Heat treatment process and mechanical properties of selective laser melted Ti-6Al-4V alloy

doi:10.13251/j.issn.0254-6051.2022.09.031

Abstract

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

CLC Number:

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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