铸锭GH 3625合金微观偏析及均匀化热处理

为消除铸态GH 3625合金的显微偏析,改善其热加工性能,建立其均匀化动力学并制订均匀化处理制度,采用ImagePro Plus软件、扫描电镜(SEM)和能谱分析仪(EDS),对通过真空感应熔炼和电渣重熔双联工艺制备的GH 3625合金电渣锭的显微组织及元素偏析情况进行分析和研究.同时,对铸态GH 3625合金在不同温度下同一时间及同一温度下不同时间进行了均匀化处理.结果表明:GH 3625合金电渣锭存在明显的枝晶间微观偏析,主要偏析元素为Nb、Mo等,形成富Nb的Laves相、MC碳化物;不同元素的偏析程度为NbMoTiAlCr;Nb、Mo、Ti、Al在枝晶间大量富集,使得Laves等多种非平衡相在枝晶间析出;在均匀化过程中,随着均匀化温度的升高和时间的延长,偏析元素逐渐扩散均匀;当热处理制度为1 130℃×32 h时,元素偏析基本消除;Laves相体积分数随均匀化处理时间呈明显指数函数特征,V1 130℃=0.033 5exp(-0.163 1t).

Microsegregation and homogenization of GH 3625 alloy ingot

To eliminate the micro-segregation, improve the hot workability, and establish the uniform dynamics, and formulate the homogenization schedule of cast GH3625 alloy, microstructure and element segregation of as cast GH 3625 alloy after vacuum induction melting ( VIM) and electroslag remelting ( ESR) was studied by means of Image-Pro Plus, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Cast GH 3625 alloy was homogenized at different temperatures or different time. The results show that GH 3625 alloy exhibits dendritic segregation, in which Nb and Mo are mainly segregation elements, and they formed Nb-rich Laves phase and MC carbides. The elements displayed different segregation degree as the following sequence: Nb> Mo> Ti>Al>Cr. Nb, Mo, Ti, and Al are largely enrichedenriched in the inter-dendrite, resulting in the precipitation of Laves and other non-equilibrium phases . The elements diffused more evenly during homogenization, as the homogenization temperature increases or the time prolongs. The element segregation of the GH 3625 alloyalmost eliminated after homogenization treatment at 1130℃ for 32 h. Laves phase volume fraction and the homogenization time obey the following exponential function relation:V1130℃=0.0335exp(-0.1631t).