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| 铸态Ti-47Al-2Cr-2Nb合金热变形行为与组织性能研究 |
| Hot Deformation Behavior, Microstructure and Properties of As-cast Ti-47Al-2Cr-2Nb Alloy |
| Received:March 26, 2024 |
| DOI：10.3969/j.issn.1674-6457.2024.11.015 |
| 中文关键词: TiAl合金 压缩成形 微观组织 力学性能 动态再结晶 |
| 英文关键词: TiAl alloy compression forming microstructure mechanical property dynamic recrystallization |
| 基金项目:湖北省重点研发计划(2021baa200，2022aaa001);湖北省自然科学基金(2023AFA069);湖北省隆中实验室自主创新项目(2022ZZ-04) |
| Author Name | Affiliation | | HU Zhijun | Hubei Key Laboratory of Advanced Technology for Automotive Components,Hubei Collaborative Innovation Center for Automotive Components Technology, c.Hubei Engineering Research Center for Green & Precision Material Forming, Wuhan University of Technology, Wuhan 430070, China | | ZHANG Jiaheng | Hubei Key Laboratory of Advanced Technology for Automotive Components,Hubei Collaborative Innovation Center for Automotive Components Technology, c.Hubei Engineering Research Center for Green & Precision Material Forming, Wuhan University of Technology, Wuhan 430070, China | | HU Zhili | Hubei Key Laboratory of Advanced Technology for Automotive Components,Hubei Collaborative Innovation Center for Automotive Components Technology, c.Hubei Engineering Research Center for Green & Precision Material Forming, Wuhan University of Technology, Wuhan 430070, China | | PANG Qiu | School of Mechanical and Electrical Engineering, Wuhan Donghu University, Wuhan 430212, China |
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| 中文摘要: |
| 目的 针对铸态TiAl合金晶粒组织粗大、成形性差等问题，以铸态Ti-47Al-2Cr-2Nb合金为研究对象，探究其高温变形微观组织演变规律和力学性能变化，确定最佳工艺参数。方法 采用MMS-200热力模拟试验机在温度为1 300~1 400 ℃、应变速率为0.02~0.2 s−1、变形量为50%条件下对铸态Ti-47Al-2Cr-2Nb合金进行压缩成形并空冷至室温。采用光学显微镜、扫描电子显微镜、电子背散射衍射仪、维氏硬度计及电子万能试验机研究了试样热压缩变形后的微观组织演变规律和变形后的力学性能。结果 随变形温度的升高和应变速率的减小，合金的动态再结晶程度增加，晶粒尺寸明显细化，在1 400 ℃-0.02 s−1变形条件下，原始粗大片层团破碎最彻底，形成均匀细小的近片层组织，片层团晶粒尺寸由铸态的毫米级细化至20 μm左右，平均片层间距减小至50 nm，维氏硬度达到479HV且沿横截面分布较为均匀。经1 400 ℃-0.02 s−1热锻成形后，合金的室温压缩屈服强度和800 ℃压缩屈服强度分别达到958 MPa和492 MPa，相比于原始铸态合金，分别提高了123.8%和52.3%。结论 在1 400 ℃-0.02 s−1条件下进行热压缩变形时，α相发生了完全的动态再结晶，形成细小等轴晶，在随后的空冷过程中形成精细的片层结构，合金综合力学性能达到最优。 |
| 英文摘要: |
| In response to issues such as coarse grain structure and poor formability of as-cast TiAl alloys, the work aims to focus on the as-cast Ti-47Al-2Cr-2Nb alloy to investigate its high-temperature deformation microstructure evolution and mechanical property changes, so as to determine the optimal process parameters. The MMS-200 thermal simulation machine was employed to perform compression forming of the as-cast Ti-47Al-2Cr-2Nb alloy at the temperature ranging from 1 300 to 1 400 ℃ under the strain rate of 0.02 s−1 to 0.2 s−1 and the deformation amount of 50%, followed by air cooling to room temperature. The microstructure evolution and mechanical properties of the specimens after hot compression deformation were investigated with optical microscopy, scanning electron microscopy, electron backscatter diffraction, Vickers hardness tester, and universal testing machine. With the increasing deformation temperature and the decreasing strain rate, the degree of dynamic recrystallization of the alloy increased, and the grain size significantly refined. Under the condition of deformation at 1 400 ℃ and 0.02 s−1, the original coarse lamellar colonies were thoroughly fragmented, forming a uniformly fine near-lamellar structure. The grain size of lamellar colonies decreased from the millimeter level in the as-cast state to around 20 μm, and the average lamellar spacing decreased to 50 nm, the Vickers hardness reached 479HV and distributed more uniformly along the cross section. After hot forging at 1 400 ℃ and 0.02 s−1, the compressive yield strength of the alloy at room temperature and 800 ℃ reached 958 MPa and 492 MPa, respectively, representing an increase of 123.8% and 52.3% compared to that of the original as-cast alloy. During hot compression deformation at 1 400 ℃ and 0.02 s‒1, the α phase undergoes complete dynamic recrystallization, forming fine equiaxed grains and subsequently forming a refined lamellar structure during the subsequent air cooling process. The comprehensive mechanical properties of the alloy reach the optimal level under these conditions. |
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