Metal mineral resources play an indispensable role in the development of the national economy.Dynamic disasters in underground metal mines seriously threaten mining safety,which are major scientific and technological ...Metal mineral resources play an indispensable role in the development of the national economy.Dynamic disasters in underground metal mines seriously threaten mining safety,which are major scientific and technological problems to be solved urgently.In this article,the occurrence status and grand challenges of some typical dynamic disasters involving roof falling,spalling,collapse,large deformation,rockburst,surface subsidence,and water inrush in metal mines in China are systematically presented,the characteristics of mining-induced dynamic disasters are analyzed,the examples of dynamic disasters occurring in some metal mines in China are summarized,the occurrence mechanism,monitoring and early warning methods,and prevention and control techniques of these disasters are highlighted,and some new opinions,suggestions,and solutions are proposed simultaneously.Moreover,some shortcomings in current disaster research are pointed out,and the direction of efforts to improve the prevention and control level of dynamic disasters in China’s metal mines in the future is prospected.The integration of forward-looking key innovative theories and technologies in the abovementioned aspects will greatly enhance the cognitive level of disaster prevention and mitigation in China’s metal mining industry and achieve a significant shift from passive disaster relief to active disaster prevention.展开更多
Dislocation mechanism operating in dynamic recrystallization （DRX） during hot compression of Mg-5.51Zn-0.49Zr alloy was investigated by X-ray diffraction, optical microscopy and transmission electron microscopy. The...Dislocation mechanism operating in dynamic recrystallization （DRX） during hot compression of Mg-5.51Zn-0.49Zr alloy was investigated by X-ray diffraction, optical microscopy and transmission electron microscopy. The results showed that the continuous DRX occurred at a low strain rate of 1×10^-3s^-1, which was associated with the operation of the single gliding dislocation climbing. At the intermediate strain rate of 1×10^-2s^-1, the continuous DRX was associated with the climbing of the gliding dislocation array as deformed at an elevated temperature of 350 ℃, and in contrast, the discontinuous DRX was observed and associated with the bulging of subgrain boundaries as the deformation temperature was raised to 400 ℃. The continuous DRX was associated with the climbing of the leading dislocation ahead of pile-ups, and resultant rearrangement of misorientated flat dislocation pile-ups as the strain rate was increased to 1×100s^-1. It is suggested that the mechanism predominating the dislocation climbing was changed from the vacancy migration to the stress acting on the leading dislocation ahead of the pile-up as the strain rate was gradually increased.展开更多
The flow stress behavior of extruded AZ31 magnesium alloy sheet was investigated by means of compression tests at temperatures between 473 and 523 K and strain rates ranging from 0.001 to 1.0 s-1. The deformation acti...The flow stress behavior of extruded AZ31 magnesium alloy sheet was investigated by means of compression tests at temperatures between 473 and 523 K and strain rates ranging from 0.001 to 1.0 s-1. The deformation activation energy of the sheet in extrusion direction （ED） was calculated, and the relationship between the softening effect and deformation mechanism was elucidated by optical microscopy and transmission electron microscopy. The results show that when the extruded AZ31 magnesium alloy samples were compressed at moderate temperatures in ED direction, the deformation activation energy is 174.18 kJ/mol, which means that dynamic recrystallization （DRX） is the main softening effect and is controlled by cross slip of thermal active dislocation. Dislocation slip is the main deformation mechanism in moderate-temperature deformation process except twinning. The main DRX effect at moderate temperatures can be considered to be continuous dynamic recrystallization accommodated with twinning DRX.展开更多
Dynamic recrystallization (DRX) behavior in β phase region for the burn resistant titanium alloy Ti?25V?15Cr?0.2Si was investigated with a compression test in the temperature range of 950?1100 °C and the strain ...Dynamic recrystallization (DRX) behavior in β phase region for the burn resistant titanium alloy Ti?25V?15Cr?0.2Si was investigated with a compression test in the temperature range of 950?1100 °C and the strain rate of 0.001?1 s?1. The results show that deformation mechanism of this alloy in hot deformation is dominated by DRX, and new grains of DRX are evolved by bulging nucleation mechanism as a predominant mechanism. DRX occurs more easily with the decrease of strain rate and the increase of deformation temperature. Grain refinement is achieved due to DRX during the hot deformation at strain rate range of 0.01?0.1 s?1 and temperature range of 950?1050 °C. DRX grain coarsening is observed for the alloy deformed at the higher temperatures of 1100 °C and the lower strain rates of 0.001 s?1. Finally, in order to determine the recrystallized fraction and DRX grain size under different deformation conditions, the prediction models of recrystallization kinetics and recrystallized grain sizes were established.展开更多
The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repea...The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.展开更多
Split Hopkinson Tension Bar(SHTB) experiments were conducted to explore the dynamic mechanical behavior and deformation mechanism of powder metallurgical(PM) Ti-47 Al-2 Nb-2 Cr-0.2 W(at.%)intermetallics with near lame...Split Hopkinson Tension Bar(SHTB) experiments were conducted to explore the dynamic mechanical behavior and deformation mechanism of powder metallurgical(PM) Ti-47 Al-2 Nb-2 Cr-0.2 W(at.%)intermetallics with near lamellar(NL) and duplex(DP)microstructures. Results show that,under dynamic loading,the high temperature strength of the PM TiAl intermetallics is higher than that under quasi-static loading, and the ductile to brittle transition temperature(DBTT) increases with the increase of strain rate. Formation of twinning and stacking faults is the main deformation mechanism during dynamic loading. The work hardening rates of the PM TiAl intermetallics are nearly insensitive to strain rate and temperature at high strain rates(800-1600 s-1)and high temperatures(650-850 ℃). Zerilli-Armstrong model is successfully used to describe the dynamic flowing behavior of the PM TiAl intermetallics. In general, the PM TiAl intermetallics are found to have promising impact properties, suitable for high-temperature and high-impact applications.展开更多
In order to simulate the microstructure evolution during hot compressive deformation,models of dynamic recrystallization(DRX)by cellular automaton(CA)method for7055aluminum alloy were established.The hot compression t...In order to simulate the microstructure evolution during hot compressive deformation,models of dynamic recrystallization(DRX)by cellular automaton(CA)method for7055aluminum alloy were established.The hot compression tests were conducted toobtain material constants,and models of dislocation density,nucleation rate and recrystallized grain growth were fitted by leastsquare method.The effects of strain,strain rate,deformation temperature and initial grain size on microstructure variation werestudied.The results show that the DRX plays a vital role in grain refinement in hot deformation.Large strain,high temperature andsmall strain rate are beneficial to grain refinement.The stable size of recrystallized grain is not concerned with initial grain size,butdepends on strain rate and temperature.Kinetic characteristic of DRX process was analyzed.By comparison of simulated andexperimental flow stress–strain curves and metallographs,it is found that the established CA models can accurately predict themicrostructure evolution of7055aluminum alloy during hot compressive deformation.展开更多
基金Project(52204084)supported by the National Natural Science Foundation of ChinaProject(FRF-IDRY-GD22-002)supported by the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities),China+2 种基金Project(QNXM20220009)supported by the Fundamental Research Funds for the Central Universities and the Youth Teacher International Exchange and Growth Program,ChinaProjects(2022YFC2905600,2022YFC3004601)supported by the National Key R&D Program of ChinaProject(2023XAGG0061)supported by the Science,Technology&Innovation Project of Xiongan New Area,China。
文摘Metal mineral resources play an indispensable role in the development of the national economy.Dynamic disasters in underground metal mines seriously threaten mining safety,which are major scientific and technological problems to be solved urgently.In this article,the occurrence status and grand challenges of some typical dynamic disasters involving roof falling,spalling,collapse,large deformation,rockburst,surface subsidence,and water inrush in metal mines in China are systematically presented,the characteristics of mining-induced dynamic disasters are analyzed,the examples of dynamic disasters occurring in some metal mines in China are summarized,the occurrence mechanism,monitoring and early warning methods,and prevention and control techniques of these disasters are highlighted,and some new opinions,suggestions,and solutions are proposed simultaneously.Moreover,some shortcomings in current disaster research are pointed out,and the direction of efforts to improve the prevention and control level of dynamic disasters in China’s metal mines in the future is prospected.The integration of forward-looking key innovative theories and technologies in the abovementioned aspects will greatly enhance the cognitive level of disaster prevention and mitigation in China’s metal mining industry and achieve a significant shift from passive disaster relief to active disaster prevention.
基金the financial support presented by Brain Pool Program of Korea and Core Technology R&D Program for the Development of High Performance Eco-friendly Structural Materials funded by the Korean Ministry of Commerce,Industry and Energy(Project No.10020072)2011 Program of Ministry of Education of China
文摘Dislocation mechanism operating in dynamic recrystallization （DRX） during hot compression of Mg-5.51Zn-0.49Zr alloy was investigated by X-ray diffraction, optical microscopy and transmission electron microscopy. The results showed that the continuous DRX occurred at a low strain rate of 1×10^-3s^-1, which was associated with the operation of the single gliding dislocation climbing. At the intermediate strain rate of 1×10^-2s^-1, the continuous DRX was associated with the climbing of the gliding dislocation array as deformed at an elevated temperature of 350 ℃, and in contrast, the discontinuous DRX was observed and associated with the bulging of subgrain boundaries as the deformation temperature was raised to 400 ℃. The continuous DRX was associated with the climbing of the leading dislocation ahead of pile-ups, and resultant rearrangement of misorientated flat dislocation pile-ups as the strain rate was increased to 1×100s^-1. It is suggested that the mechanism predominating the dislocation climbing was changed from the vacancy migration to the stress acting on the leading dislocation ahead of the pile-up as the strain rate was gradually increased.
基金Project (50804015) supported by the National Natural Science Foundation of ChinaProject (GJJ11162) supported by the Youth Science Foundation of Jiangxi Educational Committee,ChinaProject (EA201001035) supported by the Doctor Startup Foundation of Nanchang Hangkong University,China
文摘The flow stress behavior of extruded AZ31 magnesium alloy sheet was investigated by means of compression tests at temperatures between 473 and 523 K and strain rates ranging from 0.001 to 1.0 s-1. The deformation activation energy of the sheet in extrusion direction （ED） was calculated, and the relationship between the softening effect and deformation mechanism was elucidated by optical microscopy and transmission electron microscopy. The results show that when the extruded AZ31 magnesium alloy samples were compressed at moderate temperatures in ED direction, the deformation activation energy is 174.18 kJ/mol, which means that dynamic recrystallization （DRX） is the main softening effect and is controlled by cross slip of thermal active dislocation. Dislocation slip is the main deformation mechanism in moderate-temperature deformation process except twinning. The main DRX effect at moderate temperatures can be considered to be continuous dynamic recrystallization accommodated with twinning DRX.
基金Projects(51261020,51164030)supported by the National Natural Science Foundation of ChinaProject(GF201401007)supported by the Open Fund of National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology,China
文摘Dynamic recrystallization (DRX) behavior in β phase region for the burn resistant titanium alloy Ti?25V?15Cr?0.2Si was investigated with a compression test in the temperature range of 950?1100 °C and the strain rate of 0.001?1 s?1. The results show that deformation mechanism of this alloy in hot deformation is dominated by DRX, and new grains of DRX are evolved by bulging nucleation mechanism as a predominant mechanism. DRX occurs more easily with the decrease of strain rate and the increase of deformation temperature. Grain refinement is achieved due to DRX during the hot deformation at strain rate range of 0.01?0.1 s?1 and temperature range of 950?1050 °C. DRX grain coarsening is observed for the alloy deformed at the higher temperatures of 1100 °C and the lower strain rates of 0.001 s?1. Finally, in order to determine the recrystallized fraction and DRX grain size under different deformation conditions, the prediction models of recrystallization kinetics and recrystallized grain sizes were established.
基金Projects(51475120,U1537201) supported by the National Natural Science Foundation of China
文摘The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.
基金Project(51774335)supported by the National Natural Science Foundation of ChinaProject(2017JJ2311)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(KFJJ11-7M)supported by the Opening Project of State Key Laboratory of Explosion Science and Technology,ChinaProject(HKHTZD20140702020004)supported by the Special Funds for Future Industrial Development of Shenzhen City,China
文摘Split Hopkinson Tension Bar(SHTB) experiments were conducted to explore the dynamic mechanical behavior and deformation mechanism of powder metallurgical(PM) Ti-47 Al-2 Nb-2 Cr-0.2 W(at.%)intermetallics with near lamellar(NL) and duplex(DP)microstructures. Results show that,under dynamic loading,the high temperature strength of the PM TiAl intermetallics is higher than that under quasi-static loading, and the ductile to brittle transition temperature(DBTT) increases with the increase of strain rate. Formation of twinning and stacking faults is the main deformation mechanism during dynamic loading. The work hardening rates of the PM TiAl intermetallics are nearly insensitive to strain rate and temperature at high strain rates(800-1600 s-1)and high temperatures(650-850 ℃). Zerilli-Armstrong model is successfully used to describe the dynamic flowing behavior of the PM TiAl intermetallics. In general, the PM TiAl intermetallics are found to have promising impact properties, suitable for high-temperature and high-impact applications.
基金Projects(51175257,51405520) supported by the National Natural Science Foundation of China
文摘In order to simulate the microstructure evolution during hot compressive deformation,models of dynamic recrystallization(DRX)by cellular automaton(CA)method for7055aluminum alloy were established.The hot compression tests were conducted toobtain material constants,and models of dislocation density,nucleation rate and recrystallized grain growth were fitted by leastsquare method.The effects of strain,strain rate,deformation temperature and initial grain size on microstructure variation werestudied.The results show that the DRX plays a vital role in grain refinement in hot deformation.Large strain,high temperature andsmall strain rate are beneficial to grain refinement.The stable size of recrystallized grain is not concerned with initial grain size,butdepends on strain rate and temperature.Kinetic characteristic of DRX process was analyzed.By comparison of simulated andexperimental flow stress–strain curves and metallographs,it is found that the established CA models can accurately predict themicrostructure evolution of7055aluminum alloy during hot compressive deformation.
