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

直接观察异种摩擦焊接接头界面处的层生长 - 异种接头可靠性建模 -

基本信息

批准号：
10650700
负责人：
FUJI Akiyoshi
金额：
$ 2.3万
依托单位：
Kitami Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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.

众所周知，不同的摩擦连接工艺改变了紧靠结合线的材料的冶金性能和力学性能。本文对纯Ti/纯Al异种摩擦焊缝的连接过程进行了澄清，并利用高温光学显微镜对接头界面处经焊后热处理后的层生长进行了直接观察。(1)连接过程：无论接头直径如何，连接区域几乎是从接头中心轴线或半半径位置开始到焊缝周边。这种现象不同于同类摩擦焊缝。(2)层生长：a)在长时间加热后，PWHT在节理界面处饱和至约100 μm的中间层（金属间化合物相）宽度与节理界面位置无关。它由Al γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ γ。裂纹发生在Al钛合金与Al基体的界面处。b)外围区层生长速度快于中心轴区。c)中心轴区、半半径区和外围区相形成活化能分别约为93.2、96.1和77.0kJ/mol。其原因是由于摩擦焊接过程中产生的边缘区中间层宽度远大于中心区。因此，外围Ti和Al衬底之间的相互扩散比中心区域更容易。d)随着摩擦时间从2s增加到5s，活化能差值减小。这一原因被认为是由于长摩擦时间产生足够的热量而使相生长速度差最小。