High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation ...High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.展开更多
Hydraulic fracturing in the soil core of earth-rockfill dams is a common problem affecting the safety of the dams. Based on fracture tests, a new criterion for hydraulic fracturing in cohesive soil was suggested. Usin...Hydraulic fracturing in the soil core of earth-rockfill dams is a common problem affecting the safety of the dams. Based on fracture tests, a new criterion for hydraulic fracturing in cohesive soil was suggested. Using this criterion, the mechanisms of hydraulic fracturing in cubic soil specimens were investigated. The results indicate that the propagation of the crack in a cubic specimen under water pressure occurs in a mixed mode I-II if the crack face is not perpendicular to any of the principal stresses, and the crack most likely to propagate is the one that is perpendicular to the minor principal stress and propagates in mode I.展开更多
High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of mi...High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.展开更多
The final mechanical properties of components greatly depend on their grain size. It is necessary to study the grain evolution during different thermomechanical processes. In the study, the real-time austenite grain e...The final mechanical properties of components greatly depend on their grain size. It is necessary to study the grain evolution during different thermomechanical processes. In the study, the real-time austenite grain evolution of a high-strength low-alloy(HSLA) steel during the soaking process is investigated by in situ experiments. The effects of different deformation parameters on the dynamic recrystallization(DRX) kinetic behaviors are investigated by hot compression experiments. Based on the observations and statistics of the microstructures at different thermomechanical processes, a unified grain size model is established to evaluate the effects of soaking parameters and deformation parameters on the austenite grain evolution. Also, the DRX kinetic model and critical strain model are established, which can describe the effects of the soaking process on the DRX kinetics process well. The established grain size model and DRX kinetic model are compiled into the numerical simulation software using Fortran language. The austenite grain evolution of the material under different deformation conditions is simulated, which is consistent with the experimental results. It indicates that the established model is reliable, and can be used to simulate and predict the grain size during different thermomechanical processes accurately.展开更多
基金supported by the Project of National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, China (No. 6142909190207)Shaanxi Key Laboratory of High-performance Precision Forming Technology and Equipment (SKL-HPFTE), China (No. PETE-2019-KF-01)。
文摘High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.
基金supported by the National Natural Science Foundation of China (Grant No. 50779081)the Key Project of the Chinese Ministry of Education (Grant No. 208114)the Science and Technology Project of the Chongqing Municipal Education Commission of China (Grant No. KJ080428)
文摘Hydraulic fracturing in the soil core of earth-rockfill dams is a common problem affecting the safety of the dams. Based on fracture tests, a new criterion for hydraulic fracturing in cohesive soil was suggested. Using this criterion, the mechanisms of hydraulic fracturing in cubic soil specimens were investigated. The results indicate that the propagation of the crack in a cubic specimen under water pressure occurs in a mixed mode I-II if the crack face is not perpendicular to any of the principal stresses, and the crack most likely to propagate is the one that is perpendicular to the minor principal stress and propagates in mode I.
基金the project of National Key Laboratory for Precision Hot Processing of Metals,Harbin Institute of Technology(No.6142909190207)Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment(NSKL-HPFTE)(No.PETE-2019-KF01)。
文摘High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.
基金funded by the National Key Research and Development Program of China(Grant No.2018YFB1106003)the National Natural Science Foundation of China(Grant No.51435007)+1 种基金the Fundamental Research Funds for the Central Universities,HUST(Grant No.2020JYCXJJ057)。
文摘The final mechanical properties of components greatly depend on their grain size. It is necessary to study the grain evolution during different thermomechanical processes. In the study, the real-time austenite grain evolution of a high-strength low-alloy(HSLA) steel during the soaking process is investigated by in situ experiments. The effects of different deformation parameters on the dynamic recrystallization(DRX) kinetic behaviors are investigated by hot compression experiments. Based on the observations and statistics of the microstructures at different thermomechanical processes, a unified grain size model is established to evaluate the effects of soaking parameters and deformation parameters on the austenite grain evolution. Also, the DRX kinetic model and critical strain model are established, which can describe the effects of the soaking process on the DRX kinetics process well. The established grain size model and DRX kinetic model are compiled into the numerical simulation software using Fortran language. The austenite grain evolution of the material under different deformation conditions is simulated, which is consistent with the experimental results. It indicates that the established model is reliable, and can be used to simulate and predict the grain size during different thermomechanical processes accurately.
