Quantitative characterization of lamellarαprecipitation behavior of IMI834 Ti-alloy in isothermal and non-isothermal heat treatments  

IMI834钛合金等温和非等温热处理过程中片层α相析出行为的定量表征

作　　者：Xue-yan LIU Hong-wei LI Mei ZHAN Hong-rui ZHANG 刘雪艳;李宏伟;詹梅;张洪瑞(西北工业大学材料科学与工程学院,凝固技术国家重点实验室,西安710072;西北工业大学,陕西省高性能精确成形技术与装备重点实验室,西安710072)

机构地区：[1]State Key Laboratory of Solidification Processing,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China [2]Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment,Northwestern Polytechnical University,Xi’an 710072,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第1期162-174,共13页中国有色金属学报（英文版）

基　　金：financial supports from the National Natural Science Foundation of China(No.51675433);the Natural Science Foundation for Distinguished Young Scholars of Shaanxi Province,China(No.2019JC-09)。

摘　　要：To reveal the affecting mechanism of cooling rate on lamellarαprecipitation,the precipitation behaviors of lamellarαphase in IMI834 titanium alloy during isothermal and non-isothermal heat treatments were quantitatively characterized using experimental analysis.Critical precipitation temperatures at various cooling rates were obtained using thermal dilatation testing.Using metallographic microscopy,electron microprobe analysis,and data fitting methods,the quantitative evolution models of average width,volume fraction,and solute concentration in theαandβphases were built for different temperatures or cooling rates.A comparison between the two precipitation behaviors showed that the average width and volume fraction of lamellarαphase under non-isothermal conditions were smaller than those under isothermal conditions.With increasing cooling rate,the average width and volume fraction were decreased significantly,and the critical precipitation temperatures were reduced.This phenomenon is mainly attributed to the decreased diffusion velocity of solutes Al,Mo,and Nb with increasing cooling rate.为了揭示冷却速度对片层α相析出的影响机制,采用试验分析方法对IMI834钛合金在等温和非等温热处理过程中片层α相的析出行为进行定量表征。通过热膨胀试验获得不同冷却速度下片层α相的临界析出温度。基于金相显微镜和电子探针分析以及数据拟合方法,建立片层α相的平均宽度、体积分数以及α和β相内的溶质浓度随温度和冷却速度的定量演化模型。两种条件下的片层α相析出行为对比发现:非等温冷却过程中片层α相的平均宽度和体积分数均小于同温度下等温相变过程中片层α相的平均宽度和体积分数。随着冷却速度的增加,片层α相的宽度和体积分数显著减小,临界析出温度降低。发生上述现象的原因是溶质元素Al、Mo和Nb的扩散速度随冷却速度增加而减小。

关 键 词：heat treatment lamellarαphase precipitation morphology evolution critical precipitation temperature volume fraction model solute concentration evolution model 

分 类 号：TG166.5[金属学及工艺—热处理]