焊接速度对TC18钛合金厚板电子束焊接接头疲劳性能的影响

Effect of Welding Speed on Fatigue Properties of TC18 Thick Plate by Electron Beam Welding

摘要:

采用电子束焊接的方法,实现了15mm TC18钛合金厚板的焊接。利用光学显微镜、扫描电镜及透射电子显微镜对接头的宏观形貌、显微组织及断口特征进行分析,并用电子万能试验机测试了接头的疲劳性能,研究了不同焊接速度(10 mm/s、20mm/s、30mm/s)对TC18钛合金厚板电子束焊接接头疲劳性能的影响。结果表明,焊缝熔合区主要由柱状的β相和针状的α马氏体相组成。随着焊接速度的增加,焊缝区上熔宽、中熔宽、下熔宽都呈明显减少,焊缝区晶粒细化,导致焊接接头疲劳性能增加。在Nf =107时,随焊接速度从10mm/s增加到30mm/s,焊缝疲劳极限提高近29%。接头疲劳试验断口可分为疲劳裂纹源区、裂纹扩展区和裂纹瞬断区三个典型区域,疲劳裂纹都起源于试件表面,随着焊接速度增大,瞬断区占的比例减小,疲劳性能增强。

Abstract:

The welding of 15mm TC18 titanium alloy thick plate is realized by electron beam welding. The effect of different welding speeds (10 mm / s, 20 mm / s, 30mm / s) on the fatigue properties of the electron beam welded joints for TC18 titanium alloy was investigated. The macroscopic morphology, microstructure and fracture characteristics of the joints were analyzed by optical microscope, scanning electron microscopy and transmission electron microscopy, and the fatigue properties of welded joints were studied and tested by an electronic universal testing machine. The results showed that the weld fusion zone was mainly composed of columnar β phase and acicular α martensite phase. The upper melting width, the middle melting width and the lower melting width were obviously reduced, and the grain size gradually decreased with the increased of welding speed, which resulted in the increase of fatigue properties of welded joints. At Nf =107, the fatigue limit of the weld was increased by nearly 29% with the welding speed from 10mm/s to 30mm/s. The fatigue fracture of the joints can be divided into three typical regions of fatigue crack source zone, expansion zone and instantaneous zone, and the fatigue cracks all originated from the surface of the specimen. With the increased of welding speed, the proportion of instantaneous area decreased and the fatigue performance increased.