In this study,the stress relaxation(SR)behaviors of a Ti-6AI-4V alloy pre-loaded from elastic to plastic regions and corresponding strength evolution mechanisms at different temperatures were systematically studied.In order to quantitatively analyze the detailed deformation and strength evolution mechanisms during the whole SR tests,which is composed of the loading stage and subsequent SR stage,the evolu-tions of α/β structures and dislocations have been identified by a series of microstructural observations,i.e.,scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),high resolution trans-mission electron microscopy(HRTEM),energy dispersive spectroscopy(EDS).A great quantity of entan-gled dislocations in α phase introduced by the plastic loading at temperatures below 800℃promotes the emergence of SR behavior with a higher creep rate,leading to the much higher SR level with larger pre-load levels.Diffusion is significantly enhanced by dislocations accumulated at interfaces with higher temperatures(＞800℃),contributing to a similar SR phenomenon under different initial strain levels.Apparent strength loss has been observed after SR with high temperatures or pre-loaded to the plastic region,e.g.,94 MPa loss for 800℃,pre-loaded with a stain of 10％and SR for 2400 s.The strength loss mainly comes from the loading stage where distorted and fragmented β layers occur.The subsequent SR stage facilitates interfacial diffusion and results in a higher fraction of granular β phases,leading to a further decrease in yield strength(YS).This study enhances the understanding on the deformation and strength evolution mechanisms of titanium alloys with lamellar structures in the whole SR process,pro-viding a physical foundation for optimizing the processing parameters for manufacturing titanium alloy components with high accuracy and performance.

School of Mechanical Engineering and Automation,Beihang University,Beijing 100191,China;Institute of Metals,College of Materials Science and Engineering,Changsha University of Science&Technology,Changsha 410004,China;School of Materials Science and Engineering,Beihang University,Beijing 100191,China

[1]Ying Zhang;Dongsheng Li;Xiaoqiang Li;Xiaochun Liu;Shiteng Zhao;Yong Li-.Creep deformation and strength evolution mechanisms of a Ti-6Al-4V alloy during stress relaxation at elevated temperatures from elastic to plastic loading)[J].材料科学技术（英文版）,2022(31):93-105

6AI

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