Effect of wire feed rate on microstructure and properties of laser welded Ti-3Al-6Mo-2Fe-2Zr joints with filler wire
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摘要: 采用Ti-6Al-4V(TC4)焊丝对2 mm厚的Ti-3Al-6Mo-2Fe-2Zr钛合金进行激光填丝焊接，利用光学显微镜、扫描电子显微镜、X射线能谱仪等分析测试方法研究了送丝速度对接头显微组织和力学性能的影响. 结果表明，由于从熔合线至母材受到焊接热作用逐渐递减，热影响区组织依次为单一β相、基体β相 + 初生αp相、基体β相 + 初生αp相 + 少量次生αs相. 焊缝中有针状α'相生成，且分布不均匀. 随着送丝速度的增加，针状α'相的数量增加，尺寸增大. 激光填丝焊接头的抗拉强度及断后伸长率均低于母材，随送丝速度的增加，接头抗拉强度上升，断后伸长率下降.其原因在于TC4焊丝的加入，促使针状α'相在焊缝中析出，送丝速度加快，造成焊缝中钼当量[Mo]eq降低，析出的针状α'相数量进一步增多，尺寸增大. 针状α'相的析出提高了焊缝强度，当送丝速度大于1.0 m/min时，接头的断裂位置为热影响区.Abstract: The Ti-6Al-4V(TC4) filler wire was used to join 2 mm thick Ti-3Al-6Mo-2Fe-2Zr titanium alloy during laser welding process. Investigations concerning the influence of wire feeding rate on microstructure and tensile properties were conducted on laser welded Ti-3Al-6Mo-2Fe-2Zr joints with filler wire by optical microscope, scanning electron microscope, and X ray energy spectrometer and other analytical testing methods. The results show that, due to the decreasing heat effect from fusion line to base metal, the microstructure of the heat affected zone is divided as follows: single β region, primary α + matrix β region, and primary α + retained secondary α + matrix β region. Acicular α' phase is formed in the fusion zone, and the distribution is not uniform. As the wire feed speed increases, the number and size of acicular α' phase increases. The tensile strength and elongation of laser welded joints with filler wire are lower than those of the base metal. With the increase of wire feeding rate, the tensile strength of the joint increases and the elongation decreases. The reason is attributed to that, as the wire feeding rate increased, the [Mo]eq in the fusion zone decreased correspondingly, which led to the increment in the number and size of α' phase. When the wire feeding rate was higher than 1.0 m/min, the fracture location changed from fusion zone to heat affected zone because of the strengthening effects of α' phase.
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Keywords:
- laser welding with filler wire /
- β titanium alloy /
- microstructure /
- tensile property
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图 4 热影响区微观组织
Figure 4. Microstructure of heat affected zone (HAZ). (a) region 1; (b) region 2; (c) region 3
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图 6 焊缝微观组织
Figure 6. Microstructure of weld. (a) F1 weld (vf = 1.0 m/min, low magnification); (b) F2 weld (vf = 1.5 m/min, low magnification); (c) F3 weld (vf = 2.0 m/min, low magnification); (d) F1 weld (vf = 1.0 m/min, high magnification); (e) F2 weld (vf = 1.5 m/min, high magnification); (f) F3 weld(vf = 2.0 m/min, high magnification)
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图 8 拉伸试样断裂位置
Figure 8. Fracture location of tensile specimen. (a) vf = 1.0 m/min; (b)vf = 1.5 m/min; (c) vf = 2.0 m/min
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图 9 激光焊接头的断口形貌
Figure 9. Fracture morphology of laser welded joints. (a) BM; (b) vf = 1.0 m/ min; (c) vf = 1.5 m/min; (d) vf = 2.0 m/min
表 1 Ti-3Al-6Mo-2Fe-2Zr和TC4焊丝化学成分(质量分数，%)
Table 1 Chemical compositions of Ti-3Al-6Mo-2Fe-2Zr and TC4 filler wire
材料 Ti Al Fe Zr Mo V Ti-3Al-6Mo-2Fe-2Zr 83.97 3.31 2.89 2.12 7.71 — TC4 89.642 6.24 0.048 — — 4.07 
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表 2 焊接工艺参数
Table 2 Welding process parameters
试样
编号送丝速度
vf /(m·min−1)焊接速度
v/(m·min−1)激光功率
P/W气体流量Q/(L·min−1) 正面 背面 F1 1.0 1.0 1 400 20 3 F2
F31.5
2.01.0
1.01 400
1 40020
203
3
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表 3 焊缝能谱分析
Table 3 Energy spectrum analysis for the welds
试样编号 原子分数a(%) 钼当量[Mo]eq(%) Al Ti V Fe Zr Mo F1 4.84 85.34 0.87 1.86 1.78 5.31 9.65 F2 4.85 86.25 1.42 1.53 1.52 4.43 8.50 F3 5.24 87.03 1.88 1.27 1.18 3.40 7.28
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