Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250...Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.展开更多
The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior we...The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior were investigated,and the flow stress-strain error caused by friction was revised.The results showed that the effect of the friction was obvious with increasing strain rate and decreasing deformation temperature.The revised flow stress is decreased by increasing temperature and decreasing strain rate and exhibits a typical dynamic recrystallization behavior.The constitutive model has been developed through a hyperbolic-sine Arrhenius type equation to relate the flow stress,strain rate and temperature.The influence of strain has also been incorporated by considering the variation of material constants as a function of strain.The prediction accuracy of developed constitutive model has been assessed using standard statistical formulae.According to the analysis results,the proposed deformation constitutive equation gives an accurate and precise estimate of flow stress of delta-processed Inconel 718 alloy.展开更多
Hot deformation behavior of an as-extruded duplex structured Mg-9Li-3Al-2.5Sr alloy is investigated via hot compression tests conducted at 200-350℃ with strain rate of 0.001-1 s^-1.The flow behavior of Mg-9Li-3Al-2.5...Hot deformation behavior of an as-extruded duplex structured Mg-9Li-3Al-2.5Sr alloy is investigated via hot compression tests conducted at 200-350℃ with strain rate of 0.001-1 s^-1.The flow behavior of Mg-9Li-3Al-2.5Sr alloy can be described accurately by hyperbolic sine constitutive equation and the average activation energy for deformation is calculated as 143.5 k J/mol.Based on a dynamic materials model,the processing maps of Mg-9Li-3Al-2.5Sr alloy which describe the variation of power dissipation efficiency are constructed as a function of temperature and strain rate.The processing maps exhibit an area of discontinuous dynamic recrystallization occurring at 280-300℃ with strain rate of 0.001-0.01 s^-1,which corresponds to the optimum hot working conditions.展开更多
基金supported by the Major State Basic Research Development Program of China (No.2011CB012900)the National Natural Science Foundation of China (No.51374144)the Shanghai Rising-Star Program (No.14QA1402300)
文摘Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.
基金Sponsored by National High Technology Research and Development Program of China(2012AA03A514)Youth Scientific Research Foundation of Central South University of Forestry and Technology of China(QJ2010001A)
文摘The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1 060℃ and strain rate range of 0.001-0.5s-1.The effects of friction and temperature on the compressive deformation behavior were investigated,and the flow stress-strain error caused by friction was revised.The results showed that the effect of the friction was obvious with increasing strain rate and decreasing deformation temperature.The revised flow stress is decreased by increasing temperature and decreasing strain rate and exhibits a typical dynamic recrystallization behavior.The constitutive model has been developed through a hyperbolic-sine Arrhenius type equation to relate the flow stress,strain rate and temperature.The influence of strain has also been incorporated by considering the variation of material constants as a function of strain.The prediction accuracy of developed constitutive model has been assessed using standard statistical formulae.According to the analysis results,the proposed deformation constitutive equation gives an accurate and precise estimate of flow stress of delta-processed Inconel 718 alloy.
基金the financial support from the National Natural Science Foundation(Project No.51601024)the National Key Research and Development plan(Project No.2016YFB0700403)+1 种基金the Chongqing Research Program of Basic Research and Frontier Technology(Project No.cstc2016jcyj A0418)the Fundamental Research Funds for the Central Universities(Project No.106112015CDJXY130011 and No.CDJZR14130007)
文摘Hot deformation behavior of an as-extruded duplex structured Mg-9Li-3Al-2.5Sr alloy is investigated via hot compression tests conducted at 200-350℃ with strain rate of 0.001-1 s^-1.The flow behavior of Mg-9Li-3Al-2.5Sr alloy can be described accurately by hyperbolic sine constitutive equation and the average activation energy for deformation is calculated as 143.5 k J/mol.Based on a dynamic materials model,the processing maps of Mg-9Li-3Al-2.5Sr alloy which describe the variation of power dissipation efficiency are constructed as a function of temperature and strain rate.The processing maps exhibit an area of discontinuous dynamic recrystallization occurring at 280-300℃ with strain rate of 0.001-0.01 s^-1,which corresponds to the optimum hot working conditions.
