选区激光熔化制备Ti-6Al-4V合金的热处理工艺及力学性能

doi:10.13251/j.issn.0254-6051.2022.09.031

摘要/Abstract

摘要： 采用选区激光熔化技术(SLM)制备Ti-6Al-4V合金圆棒试样,通过不同的热处理工艺改善材料的拉伸性能,并对SLM制备的Ti-6Al-4V合金试样开展了高周疲劳性能测试。通过微观组织和疲劳试样断口分析,揭示了显微组织结构与拉伸性能的关系,以及Ti-6Al-4V合金的疲劳裂纹起始源和裂纹扩展机理。结果表明,热处理工艺对SLM成型Ti-6Al-4V合金的力学性能有显著的影响,920 ℃×1 h水冷,随后800 ℃×2 h炉冷的固溶时效热处理制度可以获得较好的综合室温拉伸性能。其室温组织为晶界上分布的α相和晶粒内部片层状分布的α+β相。SLM成型Ti-6Al-4V合金显微组织中的晶界形成与扫描路径相关,热处理过程中α相会优先在扫描分区搭接处析出。与手册锻件的疲劳寿命曲线比较,在同样的最大应力水平下,增材试样的疲劳寿命比锻件的疲劳寿命低,这种降低的趋势随着应力水平的降低而逐步增大。在400 MPa的应力水平下(R=-1),锻件的疲劳寿命已经在2×10⁷水平,增材试样的疲劳寿命依然较低,约为锻件的1%。SLM成型Ti-6Al-4V合金的应力疲劳寿命偏低,是由于试样中存在未熔合缺陷造成。扫描分区搭接处易产生未熔合缺陷,而疲劳裂纹也会沿着这些缺陷扩展。

关键词: 增材制造, Ti-6Al-4V合金, 热处理, 力学性能

Abstract: Ti-6Al-4V alloy round bar specimens were prepared by the selective laser melting(SLM) technology, and the tensile properties of the material were improved by different heat treatment processes. The high cycle fatigue properties of the Ti-6Al-4V alloy were also tested. The relationship between microstructure and tensile properties, as well as the fatigue crack initiation source and crack propagation mechanism of the Ti-6Al-4V alloy were revealed by microstructure and fracture analysis. The results show that the heat treatment process has a significant effect on the mechanical properties of the Ti-6Al-4V alloy fabricated by SLM. The solution aging heat treatment process at 920 ℃×1 h, water-rolling and 800 ℃×2 h, furnace-cooling exhibit preferable comprehensive tensile properties at room temperature. The microstructure at room temperature is composed of α phase on the grain boundary and lamellar α+β microstructure inside the grain. The formation of grain boundary in the Ti-6Al-4V alloy microstructure is related to scanning path of additive manufacturing process. During the heat treatment, α phase precipitate preferentially at the overlap of scanning zone. Compared with the fatigue life curve of the forgings, the fatigue life of the SLMed specimens is lower at the same maximum stress level, and the decreasing trend increases with the decrease of the stress level. At 400 MPa stress level R=-1, the fatigue life of the forgings has reached 2×10⁷ level, and the fatigue life of the SLMed specimens is low, only 1% of that of the forgings. The low stress fatigue life is due to the existence of faulty fusion in the SLMed specimens. The faulty fusion is easy to appear at the overlap of scanning zone, and the fatigue crack will also propagate along these defects.

Key words: additive manufacture, Ti-6Al-4V alloy, heat treatment, mechanical properties

中图分类号:

李颖, 彭霜, 张婷, 柴象海, 翁依柳. 选区激光熔化制备Ti-6Al-4V合金的热处理工艺及力学性能[J]. 金属热处理, 2022, 47(9): 175-181.

Li Ying, Peng Shuang, Zhang Ting, Chai Xianghai, Weng Yiliu. Heat treatment process and mechanical properties of selective laser melted Ti-6Al-4V alloy[J]. Heat Treatment of Metals, 2022, 47(9): 175-181.

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