The hot deformation characteristics of induction quenched Zr-Sn-Nb-Fe-Cr alloy forged rod in the temperature range of 600–900°C and strain rate range of 0.001–1 s^(-1)were studied by Gleeble3800 uniaxial hot co...The hot deformation characteristics of induction quenched Zr-Sn-Nb-Fe-Cr alloy forged rod in the temperature range of 600–900°C and strain rate range of 0.001–1 s^(-1)were studied by Gleeble3800 uniaxial hot compression experiment.The results show that the flow stress decreases with the decrease in strain rate and the increase in deformation temperature in the true stress-true strain curve of Zr-Sn-Nb-Fe-Cr alloy forged rod.Moreover,the hot deformation characteristics of the material can be described by the hyperbolic sine constitutive equation.Under the experimental conditions,the average thermal activation energy(Q)of the alloy was 412.9105 kJ/mol.The microstructure analysis of the processing map and the sample after hot compression shows that the optimum hot working parameters of the alloy are 795–900°C,0.001–0.0068 s^(-1),at the deformation temperature of 600–900°C,and the strain rate of 0.001–1 s^(-1).展开更多
This study systematically investigates the hot deformation behavior and microstructural evolution of CoNiV medium-entropy alloy(MEA)in the temperature range of 950-1100℃ and strain rates of 0.001-1 s^(-1).The Arrheni...This study systematically investigates the hot deformation behavior and microstructural evolution of CoNiV medium-entropy alloy(MEA)in the temperature range of 950-1100℃ and strain rates of 0.001-1 s^(-1).The Arrhenius model and machine learning model were developed to forecast flow stresses at various conditions.The predictive capability of both models was assessed using the coefficients of determination(R^(2)),average absolute relative error(AARE),and root mean square error(RMSE).The findings show that the osprey optimization algorithm convolutional neural network(OOA-CNN)model outperforms the Arrhenius model,achieving a high R^(2) value of 0.99959 and lower AARE and RMSE values.The flow stress that the OOA-CNN model predicted was used to generate power dissipation maps and instability maps under different strains.Finally,combining the processing map and microstructure characterization,the ideal processing domain was identified as 1100℃ at strain rates of 0.01-0.1 s^(-1).This study provided key insights into optimizing the hot working process of CoNiV MEA.展开更多
Ti750s titanium alloy,a novel high-temperature titanium alloy designed for short-term service at elevated temperatures(700–750℃),has previously lacked comprehensive understanding of its hot processing behavior.In th...Ti750s titanium alloy,a novel high-temperature titanium alloy designed for short-term service at elevated temperatures(700–750℃),has previously lacked comprehensive understanding of its hot processing behavior.In this study,the high-temperature deformation behavior and microstructural evolution of the Ti750s alloy were systematically investigated through thermal simulation compression tests conducted at temperatures ranging from 900 to 1070℃and strain rates between 0.1 and 10 s⁻1.A hot processing map was constructed using the dynamic material model to optimize the hot processing parameters.The results indicated that the optimal processing window was between 1040 and 1070℃with a strain rate of 0.1 s⁻1.Processing within the instability region resulted in localized plastic deformation,manifesting as pronounced shear bands and a highly heterogeneous strain distribution;this region should be avoided during hot deformation.Within theα+βphase safety zone characterized by low power dissipation rates between 0.32 and 0.4,the primary deformation mechanism in this region was dynamic recovery(DRV),where the lamellarαgrains underwent deformation and rotation.Conversely,in theα+βphase safety zone with high-power dissipation rates between 0.45 and 0.52,dynamic spheroidization of theαphase and dynamic recrystallization(DRX)of theβphase occurred concurrently.In theβphase safety zone with low power dissipation rates between 0.32 and 0.51,the primary deformation mechanism consisted of DRV ofβgrains,accompanied by limited DRX.However,in theβphase safety zone with high-power dissipation rates exceeding 0.56,both DRV and DRX ofβgrains took place,resulted in a significant increase in the size and number of recrystallized grains compared to those observed under low power dissipation conditions.展开更多
The current study investigates the hot deformation behavior of Al-12Ce-0.4Sc alloy with an isothermal hot compression test at300-450°C/0.001-1s^(-1).Results show that the flow curves exhibit typical dynamic recov...The current study investigates the hot deformation behavior of Al-12Ce-0.4Sc alloy with an isothermal hot compression test at300-450°C/0.001-1s^(-1).Results show that the flow curves exhibit typical dynamic recovery(DRV)and slight flow-softening behavior.Additionally,the flow curves overlap owing to the dynamic strain aging(DSA)phenomenon at 400-450°C/0.01-0.1 s^(-1).Two different constitutive models were developed using the experimental data for hot deformation:(i)strain-compensated Arrhenius model(Method I)and(ii)logistic regression model(MethodⅡ).The average stress exponent(n)and apparent activation energy(Q)are 14.25 and 209.58 k J·mol^(-1),respectively.The hot-working processing map shows that the optimal processing condition is 400°C/1 s^(-1),and the maximum power dissipation efficiency is 22%.Stable and unstable domains indicated by the processing map were correlated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),and electron backscatter diffraction(EBSD)characterization techniques.The unstable domains are primarily associated with pro-eutectic Al11Ce3intermetallic fracture and interfacial cracks betweenα-Al and pro-eutectic Al_(11)Ce_(3).展开更多
Hot deformation behavior of extrusion preform of the spray-formed Al-9.0Mg-0.5Mn-0.1Ti alloy was studied using hot compression tests over deformation temperature range of 300-450 ℃ and strain rate range of 0.01...Hot deformation behavior of extrusion preform of the spray-formed Al-9.0Mg-0.5Mn-0.1Ti alloy was studied using hot compression tests over deformation temperature range of 300-450 ℃ and strain rate range of 0.01-10 s-1. On the basis of experiments and dynamic material model, 2D processing maps and 3D power dissipation maps were developed for identification of exact instability regions and optimization of hot processing parameters. The experimental results indicated that the efficiency factor of energy dissipate （η） lowered to the minimum value when the deformation conditions located at the strain of 0.4, temperature of 300 ° C and strain rate of 1 s-1. The softening mechanism was dynamic recovery, the grain shape was mainly flat, and the portion of high angle grain boundary （〉15°） was 34%. While increasing the deformation temperature to 400 ° C and decreasing the strain rate to 0.1 s-1, a maximum value of η was obtained. It can be found that the main softening mechanism was dynamic recrystallization, the structures were completely recrystallized, and the portion of high angle grain boundary accounted for 86.5%. According to 2D processing maps and 3D power dissipation maps, the optimum processing conditions for the extrusion preform of the spray-formed Al？9.0Mg？0.5Mn？0.1Ti alloy were in the deformation temperature range of 340-450 ° C and the strain rate range of 0.01-0.1 s-1 with the power dissipation efficiency range of 38%？43%.展开更多
The high-temperature deformation behavior of Cu-Ni-Si-P alloy was investigated by using the hot compression test in the temperature range of 600-800 ℃ and strain rate of 0.01-5 s-1. The hot deformation activation ene...The high-temperature deformation behavior of Cu-Ni-Si-P alloy was investigated by using the hot compression test in the temperature range of 600-800 ℃ and strain rate of 0.01-5 s-1. The hot deformation activation energy, Q, was calculated and the hot compression constitutive equation was established. The processing maps of the alloy were constructed based on the experiment data and the forging process parameters were then optimized based on the generated maps for forging process determination. The flow behavior and the microstructural mechanism of the alloy were studied. The flow stress of the Cu-Ni-Si-P alloy increases with increasing strain rate and decreasing deformation temperature, and the dynamic recrystallization temperature of alloy is around 700 ℃. The hot deformation activation energy for dynamic recrystallization is determined as 485.6 kJ/mol. The processing maps for the alloy obtained at strains of 0.3 and 0.5 were used to predict the instability regimes occurring at the strain rate more than 1 s-1 and low temperature （〈650 ℃）. The optimum range for the alloy hot deformation processing in the safe domain obtained from the processing map is 750-800 ℃ at the strain rate of 0.01-0.1 s i The characteristic microstructures predicted from the processing map agree well with the results of microstructural observations.展开更多
High temperature compressive deformation behaviors of as-cast Ti-43Al-4Nb-1.4W-0.6B alloy was investigated at temperatures ranging from 1323 K to 1473 K, and strain rates from 0.001 s-1 to 1 s-1. The results indicated...High temperature compressive deformation behaviors of as-cast Ti-43Al-4Nb-1.4W-0.6B alloy was investigated at temperatures ranging from 1323 K to 1473 K, and strain rates from 0.001 s-1 to 1 s-1. The results indicated that the true stress-true strain curves show a dynamic flow softening behavior. The flow curves after the friction and the temperature compensations were employed to develop constitutive equations. The effects of temperature and the strain rate on the deformation behavior were represented by Zener-Holloman exponential equation. The influence of strain was incorporated in the constitutive analysis by considering the effect of the strain on material constants by a five-order polynomial. A revised model was proposed to describe the relationships among the flow stress, strain rate and temperature and the predicted flow stress curves were in good agreement with experimental results. Appropriate deformation processing parameters were suggested based on the processing map which was constructed from friction and temperature corrected flow curves, determined as 1343 K, 0.02 s-1 and were successfully applied in the canned forging of billets to simulate industrial work condition.展开更多
Hot compression test of a novel nickel-free white alloy Cu?12Mn?15Zn?1.5Al?0.3Ti?0.14B?0.1Ce (mass fraction, %) was conducted on a Gleeble?1500 machine in the temperature range of 600?800 °C and the strain rate r...Hot compression test of a novel nickel-free white alloy Cu?12Mn?15Zn?1.5Al?0.3Ti?0.14B?0.1Ce (mass fraction, %) was conducted on a Gleeble?1500 machine in the temperature range of 600?800 °C and the strain rate range of 0.01?10 s?1. The constitutive equation and hot processing map of the alloy were built up according to its hot deformation behavior and hot working characteristics. The deformation activation energy of the alloy is 203.005 kJ/mol. An instability region appears in the hot deformation temperature of 600?700 °C and the strain rate range of 0.32?10 s?1 when the true strain of the alloy is up to 0.7. Under the optimal hot deformation condition of 800 °C and 10 s?1 the prepared specimen has good surface quality and interior structure. The designed nickel-free alloy has very similar white chromaticity with the traditional white copper alloy (Cu?15Ni?24Zn?1.5Pb), and the color difference between them is less than 1.5, which can hardly be distinguished by human eyes.展开更多
The deformation behaviors of a new quaternary Mg-6Zn-1.5Cu-0.5Zr alloy at temperatures of 523-673 K and strain rates of 0.001-1 s-1 were studied by compressive tests using a Gleeble 3800 thermal-simulator.The results ...The deformation behaviors of a new quaternary Mg-6Zn-1.5Cu-0.5Zr alloy at temperatures of 523-673 K and strain rates of 0.001-1 s-1 were studied by compressive tests using a Gleeble 3800 thermal-simulator.The results show that the flow stress increases as the deformation temperature decreases or as the strain rate increases.A strain-dependent constitutive equation and a feed-forward back-propagation artificial neural network were used to predict flow stress,which showed good agreement with experimental data.The processing map suggests that the domains of 643-673 K and 0.001-0.01 s-1 are corresponded to optimum conditions for hot working of the T4-treated Mg-6Zn-1.5Cu-0.5Zr alloy.展开更多
The flow stress features of PM Ti-47Al-2Cr-0.2Mo alloy were studied by isothermal compression in the temperature range from 1000 to 1150 °C with strain rates of 0.001-1 s-1 on Gleeble-1500 thermo-simulation machi...The flow stress features of PM Ti-47Al-2Cr-0.2Mo alloy were studied by isothermal compression in the temperature range from 1000 to 1150 °C with strain rates of 0.001-1 s-1 on Gleeble-1500 thermo-simulation machine.The results show that the deformation temperature and strain rate have obvious effects on the flow characteristic,and the flow stress increases with increasing strain rate and decreasing temperature.The processing maps under different deformation conditions were established.The processing maps of this alloy are sensitive to strains.The processing map at the strain of 0.5 exhibits two suitable deformation domains of 1000-1050 °C at 0.001-0.05 s-1 and 1050-1125 °C at 0.01-0.1 s-1.The optimum parameters for hot working of the alloy are deformation temperature of 1000 °C and strain rate of 0.001 s-1 according to the processing map and microstructure at true strain of 0.5.展开更多
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GE...Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79.展开更多
Based on the experimental data of Ti40 alloy obtained from Gleeble-1500 thermal simulator,an artificial neural network model of high temperature flow stress as a function of strain,strain rate and temperature was esta...Based on the experimental data of Ti40 alloy obtained from Gleeble-1500 thermal simulator,an artificial neural network model of high temperature flow stress as a function of strain,strain rate and temperature was established.In the network model,the input parameters of the model are strain,logarithm strain rate and temperature while flow stress is the output parameter.Multilayer perceptron（MLP） architecture with back-propagation algorithm is utilized.The present study achieves a good performance of the artificial neural network（ANN） model,and the predicted results are in agreement with experimental values.A processing map of Ti40 alloy is obtained with the flow stress predicted by the trained neural network model.The processing map developed by ANN model can efficiently track dynamic recrystallization and flow localization regions of Ti40 alloy during deforming.Subsequently,the safe and instable domains of hot working of Ti40 alloy are identified and validated through microstructural investigations.展开更多
The plastic flow behavior of a newly developed high ductility magnesium alloy, Mg-4Al-2Sn-Y-Nd, was investigated by hot compression from 200 to 400 ℃ with a strain rate of 1.5×10-3 to 7.5 s-1. The results reveal...The plastic flow behavior of a newly developed high ductility magnesium alloy, Mg-4Al-2Sn-Y-Nd, was investigated by hot compression from 200 to 400 ℃ with a strain rate of 1.5×10-3 to 7.5 s-1. The results reveal that the strain rate sensitivity factor （m） of the alloy is much lower than that of the AZ31 alloy, which implies that the alloy should be more suitable for processing at high strain rate. The constitutive relationship of the alloy deformed at elevated temperature was obtained by plotting the experimental data. The stress exponent of the alloy is 10.33, which reveals that climb-controlled dislocations creep is the dominated deformation mechanism. The processing-map technique was used to determine the practical processing window. The proper deformation temperature and strain rate of the cast alloy were determined as 350-400 ℃ and 0.01-0.03 s-1, respectively.展开更多
Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300?550 °C and str...Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300?550 °C and strain rate range of 0.001? 10 s?1 with Gleeble?3500 thermal simulator system. Processing maps of the CNTs/Al alloy at different strains were calculated to study the optimum processing domain. Microstructures before and after hot compressions were characterized by electron backscattered diffraction (EBSD) method. Stress?strain curves indicate that the flow stress increases with the increase of strain rate and the decrease of temperature. The processing maps of the CNTs/Al alloy at different strains show that the optimum processing domain is 500?550 °C, 10 s?1 for hot working. EBSD analysis demonstrates that fully dynamic recrystallization occurs in the optimum processing domain (high strainrate 10 s?1), whereas the main soften mechanism is dynamic recovery at low strain rate (0.001 s?1).展开更多
The three-dimensional （3D） processing maps considering strain based on the two-dimensional （2D） processing maps proposed by PRASAD can describe the distribution of the efficiency of power dissipation and flow inst...The three-dimensional （3D） processing maps considering strain based on the two-dimensional （2D） processing maps proposed by PRASAD can describe the distribution of the efficiency of power dissipation and flow instability regions at various temperatures, strain rates and strains, which exhibit intrinsic workability related to material itself. Finite element （FE） simulation can obtain the distribution of strain, strain rate, temperature and die filling status, which indicates state-of-stress （SOS） workability decided by die shape and different processing conditions. On the basis of this, a new material driven analysis method for hot deformation was put forward by the combination of FE simulation with 3D processing maps, which can demonstrate material workability of the entire hot deformation process including SOS workability and intrinsic workability. The hot forging process for hard-to-work metal magnesium alloy was studied, and the 3D thermomechanical FE simulation including 3D processing maps of complex hot forging spur bevel gear was first conducted. The hot forging experiments were carried out. The results show that the new method is reasonable and suitable to determine the aoorooriate nrocess narameters.展开更多
The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300-450 °C and strain rates of 0.001-1.0 s-1 with Gleeble-1500 D thermal simulator system. The r...The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300-450 °C and strain rates of 0.001-1.0 s-1 with Gleeble-1500 D thermal simulator system. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The hyperbolic sine constitutive equation can describe the flow stress behavior of Al2O3/Al composites, and the deformation activation energy and constitutive equations were calculated. The processing maps of Al2O3/Al-2 μm and Al2O3/Al-1 μm composites at strain of 0.6 were obtained and the optimum processing domains are in ranges of 300-330 °C, 0.007-0.03 s-1 and 335-360 °C, 0.015-0.06 s-1 for hot working, respectively. The instability zones of flow behavior can also be recognized by the maps.展开更多
Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and s...Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and strain rates of 0.0003?1.0 s?1. The constitutive equation was established, power dissipation (η) maps and hot processing maps were plotted. The microstructure evolution and dislocation distribution of domains with different values of η in power dissipation maps were also observed. The results show that the flow stress increases with decreasing temperature and increasing strain rate. The activation energy of the spray forming LSHR alloy is 1243.86 kJ/mol. When the value of η is 0.36 at the strain of 0.5, the domain in the processing map shows characteristics of typical dynamic recrystallization (DRX) and low dislocation density. According to the microstructure evolution and processing maps, the optimum processing condition for good hot workability of spray forming LSHR alloy can be summed up as:temperature range 1110?1150 °C; strain rate range 0.01?0.3 s?1.展开更多
The hot deformation behavior of as-cast Mg-8Zn-1Al-0.5Cu-0.5Mn alloy was studied by hot compression tests at temperatures of 200-350 °C and strain rates of 0.001-1 s-1.The results show that the flow stress increa...The hot deformation behavior of as-cast Mg-8Zn-1Al-0.5Cu-0.5Mn alloy was studied by hot compression tests at temperatures of 200-350 °C and strain rates of 0.001-1 s-1.The results show that the flow stress increases significantly with increasing strain rate,and decreases as the temperature increases.The flow stress model based on the regression analysis was developed to predict the flow behavior of Mg-8Zn-1Al-0.5Cu-0.5Mn alloy during the hot compression,and the model shows a good agreement with experimental results.Meanwhile,the processing maps were established according to the dynamic materials model.The processing maps show that the increase of strain enlarges the instability domains,and the alloy shows good hot workability at high temperatures and low strain rates.展开更多
Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and st...Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.展开更多
Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolut...Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.展开更多
文摘The hot deformation characteristics of induction quenched Zr-Sn-Nb-Fe-Cr alloy forged rod in the temperature range of 600–900°C and strain rate range of 0.001–1 s^(-1)were studied by Gleeble3800 uniaxial hot compression experiment.The results show that the flow stress decreases with the decrease in strain rate and the increase in deformation temperature in the true stress-true strain curve of Zr-Sn-Nb-Fe-Cr alloy forged rod.Moreover,the hot deformation characteristics of the material can be described by the hyperbolic sine constitutive equation.Under the experimental conditions,the average thermal activation energy(Q)of the alloy was 412.9105 kJ/mol.The microstructure analysis of the processing map and the sample after hot compression shows that the optimum hot working parameters of the alloy are 795–900°C,0.001–0.0068 s^(-1),at the deformation temperature of 600–900°C,and the strain rate of 0.001–1 s^(-1).
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.51901078)the Central Guidance for Local Scientific and Technological Development Funding Project(Grant No.236Z1003G)+3 种基金the Science and Technology Plan Project of Tangshan City(Grant No.24130207C)the Natural Science Foundation of Hebei Province(Grant No.E2022209070)the High-level Talent Project of Hebei(Grant No.E2019100007)the Open Project Program of Key Laboratory of Ministry of Education for Modern Metallurgy Technology(Grant No.2024YJKF02).
文摘This study systematically investigates the hot deformation behavior and microstructural evolution of CoNiV medium-entropy alloy(MEA)in the temperature range of 950-1100℃ and strain rates of 0.001-1 s^(-1).The Arrhenius model and machine learning model were developed to forecast flow stresses at various conditions.The predictive capability of both models was assessed using the coefficients of determination(R^(2)),average absolute relative error(AARE),and root mean square error(RMSE).The findings show that the osprey optimization algorithm convolutional neural network(OOA-CNN)model outperforms the Arrhenius model,achieving a high R^(2) value of 0.99959 and lower AARE and RMSE values.The flow stress that the OOA-CNN model predicted was used to generate power dissipation maps and instability maps under different strains.Finally,combining the processing map and microstructure characterization,the ideal processing domain was identified as 1100℃ at strain rates of 0.01-0.1 s^(-1).This study provided key insights into optimizing the hot working process of CoNiV MEA.
基金supported by the National basic scientific research projects(JCKY2021204A004)the National Ministries and Commissions Projects(2019-112hbz)the National Natural Science Foundation of China(No.52271113).
文摘Ti750s titanium alloy,a novel high-temperature titanium alloy designed for short-term service at elevated temperatures(700–750℃),has previously lacked comprehensive understanding of its hot processing behavior.In this study,the high-temperature deformation behavior and microstructural evolution of the Ti750s alloy were systematically investigated through thermal simulation compression tests conducted at temperatures ranging from 900 to 1070℃and strain rates between 0.1 and 10 s⁻1.A hot processing map was constructed using the dynamic material model to optimize the hot processing parameters.The results indicated that the optimal processing window was between 1040 and 1070℃with a strain rate of 0.1 s⁻1.Processing within the instability region resulted in localized plastic deformation,manifesting as pronounced shear bands and a highly heterogeneous strain distribution;this region should be avoided during hot deformation.Within theα+βphase safety zone characterized by low power dissipation rates between 0.32 and 0.4,the primary deformation mechanism in this region was dynamic recovery(DRV),where the lamellarαgrains underwent deformation and rotation.Conversely,in theα+βphase safety zone with high-power dissipation rates between 0.45 and 0.52,dynamic spheroidization of theαphase and dynamic recrystallization(DRX)of theβphase occurred concurrently.In theβphase safety zone with low power dissipation rates between 0.32 and 0.51,the primary deformation mechanism consisted of DRV ofβgrains,accompanied by limited DRX.However,in theβphase safety zone with high-power dissipation rates exceeding 0.56,both DRV and DRX ofβgrains took place,resulted in a significant increase in the size and number of recrystallized grains compared to those observed under low power dissipation conditions.
基金financially supported by the Science and Engineering Research Board(SERB),Government of India(No.EEQ/2020/000306)。
文摘The current study investigates the hot deformation behavior of Al-12Ce-0.4Sc alloy with an isothermal hot compression test at300-450°C/0.001-1s^(-1).Results show that the flow curves exhibit typical dynamic recovery(DRV)and slight flow-softening behavior.Additionally,the flow curves overlap owing to the dynamic strain aging(DSA)phenomenon at 400-450°C/0.01-0.1 s^(-1).Two different constitutive models were developed using the experimental data for hot deformation:(i)strain-compensated Arrhenius model(Method I)and(ii)logistic regression model(MethodⅡ).The average stress exponent(n)and apparent activation energy(Q)are 14.25 and 209.58 k J·mol^(-1),respectively.The hot-working processing map shows that the optimal processing condition is 400°C/1 s^(-1),and the maximum power dissipation efficiency is 22%.Stable and unstable domains indicated by the processing map were correlated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),and electron backscatter diffraction(EBSD)characterization techniques.The unstable domains are primarily associated with pro-eutectic Al11Ce3intermetallic fracture and interfacial cracks betweenα-Al and pro-eutectic Al_(11)Ce_(3).
基金Project(51301065)supported by the National Natural Science Foundation of ChinaProject(15B063)supported by the Youth Research Foundation of Education Bureau of Hunan Province,China
文摘Hot deformation behavior of extrusion preform of the spray-formed Al-9.0Mg-0.5Mn-0.1Ti alloy was studied using hot compression tests over deformation temperature range of 300-450 ℃ and strain rate range of 0.01-10 s-1. On the basis of experiments and dynamic material model, 2D processing maps and 3D power dissipation maps were developed for identification of exact instability regions and optimization of hot processing parameters. The experimental results indicated that the efficiency factor of energy dissipate （η） lowered to the minimum value when the deformation conditions located at the strain of 0.4, temperature of 300 ° C and strain rate of 1 s-1. The softening mechanism was dynamic recovery, the grain shape was mainly flat, and the portion of high angle grain boundary （〉15°） was 34%. While increasing the deformation temperature to 400 ° C and decreasing the strain rate to 0.1 s-1, a maximum value of η was obtained. It can be found that the main softening mechanism was dynamic recrystallization, the structures were completely recrystallized, and the portion of high angle grain boundary accounted for 86.5%. According to 2D processing maps and 3D power dissipation maps, the optimum processing conditions for the extrusion preform of the spray-formed Al？9.0Mg？0.5Mn？0.1Ti alloy were in the deformation temperature range of 340-450 ° C and the strain rate range of 0.01-0.1 s-1 with the power dissipation efficiency range of 38%？43%.
基金Project(51101052) supported by the National Natural Science Foundation of China
文摘The high-temperature deformation behavior of Cu-Ni-Si-P alloy was investigated by using the hot compression test in the temperature range of 600-800 ℃ and strain rate of 0.01-5 s-1. The hot deformation activation energy, Q, was calculated and the hot compression constitutive equation was established. The processing maps of the alloy were constructed based on the experiment data and the forging process parameters were then optimized based on the generated maps for forging process determination. The flow behavior and the microstructural mechanism of the alloy were studied. The flow stress of the Cu-Ni-Si-P alloy increases with increasing strain rate and decreasing deformation temperature, and the dynamic recrystallization temperature of alloy is around 700 ℃. The hot deformation activation energy for dynamic recrystallization is determined as 485.6 kJ/mol. The processing maps for the alloy obtained at strains of 0.3 and 0.5 were used to predict the instability regimes occurring at the strain rate more than 1 s-1 and low temperature （〈650 ℃）. The optimum range for the alloy hot deformation processing in the safe domain obtained from the processing map is 750-800 ℃ at the strain rate of 0.01-0.1 s i The characteristic microstructures predicted from the processing map agree well with the results of microstructural observations.
基金Project(2011CB605505)supported by the National Key Fundamental Research Development Project of ChinaProjects(51301204,51174233)supported by the National Natural Science Foundation of ChinaProject(2011JQ002)supported by the Fundamental Research Funds for the Central Universities of China
文摘High temperature compressive deformation behaviors of as-cast Ti-43Al-4Nb-1.4W-0.6B alloy was investigated at temperatures ranging from 1323 K to 1473 K, and strain rates from 0.001 s-1 to 1 s-1. The results indicated that the true stress-true strain curves show a dynamic flow softening behavior. The flow curves after the friction and the temperature compensations were employed to develop constitutive equations. The effects of temperature and the strain rate on the deformation behavior were represented by Zener-Holloman exponential equation. The influence of strain was incorporated in the constitutive analysis by considering the effect of the strain on material constants by a five-order polynomial. A revised model was proposed to describe the relationships among the flow stress, strain rate and temperature and the predicted flow stress curves were in good agreement with experimental results. Appropriate deformation processing parameters were suggested based on the processing map which was constructed from friction and temperature corrected flow curves, determined as 1343 K, 0.02 s-1 and were successfully applied in the canned forging of billets to simulate industrial work condition.
基金Project(51271203)supported by the National Natural Science Foundation of ChinaProject(CX2012B037)supported by the Hunan Provincial Innovation Foundation for Postgraduate,China+1 种基金Project(2013zzts017)supported by the Graduate Degree Thesis Innovation Foundation of Central South University,ChinaProject(2012bjjxj015)supported by the Excellent Doctor Degree Thesis Support Foundation of Central South University,China
文摘Hot compression test of a novel nickel-free white alloy Cu?12Mn?15Zn?1.5Al?0.3Ti?0.14B?0.1Ce (mass fraction, %) was conducted on a Gleeble?1500 machine in the temperature range of 600?800 °C and the strain rate range of 0.01?10 s?1. The constitutive equation and hot processing map of the alloy were built up according to its hot deformation behavior and hot working characteristics. The deformation activation energy of the alloy is 203.005 kJ/mol. An instability region appears in the hot deformation temperature of 600?700 °C and the strain rate range of 0.32?10 s?1 when the true strain of the alloy is up to 0.7. Under the optimal hot deformation condition of 800 °C and 10 s?1 the prepared specimen has good surface quality and interior structure. The designed nickel-free alloy has very similar white chromaticity with the traditional white copper alloy (Cu?15Ni?24Zn?1.5Pb), and the color difference between them is less than 1.5, which can hardly be distinguished by human eyes.
基金supported by the R&D Program of Korea Institute of Materials Sciencethe World Premier Materials Program funded by The Ministry of Knowledge Economy,Koreasupport from China Scholarship Council(CSC)
文摘The deformation behaviors of a new quaternary Mg-6Zn-1.5Cu-0.5Zr alloy at temperatures of 523-673 K and strain rates of 0.001-1 s-1 were studied by compressive tests using a Gleeble 3800 thermal-simulator.The results show that the flow stress increases as the deformation temperature decreases or as the strain rate increases.A strain-dependent constitutive equation and a feed-forward back-propagation artificial neural network were used to predict flow stress,which showed good agreement with experimental data.The processing map suggests that the domains of 643-673 K and 0.001-0.01 s-1 are corresponded to optimum conditions for hot working of the T4-treated Mg-6Zn-1.5Cu-0.5Zr alloy.
基金Project (51174233) supported by the National Natural Science Foundation of ChinaProject (2011CB605500) supported by National Basic Research program of China
文摘The flow stress features of PM Ti-47Al-2Cr-0.2Mo alloy were studied by isothermal compression in the temperature range from 1000 to 1150 °C with strain rates of 0.001-1 s-1 on Gleeble-1500 thermo-simulation machine.The results show that the deformation temperature and strain rate have obvious effects on the flow characteristic,and the flow stress increases with increasing strain rate and decreasing temperature.The processing maps under different deformation conditions were established.The processing maps of this alloy are sensitive to strains.The processing map at the strain of 0.5 exhibits two suitable deformation domains of 1000-1050 °C at 0.001-0.05 s-1 and 1050-1125 °C at 0.01-0.1 s-1.The optimum parameters for hot working of the alloy are deformation temperature of 1000 °C and strain rate of 0.001 s-1 according to the processing map and microstructure at true strain of 0.5.
基金Project(2010CB631203)supported by the National Basic Research Program of China
文摘Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79.
基金Project(2007CB613807)supported by the National Basic Research Program of ChinaProject(NCET-07-0696)supported by the New Century Excellent Talents in University,ChinaProject(35-TP-2009)supported by the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China
文摘Based on the experimental data of Ti40 alloy obtained from Gleeble-1500 thermal simulator,an artificial neural network model of high temperature flow stress as a function of strain,strain rate and temperature was established.In the network model,the input parameters of the model are strain,logarithm strain rate and temperature while flow stress is the output parameter.Multilayer perceptron（MLP） architecture with back-propagation algorithm is utilized.The present study achieves a good performance of the artificial neural network（ANN） model,and the predicted results are in agreement with experimental values.A processing map of Ti40 alloy is obtained with the flow stress predicted by the trained neural network model.The processing map developed by ANN model can efficiently track dynamic recrystallization and flow localization regions of Ti40 alloy during deforming.Subsequently,the safe and instable domains of hot working of Ti40 alloy are identified and validated through microstructural investigations.
基金Project(2011BAE22B01-1)supported by the National Key Technology R&D ProgramProject(2011DFA50903)supported by the International Science&Technology Cooperation Program of China
文摘The plastic flow behavior of a newly developed high ductility magnesium alloy, Mg-4Al-2Sn-Y-Nd, was investigated by hot compression from 200 to 400 ℃ with a strain rate of 1.5×10-3 to 7.5 s-1. The results reveal that the strain rate sensitivity factor （m） of the alloy is much lower than that of the AZ31 alloy, which implies that the alloy should be more suitable for processing at high strain rate. The constitutive relationship of the alloy deformed at elevated temperature was obtained by plotting the experimental data. The stress exponent of the alloy is 10.33, which reveals that climb-controlled dislocations creep is the dominated deformation mechanism. The processing-map technique was used to determine the practical processing window. The proper deformation temperature and strain rate of the cast alloy were determined as 350-400 ℃ and 0.01-0.03 s-1, respectively.
基金Project(2012AA030311)supported by the National High-tech Research and Development Program of ChinaProject(51421001)supported by the National Natural Science Foundation of ChinaProject(106112015CDJXY130002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300?550 °C and strain rate range of 0.001? 10 s?1 with Gleeble?3500 thermal simulator system. Processing maps of the CNTs/Al alloy at different strains were calculated to study the optimum processing domain. Microstructures before and after hot compressions were characterized by electron backscattered diffraction (EBSD) method. Stress?strain curves indicate that the flow stress increases with the increase of strain rate and the decrease of temperature. The processing maps of the CNTs/Al alloy at different strains show that the optimum processing domain is 500?550 °C, 10 s?1 for hot working. EBSD analysis demonstrates that fully dynamic recrystallization occurs in the optimum processing domain (high strainrate 10 s?1), whereas the main soften mechanism is dynamic recovery at low strain rate (0.001 s?1).
基金Project(2011ZX04014-051)supported by the Key Scientific and Technical Project of ChinaProjects(51375306,50905110)supported by the National Natural Science Foundation of China
文摘The three-dimensional （3D） processing maps considering strain based on the two-dimensional （2D） processing maps proposed by PRASAD can describe the distribution of the efficiency of power dissipation and flow instability regions at various temperatures, strain rates and strains, which exhibit intrinsic workability related to material itself. Finite element （FE） simulation can obtain the distribution of strain, strain rate, temperature and die filling status, which indicates state-of-stress （SOS） workability decided by die shape and different processing conditions. On the basis of this, a new material driven analysis method for hot deformation was put forward by the combination of FE simulation with 3D processing maps, which can demonstrate material workability of the entire hot deformation process including SOS workability and intrinsic workability. The hot forging process for hard-to-work metal magnesium alloy was studied, and the 3D thermomechanical FE simulation including 3D processing maps of complex hot forging spur bevel gear was first conducted. The hot forging experiments were carried out. The results show that the new method is reasonable and suitable to determine the aoorooriate nrocess narameters.
基金Project(2012AA030311)supported by the National High-tech Research and Development Program of ChinaProject(2010BB4074)supported by the Natural Science Foundation of Chongqing Municipality,ChinaProject(2010ZD-02)supported by the State Key Laboratory for Advanced Metals and Materials,China
文摘The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300-450 °C and strain rates of 0.001-1.0 s-1 with Gleeble-1500 D thermal simulator system. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The hyperbolic sine constitutive equation can describe the flow stress behavior of Al2O3/Al composites, and the deformation activation energy and constitutive equations were calculated. The processing maps of Al2O3/Al-2 μm and Al2O3/Al-1 μm composites at strain of 0.6 were obtained and the optimum processing domains are in ranges of 300-330 °C, 0.007-0.03 s-1 and 335-360 °C, 0.015-0.06 s-1 for hot working, respectively. The instability zones of flow behavior can also be recognized by the maps.
基金Project(51301143)supported by the National Natural Science Foundation of ChinaProject(2014M560727)supported by the National Postdoctoral Foundation of China+1 种基金Project(2015GZ0228)supported by the Sichuan Province Science-Technology Support Plan,ChinaProject(2682014CX001)supported by the Science and Technology Innovation Project of SWJTU University,China
文摘Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and strain rates of 0.0003?1.0 s?1. The constitutive equation was established, power dissipation (η) maps and hot processing maps were plotted. The microstructure evolution and dislocation distribution of domains with different values of η in power dissipation maps were also observed. The results show that the flow stress increases with decreasing temperature and increasing strain rate. The activation energy of the spray forming LSHR alloy is 1243.86 kJ/mol. When the value of η is 0.36 at the strain of 0.5, the domain in the processing map shows characteristics of typical dynamic recrystallization (DRX) and low dislocation density. According to the microstructure evolution and processing maps, the optimum processing condition for good hot workability of spray forming LSHR alloy can be summed up as:temperature range 1110?1150 °C; strain rate range 0.01?0.3 s?1.
基金Project(51274184)supported by the National Natural Science Foundation of ChinaProject(2013CB632205)supported by the National Basic Research Program of China
文摘The hot deformation behavior of as-cast Mg-8Zn-1Al-0.5Cu-0.5Mn alloy was studied by hot compression tests at temperatures of 200-350 °C and strain rates of 0.001-1 s-1.The results show that the flow stress increases significantly with increasing strain rate,and decreases as the temperature increases.The flow stress model based on the regression analysis was developed to predict the flow behavior of Mg-8Zn-1Al-0.5Cu-0.5Mn alloy during the hot compression,and the model shows a good agreement with experimental results.Meanwhile,the processing maps were established according to the dynamic materials model.The processing maps show that the increase of strain enlarges the instability domains,and the alloy shows good hot workability at high temperatures and low strain rates.
基金Project(51271076)supported by the National Natural Science Foundation of China
文摘Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.
基金Project(31115014)supported by the of Open Research Fund Program of State Key Laboratory of Advanced Design and Manufacture forVehicle Body(Hunan University)Project(12JJ9017)supported by the Natural Science Foundation of Hunan Province,China
文摘Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.
