由晓晓,常玲,吕俊霞.原位SEM研究LDMD Ti-6Al-4V合金β晶界对拉伸断裂行为的影响[J].表面技术,2019,48(5):97-101.
YOU Xiao-xiao,CHANG Ling,LYU Jun-xia.In-situ SEM Study of the Effect of β Grain Boundary on the Fracture Behavior of Laser Direct Melting Deposition Ti-6Al-4V Alloy[J].Surface Technology,2019,48(5):97-101 |
| 原位SEM研究LDMD Ti-6Al-4V合金β晶界对拉伸断裂行为的影响 |
| In-situ SEM Study of the Effect of β Grain Boundary on the Fracture Behavior of Laser Direct Melting Deposition Ti-6Al-4V Alloy |
| 投稿时间：2018-10-26 修订日期：2019-05-20 |
| DOI：10.16490/j.cnki.issn.1001-3660.2019.05.015 |
| 中文关键词: 激光直接熔化沉积 增材制造 Ti-6Al-4V合金 原位SEM拉伸 β晶界 |
| 英文关键词:laser direct melting deposition additive manufacturing Ti-6Al-4V alloy in-situ SEM tensile testing β grain boundary |
| 基金项目:国家自然科学基金青年基金（51505010） |
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| 中文摘要: |
| 目的 研究β晶界对激光直接熔化沉积（LDMD）Ti-6Al-4V合金裂纹形核或传播行为的影响，以澄清合金的断裂机制，为合金性能的改善提供理论依据。方法 采用LDMD Ti-6Al-4V合金粉末，在Ti-6Al-4V基板上逐层堆积形成沉积层。沿沉积层扫描方向截取试样，在室温下观察样品的微观组织形貌，并对原位拉伸过程中的微观组织演化进行实时研究。同时研究β晶界对微裂纹萌生、扩展和断裂的影响行为，总结断裂机理。结果 LDMD Ti-6Al-4V合金组织宏观呈现出沿构造方向生长的粗大柱状β晶，β晶内由板条状α晶和整齐排列的具有相同生长取向的α簇组织组成，并有少量孔洞缺陷。采用原位扫描电镜拉伸样品时发现，在横向拉力作用下，样品最初在孔洞周围发生变形，之后裂纹的萌生扩展主要沿β晶界进行，β晶界对拉力起阻碍作用，造成样品的伸长率较低。拉伸过程中，微观组织主要沿着β晶界周围的α相变形，并且孔洞缺陷引起的应力集中使得缺陷周围变形最严重，变形方向与拉力方向呈45°。结论 孔洞缺陷决定了样品的初始变形位置，而β晶界则决定了裂纹传播的方向，且由于拉伸试样的截取方向与β晶界相垂直，导致样品的伸长率较低，所以β晶界对样品的力学性能及断裂机理起决定作用。 |
| 英文摘要: |
| The work aims to clarify the fracture mechanism of laser direct melting deposition (LDMD) Ti-6Al-4V alloy by studying the effect of β grain boundary on the nucleation or propagation behavior of cracks, and provide a theoretical basis for improving the mechanical properties of the alloy. The build was formed on Ti-6Al-4V substrate with LDMD Ti-6Al-4V alloy powder. Samples were taken along the scanning direction of the build. The microstructures of the sample and the real-time changes of the microstructure during in-situ tensile test were studied at room temperature. The effect of β grain boundary on crack initiation, propagation and fracture in tensile test was also investigated, and the fracture mechanism was summarized. The microstructure of the LDMD Ti-6Al-4V sample was composed of coarse columnar β grain that grew parallel to the direction of the build macroscopically. Within the β grain, plenty of lamellar α and α colonies with the same orientation in α plates were observed. Hole defects in a small amount were also identified. The tensile sample by in-situ SEM showed that under the transverse tensile load, the initial deformation of the sample was formed around the hole due to the stress concentration and the crack propagated along the β grain boundary. The β grain boundary hindered the tensile force and resulted in the lower elongation of the sample. During the tensile, the microstructure mainly deformed along phase α surrounding β grain boundary and the hole defects caused more serious deformation due to concentration of stress. There was an angle of 45° between the deformation direction and the tensile direction. The hole defect determines the initial deformation position of the sample, and the β grain boundary determines the direction of crack propagation. Since the direction of the tensile specimen taken is perpendicular to the β grain boundary and the sample has a lower elongation, so β grain boundary plays an important role in mechanical properties and fracture mechanism of sample. |
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