The hot deformation behavior of Ti22A125 Nb was investigated by hot compression test.The flow stressstrain curves can be divided into two types：conventional dynamic recrystallization（DRX） and discontinuous DRX.The ...The hot deformation behavior of Ti22A125 Nb was investigated by hot compression test.The flow stressstrain curves can be divided into two types：conventional dynamic recrystallization（DRX） and discontinuous DRX.The different softening mechanism and micro structure observation of conventional DRX and discontinuous DRX were analyzed.The processing map（PM） of Ti22A125 Nb was built to predict the safe deformation region.The optimal low strain rate domain（DOM I） with high power dissipation efficiency indicates the complete DRX.Additionally,in the high strain rate and low-temperature domain（DOM Ⅲ）,the power dissipation efficiency is low and some adiabatic shear bands and glide bands are observed,which are unsafe and should be avoided.Finally,the DRX map was established.In DOM I,it reveals low dislocation density and high DRX content,which is in agreement with PM.展开更多
The isothermally compression deformation behavior of an elevated Cu/Li weight ratio Al–Cu–Li alloy was investigated under various deformation conditions.The isothermal compression tests were carried out in a tempera...The isothermally compression deformation behavior of an elevated Cu/Li weight ratio Al–Cu–Li alloy was investigated under various deformation conditions.The isothermal compression tests were carried out in a temperature range from 300 to 500℃ and at a strain rate range from 0.001 to 10 s^-1.The results show that the peak stress level decreases with temperature increasing and strain rate decreasing,which is represented by the Zener–Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of 218.5 k J/mol.At low Z value,the dynamic recrystallized grain is well formed with clean high-angle boundaries.At high Z value,a high dislocation density with poorly developed cellularity and considerable fine dynamic precipitates are observed.Based on the experimental data and dynamic material model,the processing maps at strain of 0.3,0.5 and 0.7 were developed to demonstrate the hot workability of the alloy.The results show that the main softening mechanism at high Z value is precipitate coarsening and dynamic recovery;the dynamic recrystallization of the alloy can be easily observed as ln Z ≤ 29.44,with peak efficiency of power dissipation of around 70%.At strains of 0.3,0.5 and 0.7,the flow instability domains are found at higher strain rates,which mainly locate at the upper part of processing maps.In addition,when the strain rate is 0.001 or 0.02 s^-1,there is a particular instability domain at 300–350℃.展开更多
The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator....The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.展开更多
Equipment has dual nature: physical objects existing in nature, and artificial objects designed by human. The decision on the configuration and structural parameters of equipment is made by engineers based on technica...Equipment has dual nature: physical objects existing in nature, and artificial objects designed by human. The decision on the configuration and structural parameters of equipment is made by engineers based on technical-physical effects which control the behavioral parameters of the equipment. Sensors are mounted on the equipment to monitor the equipment state. Current methods for state monitoring and diagnosis mostly use mathematics and artificial intelligence technology to construct evaluation methods. This paper presents an integrated design and state maintenance method, in which graph and dual graph are used for recording design data and sensor arrangement and for mapping method from signals to substructures and connection pairs. An example of state maintenance of hydro power generating equipment is illustrated.展开更多
This article introduces the concept of commutative semigroups of almost asymptotically nonexpansive-type mappings in a Banach space X which has the Opial property and whose norm is UKK, and establishes the weak conver...This article introduces the concept of commutative semigroups of almost asymptotically nonexpansive-type mappings in a Banach space X which has the Opial property and whose norm is UKK, and establishes the weak convergence theorems for almostorbits of this class of commutative semigroups. The author improves, extends and develops some recent and earlier results.展开更多
Hot deformation behavior of the Cu-Cr-Zr alloy was investigated using hot compressive tests in the tem- perature range of 650-850℃ and strain rate range of 0.001-10 s-1. The constitutive equation of the alloy based o...Hot deformation behavior of the Cu-Cr-Zr alloy was investigated using hot compressive tests in the tem- perature range of 650-850℃ and strain rate range of 0.001-10 s-1. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of strain rate and deformation temperature. The critical conditions for the occurrence of dynamic recrystallization were determined based on the alloy strain hardening rate curves. Based on the dynamic material model, the processing maps at the strains of 0.3, 0.4 and 0.5 were obtained. When the true strain was 0.5, greater power dissipation efficiency was observed at 800-850 ℃ and under 0.001-0.1 s-1, with the peak efficiency of 47%. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Based on the processing maps and microstructure evolution, the optimal hot working conditions for the Cu-Cr-Zr alloy are in the temperature range of 800-850 ℃ and the strain rate range of 0.001-0.1 s-1.展开更多
The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the unia...The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the uniaxial compression tests. The results showed that the high temperature deformation behaviors were highly sensitive to strain rate and temperature, and the flow stress decreased with the increase of temperature, as well as with the decrease of strain rate. Additionally, the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass displayed smaller flow stress under the same condition. The flow behavior changed from Newtonian to non-Newtonian with increase of the strain rate, as well as the decrease of temperature, which could be explained by the transition state theory. We found that（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass had better flow behavior than the Cu_（43）Zr_（48）Al_9 bulk metallic glass in the supercooled liquid region. In addition, the processing maps of the two bulk metallic glasses were constructed considering the power dissipation efficiency. The optimum domain for thermal workability of the bulk metallic glass was located using the processing map, where the power dissipation efficiency was larger than 0.8. It was shown that the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass, which had larger area of optimum domain, had excellent thermoplastic forming.展开更多
Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature de...Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this alloy.However, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.展开更多
The deformation behavior and mechanisms of Ti-1023 alloy were studied in the temperature range of 650-900 ℃ and strain rate range of 0.001-10 s-1 by compression and tensile tests. The results show that in a limited s...The deformation behavior and mechanisms of Ti-1023 alloy were studied in the temperature range of 650-900 ℃ and strain rate range of 0.001-10 s-1 by compression and tensile tests. The results show that in a limited strain rate range of 0.001-0.1 s-1, the kinetic rate equation is obeyed and a linear fit is obtained at all the temperatures. The apparent activation energy is 322 kJ/mol in the α-β region and 160 kJ/mol in the β region, respectively. Power dissipation maps of this alloy developed by using Gleeble test data show three domains in the tested range. Superplasticity, marked by abnormal elongation at 700 ℃, occurs in the temperature range of 650-750 ℃ and at strain rates below about 0.03 s-1. Large grain superplasticity takes place in the temperature range of 750-850 ℃ and strain rates range of 0.001-0.03 s-1. Dynamic recrystallization occurs in the temperature range of 850-900 ℃ and at strain rates below about 1 s-1. The instability maps of this alloy were also developed.展开更多
In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strai...In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.展开更多
The hot deformation behavior of Ti 5.6Al-4.8Sn-2.0Zr-1.0Mo 0.35Si 0.85Nd alloy in β/quasi-β forging process was studied using isothermal compression tests over temperature range from 1040℃ to 1 100 ℃ and strain ra...The hot deformation behavior of Ti 5.6Al-4.8Sn-2.0Zr-1.0Mo 0.35Si 0.85Nd alloy in β/quasi-β forging process was studied using isothermal compression tests over temperature range from 1040℃ to 1 100 ℃ and strain rates form 0. 001 s-1 to 70 s -1. The results show that the flow stress and mierostrueture are sensitive to thermomechanical parameters. The processing maps based on the dynamic materials model at strain of 0.3 and 0.7 were established. The optimum deformation thermomechanical parameters at a strain of 0.7 have two regions that exhibit the peak of power dissipation efficiency. One is the region of 1062-1100 ℃ and 10- 3 10-1.5 s -1 ; and another which represents dynamic recrystallization is 1040-1045 ℃ and 10-1.8 10- 0.5 s -1. The instable region is located where the strain rate is larger than 1 s 1 which corresponds to the mechanical instability.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51175431)
文摘The hot deformation behavior of Ti22A125 Nb was investigated by hot compression test.The flow stressstrain curves can be divided into two types：conventional dynamic recrystallization（DRX） and discontinuous DRX.The different softening mechanism and micro structure observation of conventional DRX and discontinuous DRX were analyzed.The processing map（PM） of Ti22A125 Nb was built to predict the safe deformation region.The optimal low strain rate domain（DOM I） with high power dissipation efficiency indicates the complete DRX.Additionally,in the high strain rate and low-temperature domain（DOM Ⅲ）,the power dissipation efficiency is low and some adiabatic shear bands and glide bands are observed,which are unsafe and should be avoided.Finally,the DRX map was established.In DOM I,it reveals low dislocation density and high DRX content,which is in agreement with PM.
基金supported by the Foundation for Science and Technology Development Project of Shandong (No.2014GGX102006)
文摘The isothermally compression deformation behavior of an elevated Cu/Li weight ratio Al–Cu–Li alloy was investigated under various deformation conditions.The isothermal compression tests were carried out in a temperature range from 300 to 500℃ and at a strain rate range from 0.001 to 10 s^-1.The results show that the peak stress level decreases with temperature increasing and strain rate decreasing,which is represented by the Zener–Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of 218.5 k J/mol.At low Z value,the dynamic recrystallized grain is well formed with clean high-angle boundaries.At high Z value,a high dislocation density with poorly developed cellularity and considerable fine dynamic precipitates are observed.Based on the experimental data and dynamic material model,the processing maps at strain of 0.3,0.5 and 0.7 were developed to demonstrate the hot workability of the alloy.The results show that the main softening mechanism at high Z value is precipitate coarsening and dynamic recovery;the dynamic recrystallization of the alloy can be easily observed as ln Z ≤ 29.44,with peak efficiency of power dissipation of around 70%.At strains of 0.3,0.5 and 0.7,the flow instability domains are found at higher strain rates,which mainly locate at the upper part of processing maps.In addition,when the strain rate is 0.001 or 0.02 s^-1,there is a particular instability domain at 300–350℃.
基金the National Basic Research Program of China(No.2005CB623705)
文摘The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.
基金the National Natural Science Foundation of China(No.51175284)
文摘Equipment has dual nature: physical objects existing in nature, and artificial objects designed by human. The decision on the configuration and structural parameters of equipment is made by engineers based on technical-physical effects which control the behavioral parameters of the equipment. Sensors are mounted on the equipment to monitor the equipment state. Current methods for state monitoring and diagnosis mostly use mathematics and artificial intelligence technology to construct evaluation methods. This paper presents an integrated design and state maintenance method, in which graph and dual graph are used for recording design data and sensor arrangement and for mapping method from signals to substructures and connection pairs. An example of state maintenance of hydro power generating equipment is illustrated.
基金Project supported by the Teaching and Research Award Fund for Outstanding Young Teachers in Higher Education Institutions of MOE,P.R.C., by the Dawn Program Foundation in Shanghai, and by Shanghai Leading Academic Discipline Project Fund (T0401).
文摘This article introduces the concept of commutative semigroups of almost asymptotically nonexpansive-type mappings in a Banach space X which has the Opial property and whose norm is UKK, and establishes the weak convergence theorems for almostorbits of this class of commutative semigroups. The author improves, extends and develops some recent and earlier results.
基金financially supported by the National Natural Science Foundation of China(No.51101052)the National Science Foundation(No.IRES 1358088)
文摘Hot deformation behavior of the Cu-Cr-Zr alloy was investigated using hot compressive tests in the tem- perature range of 650-850℃ and strain rate range of 0.001-10 s-1. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of strain rate and deformation temperature. The critical conditions for the occurrence of dynamic recrystallization were determined based on the alloy strain hardening rate curves. Based on the dynamic material model, the processing maps at the strains of 0.3, 0.4 and 0.5 were obtained. When the true strain was 0.5, greater power dissipation efficiency was observed at 800-850 ℃ and under 0.001-0.1 s-1, with the peak efficiency of 47%. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Based on the processing maps and microstructure evolution, the optimal hot working conditions for the Cu-Cr-Zr alloy are in the temperature range of 800-850 ℃ and the strain rate range of 0.001-0.1 s-1.
基金supported by the Education Department of Shaanxi Province(14JK1351)the Principal Fund of Xi’an Technological University(0852-302021407)
文摘The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the uniaxial compression tests. The results showed that the high temperature deformation behaviors were highly sensitive to strain rate and temperature, and the flow stress decreased with the increase of temperature, as well as with the decrease of strain rate. Additionally, the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass displayed smaller flow stress under the same condition. The flow behavior changed from Newtonian to non-Newtonian with increase of the strain rate, as well as the decrease of temperature, which could be explained by the transition state theory. We found that（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass had better flow behavior than the Cu_（43）Zr_（48）Al_9 bulk metallic glass in the supercooled liquid region. In addition, the processing maps of the two bulk metallic glasses were constructed considering the power dissipation efficiency. The optimum domain for thermal workability of the bulk metallic glass was located using the processing map, where the power dissipation efficiency was larger than 0.8. It was shown that the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass, which had larger area of optimum domain, had excellent thermoplastic forming.
基金financially supported by the Project of Introducing Talents of Discipline to Universities‘‘111’’Project(No.B08040)
文摘Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this alloy.However, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.
文摘The deformation behavior and mechanisms of Ti-1023 alloy were studied in the temperature range of 650-900 ℃ and strain rate range of 0.001-10 s-1 by compression and tensile tests. The results show that in a limited strain rate range of 0.001-0.1 s-1, the kinetic rate equation is obeyed and a linear fit is obtained at all the temperatures. The apparent activation energy is 322 kJ/mol in the α-β region and 160 kJ/mol in the β region, respectively. Power dissipation maps of this alloy developed by using Gleeble test data show three domains in the tested range. Superplasticity, marked by abnormal elongation at 700 ℃, occurs in the temperature range of 650-750 ℃ and at strain rates below about 0.03 s-1. Large grain superplasticity takes place in the temperature range of 750-850 ℃ and strain rates range of 0.001-0.03 s-1. Dynamic recrystallization occurs in the temperature range of 850-900 ℃ and at strain rates below about 1 s-1. The instability maps of this alloy were also developed.
基金financially supported by the National Natural Science Foundation of China (Nos. 81071262, 31271024 and 31470930)the Funding from Northeastern University ("985 program", Nos. N141008001 and LZ2014018), China
文摘In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.
基金Item Sponsored by National Natural Science Foundation of China(51164030,51261020)Education Commission Foundation of Jiangxi Province of China(GJJ13501)
文摘The hot deformation behavior of Ti 5.6Al-4.8Sn-2.0Zr-1.0Mo 0.35Si 0.85Nd alloy in β/quasi-β forging process was studied using isothermal compression tests over temperature range from 1040℃ to 1 100 ℃ and strain rates form 0. 001 s-1 to 70 s -1. The results show that the flow stress and mierostrueture are sensitive to thermomechanical parameters. The processing maps based on the dynamic materials model at strain of 0.3 and 0.7 were established. The optimum deformation thermomechanical parameters at a strain of 0.7 have two regions that exhibit the peak of power dissipation efficiency. One is the region of 1062-1100 ℃ and 10- 3 10-1.5 s -1 ; and another which represents dynamic recrystallization is 1040-1045 ℃ and 10-1.8 10- 0.5 s -1. The instable region is located where the strain rate is larger than 1 s 1 which corresponds to the mechanical instability.
