固溶温度对TC4钛合金微观组织和动态拉伸力学性能的影响

Effect of solid solution temperature on the microstructure and dynamic tensile mechanical properties of TC4 titanium alloy

摘要:

为揭示固溶温度(850 ℃,920 ℃,960 ℃)对TC4钛合金微观组织和动态拉伸力学性能的影响,采用XRD、SEM和EBSD方法对材料晶体结构、微观组织和晶粒取向等特征进行分析,选取分离式霍普金森拉杆(SHTB)实验装置进行了材料的动态拉伸力学性能测试,构建了Johnson-Cook(J-C)本构模型,开展了动态拉伸断口形貌分析。结果表明：随固溶温度升高,材料中α/α′含量升高,初生α相含量降低,针状α′含量升高,晶粒尺寸减小且择优取向强度增大；TC4钛合金具有明显的应变率强化效应,随固溶温度升高,材料屈服强度和维氏硬度逐渐增大,断裂延伸率降低；动态拉伸断口整体表现为韧性断裂,随固溶温度升高,材料塑性降低,固溶温度960 ℃时,试样韧性断裂特征不显著。本文结论可为TC4钛合金力学性能调控及抗冲击设计提供方法和数据支撑。

Abstract:

To reveal the effects of solid solution temperatures (850 °C, 920 °C, 960 °C) on the microstructure and dynamic tensile mechanical properties of TC4 titanium alloy, XRD, SEM and EBSD methods were applied to analyze the characteristics of crystal structure, microstructure, and grain orientation of the material. The separated Hopkinson tension bar (SHTB) experimental device was used for dynamic tensile mechanical property testing of the material, and the Johnson-Cook (J-C) constitutive model was established. Finally, dynamic tensile fracture morphology analysis was performed. Results show that with the increase of solid solution temperature, the content of α/α′phase increases, the content of primary α phase decreases and the content of needle-like α′ phase increases, while the grain size decreases and the strength of selective orientation increases. TC4 titanium alloy exhibits a significant strain rate strengthening effect. With the increase of solid solution temperature, the material yield strength and Vickers hardness gradually increase, and the fracture elongation decreases. The dynamic tensile fracture exhibits ductile fracture characteristics, and with the increase of solution temperature, the plasticity of the material decreases. When the solid solution temperature is 960 ℃, the ductile fracture characteristics of the specimen are not significant. The conclusions of this paper can provide methods and data to support the mechanical property control and impact resistance design of TC4 titanium alloy.