Research on heat treatment properties of TC4 titanium alloy based on electron beam additive manufacturing
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摘要: 将电子束选区熔化制备的试件增加热处理工艺，利用扫描电子显微镜和金相显微镜研究了热处理后TC4钛合金试件的组织特征；并通过试件力学性能的变化，揭示了不同热处理工艺选择对电子束选区熔化成形产品的影响。结果表明：不论是空冷处理还是炉冷处理，试件在相变点温度以下加热其抗拉强度提升，在相变点温度以上加热其抗拉强度会下降。通过观察微观组织与分析拉伸断口可知，TC4钛合金试件在经过950 ℃和1 000 ℃热处理的组织由于β相转变为魏氏组织而抗拉强度下降；而加热至850 ℃时由于未达到相变点温度，其内部为网篮组织而性能稳定。恰当的热处理工艺能使增材制造成形的TC4钛合金的抗拉强度等力学性能更优。Abstract: In this paper, heat treatment was carried out for TC4 titanium alloy specimens prepared by electron beam selective melting. The microstructure characteristics of the TC4 titanium alloy specimens after heat treatment were studied by using scanning electron microscope and metallographic microscope. The mechanical properties of the TC4 titanium alloy specimens were investigated. The influence of heat treatment process on the specimen was revealed. The results show that the tensile strength of the specimens increased via heat treatment below phase transition temperature with the air cooling or furnace cooling, while the tensile strength of the specimens decreased by heat treatment at temperatures higher than the phase transition point. By observing the microstructure and analyzing the tensile fracture, it is found that the tensile strength of TC4 titanium alloy specimens decreased via heat treatment at 950 ℃ and 1 000 ℃, due to the transformation of β phase into Widmanstatten structure. However, at 850 ℃ of heat treatment temperature, the properties of the TC4 titanium alloy specimens were stable, because the microstructure inside was still equiaxed before reaching the phase transition point. Those results suggest the TC4 titanium alloy manufactured by EBSM have good mechanical properties by an appropriate heat treatment process.
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Key words:
- Ti-6Al-4V /
- EBSM /
- heat-treatment /
- mechanical property
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图 4 不同热处理工艺的钛合金试件30倍断口形貌
Figure 4. Fracture morphology of titanium alloy specimens with different heat treatment processes at 30x
图 6 不同热处理工艺的钛合金试件1 000倍及5 000倍断口形貌
Figure 6. Fracture morphology of titanium alloy specimens with different heat treatment processes at 1 000x and 5 000x
图 7 不同热处理工艺的钛合金试件金相组织
Figure 7. Metallographic microstructure of titanium alloy specimens with different heat treatment processes
表 1 Ti-6Al-4V ELI粉末化学成分
Table 1. Chemical constituents of Ti-6Al-4V ELI powder
% Al V C Fe O N H Ti 6 4 0.03 0.1 0.1 0.01 0.003 Balance 
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表 2 钛合金试件热处理工艺参数
Table 2. Heat treatment process parameters of titanium alloy specimen
序号 加热温度/℃ 保温时间/h 冷却方式 1 850 1 空冷 2 950 1 空冷 3 1000 1 空冷 4 850 1 炉冷 5 950 1 炉冷 6 1000 1 炉冷 7 常态 常态 常态
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表 3 拉伸试件室温拉伸力学性能
Table 3. Tensile mechanical properties of titanium alloy specimens
试件编号 抗拉强度/MPa 屈服强度/MPa 断面收缩率/% 常态 740.52 739.60 32.3 FC850 762.82 762.21 24.3 FC950 686.94 309.14 19.5 FC1000 544.23 244.87 9.1 AC850 747.14 734.91 20.1 AC950 727.28 352.23 17.2 AC1000 555.44 249.56 11.2
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