Direct observation of layer growth at interface of dissimilar friction weld joints - Modeling of reliability for dissimilar joint -

点击翻译按钮获取中文摘要

It is well-known that the dissimilar friction joining process alters the metallurgical and mechanical properties of material immediately adjacent to the bondline. The present paper examines the the joining process of pure Ti/pure Al dissimilar friction weld was clarified, and the layer growing by post-weld heat treatment (PWHT) at interface of the joint was carried out by direct observation with a high temperature optical microscope.(1) Joining process : The joining area almost started from joint center axis or half radius location to periphery of weld joint in spite of joint diameter. This phenomena was different from that of similar friction weld joints.(2) Layer growing :a) The width of intermediate layer (intermetallic compound phase) that occurs at the joint interface by PWHT saturated up to approximately 100 μm after long time heating in spite of location of joint interface. It was consisted with AlィイD23ィエD2Ti, and grew mainly from Al substrate to Ti one. The crack occurred at the interface of AlィイD23ィエD2Ti and Al substrate.b) Layer growing at periphery region was faster than that at center axis region.c) The activation energies of phase formation at center axis, half a radius and periphery regions were approximately 93.2, 96.1 and 77.0kJ/mol, respectively. This reason was thought as follow : the width of the intermediate layer at periphery region produced during friction welding was much wider than that of center region. Therefore, the mutual diffusion between Ti and Al substrates at periphery was easier than at center region.d) The difference of activation energy was decreased when friction time increased from 2s to 5s. This reason is thought that the difference of phase growing speed was minimized because heat generation reached enough by long friction time.