Tensile and fatigue properties of electron beam welded dissimilar joints between Ti–6Al–4V and BT9 titanium alloys
Tensile and fatigue properties of electron beam welded dissimilar joints between Ti–6Al–4V and BT9 titanium alloys
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DOI：
10.1016/j.msea.2013.07.009
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发表时间：
2013-11
期刊：
影响因子：
6.4
通讯作者：
S. Q. Wang;Junting Liu;D. Chen
中科院分区：
文献类型：
--
作者：
S. Q. Wang;Junting Liu;D. Chen
研究了Ti-6Al-4V与BT9 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si）异种钛合金电子束焊接接头的显微组织、硬度、拉伸和疲劳性能。焊后组织发生明显变化，Ti-6Al-4V侧熔合区（FZ）和热影响区（HAZ）出现马氏体，BT9侧HAZ出现马氏体+部分α相。Ti-6Al-4V /BT9异种接头的硬度分布不对称，FZ区硬度值明显较高，但HAZ区不存在软区。不同接头的极限抗拉强度、单调屈服强度和循环屈服强度、循环应变硬化指数均介于两种贱金属之间。接头和BMs具有几乎相同的单调和循环应力-应变曲线和疲劳寿命，而循环应变硬化指数略高于单调应变硬化指数。尽管在较高应变幅值时发生循环软化，但在较低应变幅值时，BMs和节理均出现循环稳定化，循环稳定化幅度高达0.6%。Ti-6Al-4V合金的异种接头发生疲劳破坏，裂纹起源于试样表面或近表面缺陷，裂纹扩展以疲劳条纹和次生裂纹为特征。
The microstructure, hardness, tensile and fatigue properties of electron beam welded dissimilar joints between Ti–6Al–4V and BT9 (Ti–6.5Al–3.5Mo–1.5Zr–0.3Si) titanium alloys were studied. A marked microstructural change occurred after welding, with martensite in the fusion zone (FZ) and in the heat-affected zone (HAZ) of Ti–6Al–4V side, and martensite plus some retainedαphase in the HAZ of BT9 side. While an asymmetrical hardness profile across the dissimilar joint was observed with significantly higher hardness values in the FZ, no soft zone was present in the HAZ of the Ti–6Al–4V/BT9 dissimilar joints. The ultimate tensile strength, monotonic and cyclic yield strength, and cyclic strain hardening exponent of the dissimilar joints lay in-between those of two base metals (BMs). The joint and BMs had almost the same monotonic and cyclic stress–strain curves and fatigue life, while the cyclic strain hardening exponent was slightly higher than the monotonic strain hardening exponent. Although cyclic softening occurred at higher strain amplitudes, cyclic stabilization appeared at lower strain amplitudes up to 0.6% for both BMs and joints. Fatigue failure of the dissimilar joints occurred in the BM of Ti–6Al–4V, with crack initiation from the specimen surface or near-surface defect and crack propagation characterized by fatigue striations along with secondary cracks.