TC4钛合金电子束焊接头微观组织结构和演变分析

摘要

Microstructure of electron beam welded TC4 joint is investigated through OM, SEM, EDS and EBSD analysis. Results show that the microstructure in the fusion zone (FZ) and heat affected zone (HAZ) change signiifcantly after electron beam welding. The FZ is made up of coarse columnar grains with matensite α’, and the misorientation angle distribution concentrates near 62.5°,which represents part α/α boundaries are formed from one parentβgrain. Due to the welding thermal cycle, the original texture microstructure is transformed into equiaxed grains in HAZ near base metal (BM). The micro-structure of HAZ near BM is composed of originalα, origi-nalβ, blockαand few matensiteα’, and the misorientation angle distribution indicates partα/αboundaries are devel-oped from two differentβgrains. HAZ near FZ is made up of matensiteα’ and blockα, and the misorientation angle distribution represents partα/αboundaries are formed from one parentβgrain..%利用OM、SEM、EDS和EBSD方法对TC4合金电子束焊接头的微观组织结构进行了分析。结果表明：电子束焊接后，接头微观组织结构发生显著改变。焊缝区为内含针状马氏体α’组织的粗大柱状晶，部分取向差集中于62.5°附近，表明较多α/α边界由同一β相晶粒产生。热影响区微观组织结构复杂，母材侧热影响区，经焊接热循环，原始择优取向特征消失，出现等轴特征，组织由原始α相、原始β相、块状α相和少量的针状马氏体α’组织组成，部分取向差集中于40.0°附近，表明较多的α相在不同的β相晶粒中产生。焊缝侧热影响区，因热循环峰值温度超过β相转变温度，且冷却速度较快，产生大量的针状马氏体α’组织以及少量块状α组织，部分取向差集中于62.5°附近，表明较多α/α边界由同一β相晶粒产生。