Ti-44Al-6Nb-2Fe合金低温超塑性及高温拉伸组织演化  

Low-temperature Superplasticity and High-temperature Tensile Microstructure Evolution of Ti-44Al-6Nb-2Fe Alloy

作　　者：董书琳 曲迎东[1] 陈瑞润[2] 郭景杰[2] 王琪 李广龙[1] 张伟[1] 于波 DONG Shulin;QU Yingdong;CHEN Ruirun;GUO Jingjie;WANG Qi;LI Guanglong;ZHANG Wei;YU Bo(School of Materials Science and Engineering,Shenyang University of Technology,Shenyang 110870,China;School of Materials Science and Engineering,Harbin Institute of Technology,Harbin 150001,China;State Key Laboratory of Light Alloy Casting Technology for High-end Equipment,Shenyang Research Institute of Foundry Co.,Ltd.,Shenyang 110027,China)

机构地区：[1]沈阳工业大学材料科学与工程学院,沈阳110870 [2]哈尔滨工业大学材料科学与工程学院,哈尔滨150001 [3]沈阳铸造研究所有限公司高端装备轻合金铸造技术国家重点实验室,沈阳110027

出　　处：《材料导报》2024年第1期171-176,共6页Materials Reports

基　　金：高端装备铸造技术全国重点实验室开放课题(CAT2023-008);辽宁省教育厅面上项目(LJKMZ20220464);辽宁省自然科学基金(2020-KF-14-03);高端装备轻合金铸造技术国家重点实验室项目(LACT-009)。

摘　　要：为改善高Nb TiAl基合金的热变形能力,本研究利用Fe部分替代高Nb TiAl基合金中的Nb,熔炼制备新型高Nb含Fe的Ti-44Al-6Nb-2Fe合金。首先对合金铸锭进行包套锻造,再对锻造合金在800~1 000℃、1×10^(-4)s^(-1)初始应变速率下进行高温拉伸实验,对合金的高温拉伸变形行为和组织演化行为进行研究。结果表明,合金中含有较多B2相,占30%~40%,随高温拉伸温度升高,合金动态再结晶作用增强,位错减少,晶粒尺寸增大,晶粒长径比降低,这些组织演化特征与合金的应力-应变状态和热变形能力提升相对应。合金在800℃和850℃拉伸变形时,B2相为硬脆相,B2相及B2/γ相界面处的应力集中导致该区域形成大量裂纹及孔洞(800℃时孔洞百分比为14.5%),延伸率较低(800℃时延伸率为123.1%),甚至发生提早断裂,试样断裂处颈缩现象明显;合金在900℃拉伸变形时,应变速率敏感指数m=0.284,延伸率明显提高(900℃时延伸率为163.0%),试样断裂处仍有颈缩现象;合金在950℃和1 000℃拉伸变形时,B2相转化为“软”相,发挥了很好的应力-应变协调作用,B2相与γ相之间发生了广泛的晶界滑动,组织中几乎无裂纹孔洞出现,延伸率陡然提高(950℃时延伸率为307.9%),试样断裂处无颈缩现象,合金具备超塑性,但该合金在TiAl基合金中属于低温超塑性。较高的B2相含量及其所发挥的优异的应力-应变协调作用是该合金具备低温超塑性的重要原因和特色之处。In order to improve the hot deformation processing capability of high-Nb TiAl based alloys,this study used the Fe element to partly replace the Nb element in high-Nb TiAl based alloys to prepare the new-type high-Nb and Fe-contained Ti-44Al-6Nb-2Fe alloy.The alloy ingot was firstly isothermally package forged,and then the high-temperature tensile testing was carried out on this forged alloy at the initial strain rate of 1×10^(-4) s^(-1) and temperatures of 800-1000℃,and the high-temperature tensile deformation behavior and microstructure evolution behavior of the alloy were studied.The results show that the alloy contains more B2 phases(30%-40%).With the increasing of temperature,the dynamic recrystallization effect increases,dislocation decreases,grain size increases,and aspect ratio of grains decreases,all of which correspond to the stress-strain state and enhancement of hot deformation processing capability of the alloy.When the tensile testing is at 800℃and 850℃,B2 phase is a brittle phase,and the stress concentration in the regions of B2 phase and B2/γphase interface leads to the formation of a large number of cracks and holes(14.5%cavity at 800℃),resulting in a low elongation(123.1%elongation at 800℃),even the early fracture,and the neck shrinkage is obvious.When the tensile testing is at 900℃,the strain-rate sensitive exponent m is 0.284,the elongation is significantly increased(163.0%),and the neck shrinkage still exists.When the tensile testing is at 950℃and 1000℃,B2 phase has transformed into a‘soft’phase that plays a good role in stress-strain coordination effect,and extensive grain boundary sliding between B2 phase andγphase can be found.There are almost no cracks and holes in the microstructure,and the elongation increases sharply(307.9%at 950℃)without neck shrinkage.The alloy has superplasticity at 950℃ and 1000℃,which belongs to low-temperature superplasticity for TiAl based alloys.The higher content of B2 phase and its excellent stress-strain coordination effect are th

关 键 词：钛铝基合金 高温拉伸 超塑性 组织演化 电子背散射衍射 

分 类 号：TG146.2[一般工业技术—材料科学与工程]