Ag-Cu钎焊接头的界面处有扇贝状的Cu6Sn5金属间化合物的生成,调整Cu含量,可改变Cu6Sn5的形状和避免大柱状的Cu6Sn5生成,提高接头剪切强度,钎焊接头的断裂主要是韧性断裂。时效试验结果表明:当时效温度为室温、时间为1000 h时,Cu含量高的Sn-Ag-Cu钎料所生成Cu6Sn5的形态变化为长的空心截面六边形柱体,由于Cu6Sn5所形成的空心孔洞导致Sn-Ag-Cu/Cu界面成为强度弱区,从而使接头的剪切强度有所下降。 相似文献
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By means of the quadratic regression combination design process, the regression equations of nugget diameter and tensile shear load of spot welded joint were established. Effects of welding parameters on the nugget diameter and the tensile shear load were investigated. The results show that effect of welding current on nugget diameter is the most evident. And higher welding current will result in bigger nugget diameter. Besides, interaction effect of electrode force and welding current on tensile shear load is the most evident compared with others. The optimum welding parameters corresponding to the maximum of tensile shear load have been obtained by programming using Matlab software, which is 4, 7 kN electrode force, 28 kA welding current and 4 cycle welding time. Under the condition of the optimum welding parameters, the joint having no visible defects can be obtained, nugget diameter and tensile shear load being 6. 8 mm and 3 256 N, respectively. 相似文献
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CORBA通过可移植拦截器(Portable Interceptor)为用户提供了一种监视并控制ORB内部运行的方法。论文论述了OMG/CORBA规范中的可移植拦截器机制,并阐述采用拦截器机制实现分布式对象安全控制的方法。文中还给出了具体应用实例。 相似文献
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基于通识教育的芝加哥大学计算机专业培养模式 总被引:1,自引:1,他引:0
受国家留学基金委的派遣,笔者曾于2005与2006年间在美国芝加哥大学/Argonne国家实验室做了为期一年的访问学者。期间师从网格之父Ian Foster教授,进行网格安全研究;同时对芝大计算机专业的教学进行了调研,全程旁听了两门核心课程,还对其他四门课程进行了部分旁听,并参加了校园内的多项学术活动。本文结合笔者在芝大的亲身经历和真实感受, 相似文献
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