双重退火对TC4-DT/TC21线性摩擦焊接头组织及力学性能影响  

Microstructure and Mechanical Properties of TC4-DT/TC21 Linear Friction Welded Joint with Duplex Annealing

作　　者：高潘 曾卫东[1] 张传臣 徐建伟[1] Gao Pan;Zeng Weidong;Zhang Chuanchen;Xu Jianwei(State Key Laboratory of Solidification Technology,National Defense Technology Industry Precision Forging and Ring Rolling Technology Innovation Center,Institute of Materials Science and Technology,Shaanxi Provincial Key Laboratory of High-Performance Precision Forming Technology and Equipment,Northwestern Polytechnical University,Xi'an 710072,China;Aviation Technology Key Laboratory of Aviation Welding and Joining Technology,China Academy of Aviation Manufacturing Technology,Beijing 100024,China)

机构地区：[1]西北工业大学材料学院凝固技术国家重点实验室,国防科技工业精密锻造与环轧技术创新中心,陕西省高性能精确成形技术与装备重点实验室,陕西西安710072 [2]中国航空制造技术研究院航空焊接与连接技术航空科技重点实验室,北京100024

出　　处：《稀有金属》2024年第1期1-10,共10页Chinese Journal of Rare Metals

基　　金：航空科学基金项目(201911053001)资助。

摘　　要：对TC4-DT/TC21异种钛合金线性摩擦焊接头进行双重退火处理,对比分析双重退火对接头微观组织及力学性能的影响。结果表明:经双重退火后,焊缝中心区内针状组织发生粗化,其平均宽度由0.2μm增加至0.5~1.0μm;热力影响区内,沿震荡方向以波纹状分布的初生α相在畸变能释放以及元素扩散的作用下变形程度降低,且α_(p)相周围的针状α相也长大为竹叶状;母材区内,在α_(p)发生球化的同时还在β基体上析出针状α相。较于热处理前的力学性能(抗拉强度(R_(m))=911 MPa,断后伸长率(A)=8.5%),经过较低温度的双重退火(PWHT 1)处理后,在组织粗化及针状α相析出的共同作用下接头强度和断后伸长率都有所降低(R_(m)=886 MPa,A=6.0%)。但经过较高温度的双重退火(PWHT 2)处理后,弥散分布的针状次生α相显著提升材料的强度,且塑性仍保持较高的水平(R_(m)=925 MPa,A=6.2%)。对于拉伸断口,双重退火后裂纹扩展区主要是韧窝+撕裂棱和小解理刻面的混合,且裂纹在扩展过程大多与α片层呈一定角度进行扩展,说明在拉伸过程中接头的失效形式为穿晶的韧性-脆性混合断裂。对于接头的冲击韧性,较于热处理前14.8 J的冲击吸收功,双重退火能显著提升接头的冲击韧性,且随着第一次退火温度的升高,接头冲击吸收功由38.6 J增加至41.2 J。As a solid-state connection technology,linear friction welding is widely used in the connection of various alloys due to its advantages of fewer defects and low cost.However,the mechanical properties of the joints will be significantly reduced by residual stress and metastable phases,so the heat treatment of the joints is necessary.Recently,the post-weld heat treatment of TC4-DT/TC21linear friction welded joints was mainly focused on simple annealing at low temperatures,which couldn’t significantly change the microstructure characteristics of the joints.In order to fully understand the effect of post-weld heat treatment on TC4-DT/TC21 linear friction welding joints,two different duplex annealing (PWHT 1:840℃/1 h,AC+590℃/4 h,AC;PWHT 2:870℃/1 h,AC+590℃/4 h,AC) was applied to the linear friction welded joint of TC4-DT/TC21 dissimilar titanium alloy,and the effect of duplex annealing on the microstructure and mechanical properties of the joint was analyzed.Optical microscope (OM),scanning electron microscope(SEM) and Vickers hardness tester were used to compare and analyze the microstructure,microhardness and fracture of the joints under different duplex annealing.According to the structural characteristics of TC4-DT/TC21 linear friction welding joint,the joint could be divided into weld center zone (WCZ),thermo-mechanical affect zone (TMAZ) and base metal (BM).After duplex annealing,the structure of each zone had undergone significant changes,and the duplex annealing had great influence on the microstructure of the joint.The average width of the acicular α phases in the weld center zone increased from 0.2 to 0.5~1.0μm after duplex annealing,in the thermal-mechanical affected zone the deformation of the primary wavy α phases in the oscillating direction decreased under the effect of distortion energy release and element diffusion,and the acicular α phases around the primary wavy α phases grew into bamboo leaf shape,in the base metal,the spheroidization of primary α phases occurred and the acicular α

关 键 词：线性摩擦焊 焊后热处理 微观结构 抗拉强度 硬度分布 冲击韧性 

分 类 号：TG166.5[金属学及工艺—热处理]