Whipped cream is a delicious topping.You can make it at home or buy it in a can.People often put it on desserts such as cakes and pies.Whipped cream is great on ice cream and fruit,too.Do you like cream puffs?Some hav...Whipped cream is a delicious topping.You can make it at home or buy it in a can.People often put it on desserts such as cakes and pies.Whipped cream is great on ice cream and fruit,too.Do you like cream puffs?Some have whipped cream in them.Whipped cream is also good on hot chocolate and coffee.So,enjoy whipped cream on desserts and hot drinks today.It's National Whipped Cream Day!展开更多
Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening pa...Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.展开更多
The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal ho...The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal hot extrusion parameters are determined as ingot initial temperature of 380°C and extrusion speed of 3 mm/s.The hot-extruded aluminum alloy after T6 heat treatment presents superior mechanical properties with yield strength of 519.6 MPa,ultimate tensile strength of 582.1 MPa,and elongation of 11.0%.Compared with the properties of gravity-cast and liquid-forged alloys,the yield strength of hot-extruded alloy increases by 30.8%and 4.9%,and the ultimate tensile strength improves by 43.5%and 10.2%,respectively.The significant improvement in tensile strength of the hot-extruded alloys is attributed to the elimination of casting defects and the refinement of matrix grain and eutectic phases.In addition,the hot-extruded alloy demonstrates superior plasticity compared with the liquid-forged alloy.This is because severe plastic deformation occurs during hot extrusion,which effectively breaks and disperses the eutectic phases,facilitating the dissolution and precipitation of the second phases and inhibiting the microcrack initiation.展开更多
To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0....To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.展开更多
Theβsolidifiedγ-TiAl alloy holds important application value in the aerospace industry,while its com-plex phase compositions and geometric structures pose challenges to its microstructure control during the thermal-...Theβsolidifiedγ-TiAl alloy holds important application value in the aerospace industry,while its com-plex phase compositions and geometric structures pose challenges to its microstructure control during the thermal-mechanical process.The microstructure evolution of Ti-43Al-4Nb-1Mo-0.2B alloy at 1200℃/0.01 s−1 was investigated to clarify the coupling role of dynamic recrystallization(DRX)and phase transformation.The results revealed that the rate of DRX inα2+γlamellar colonies was comparatively slower than that inβo+γmixed structure,instead being accompanied by intense lamellar kinking and rotation.The initiation and development rates of DRX inα2,βo,andγphases decreased sequentially.The asynchronous DRX of the various geometric structures and phase compositions resulted in the un-even deformed microstructure,and the dynamic softening induced by lamellar kinking and rotation was replaced by strengthened DRX as strain increased.Additionally,the blockyα2 phase and the terminals ofα2 lamellae were the preferential DRX sites owing to the abundant activated slip systems.Theα2→βo transformation within lamellar colonies facilitated DRX and fragment ofα2 lamellae,while theα2→γtransformation promoted the decomposition ofα2 lamellae and DRX ofγlamellae.Moreover,the var-iedβo+γmixed structures underwent complicated evolution:(1)Theγ→βo transformation occurred at boundaries of lamellar colonies,followed by simultaneous DRX ofγlamellar terminals and neighboringβo phase;(2)DRX occurred earlier within the band-likeβo phase,with the delayed DRX in enclosedγphase;(3)DRX within theβo synapses and neighboringγphase was accelerated owing to generation of elastic stress field;(4)Dispersedβo particles triggered particle stimulated nucleation(PSN)ofγphase.Eventually,atomic diffusion along crystal defects inβo andγphases caused fracture of band-likeβo phase and formation of massiveβo particles,impeding grain boundary migration and hindering DRXed grain growth ofγphase.展开更多
Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prep...Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.展开更多
China has abundant resources of hot dry rocks.However,due to the fact that the evaluation methods for favorable areas are mainly qualitative,and the evaluation indicators and standards are inconsistent,which restrict ...China has abundant resources of hot dry rocks.However,due to the fact that the evaluation methods for favorable areas are mainly qualitative,and the evaluation indicators and standards are inconsistent,which restrict the evaluation efficiency and exploration process of dry hot rocks.This paper is based on the understanding of the geologic features and genesis mechanisms of hot dry rocks in China and abroad.By integrating the main controlling factors of hot dry rock formation,and using index grading and quantification,the fuzzy hierarchical comprehensive method is applied to establish an evaluation system and standards for favorable areas of hot dry rocks.The evaluation system is based on four indicators:heat source,thermal channel,thermal reservoir and cap rock.It includes 11 evaluation parameters,including time of magmatic/volcanic activity,depth of molten mass or magma chamber,distribution of discordogenic faults,burial depth of thermal reservoir,cap rock type and thickness,surface thermal anomaly,heat flow,geothermal gradient,Moho depth,Curie depth,Earthquake magnitude and focal depth.Each parameter is divided into 3 levels.Applying this evaluation system to assess hot dry rock in central Inner Mongolia revealed that Class I favorable zones cover approximately 494 km^(2),while Class II favorable zones span about 5.7×10^(4) km^(2).The Jirgalangtu Sag and Honghaershute Sag in the Erlian Basin,along with Reshuitang Town in Keshiketeng Banner,Reshui Town in Ningcheng County,and Reshuitang Town in Aohan Banner of Chifeng City,are identified as Class I favorable zones for hot dry rock resources.These areas are characterized by high-temperature subsurface molten bodies or magma chambers serving as high-quality heat sources,shallow thermal reservoir depths,and overlying thick sedimentary rock layers acting as caprock.The establishment and application of the evaluation system for favorable areas of hot dry rock are expected to provide new approaches and scientific basis for guiding the practice of selecting hot dry rock areas in China.展开更多
An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of t...An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.展开更多
Hot deformation with high strain rate has been paid more attention due to its high efficiency and low cost,however,the strain rate dependent dynamic recrystallization(DRX)and texture evolution in hot deformation proce...Hot deformation with high strain rate has been paid more attention due to its high efficiency and low cost,however,the strain rate dependent dynamic recrystallization(DRX)and texture evolution in hot deformation process,which affect the formability of metals,are lack of study.In this work,the DRX behavior and texture evolution of Mg-8Gd-1Er-0.5Zr alloy hot compressed with strain rates of 0.1 s^(−1),1 s^(−1),10 s^(−1) and 50 s^(−1) are studied,and the corresponding dominant mechanisms for DRX and texture weakening are discussed.Results indicated the DRX fraction was 20%and the whole texture intensity was 16.89 MRD when the strain rate was 0.1 s^(−1),but they were 76%and 6.55 MRD,respectively,when the strain rate increased to 50 s^(−1).The increment of DRX fraction is suggested to result from the reduced DRX critical strain and the increased dislocation density as well as velocity,while the weakened whole texture is attributed to the increased DRX grains.At the low strain rate of 0.1 s^(−1),discontinuous DRX(DDRX)was the dominant,but the whole texture was controlled by the deformed grains with the preferred orientation of{0001}⊥CD,because the number of DDRX grains was limited.At the high strain rate of 50 s^(−1),continuous DRX(CDRX)and twin-induced DRX(TDRX)were promoted,and more DRX grains resulted in orientation randomization.The whole texture was mainly weakened by CDRX and TDRX grains,in which CDRX plays a major role.The results of present work are significant for understanding the hot workability of Mg-RE alloys with a high strain rate.展开更多
The hot deformation behavior of Pt−10Ir alloy was studied under a wide range of deformation parameters.At a low deformation temperature(950−1150℃),the softening mechanism is primarily dynamic recovery.In addition,dyn...The hot deformation behavior of Pt−10Ir alloy was studied under a wide range of deformation parameters.At a low deformation temperature(950−1150℃),the softening mechanism is primarily dynamic recovery.In addition,dynamic recrystallization by progressive lattice rotation near grain boundaries(DRX by LRGBs)and microshear bands assisted dynamic recrystallization(MSBs assisted DRX)coordinate the deformation.However,it is difficult for the dynamic softening to offset the stain hardening due to a limited amount of DRXed grains.At a high deformation temperature(1250−1350℃),three main DRX mechanisms associated with strain rates occur:DRX by LRGBs,DRX by a homogeneous increase in misorientation(HIM)and geometric DRX(GDRX).With increasing strain,DRX by LRGBs is enhanced gradually under high strain rates;the“pinch-off”effect is enhanced at low strain rates,which was conducive to the formation of a uniform and fine microstructure.展开更多
Due to the existence of oxide layer on the surface of Q235 steel,it is difficult to directly achieve metallurgical bonding with tin-lead al-loy,in order to solve this problem,this paper designed and successfully prepa...Due to the existence of oxide layer on the surface of Q235 steel,it is difficult to directly achieve metallurgical bonding with tin-lead al-loy,in order to solve this problem,this paper designed and successfully prepared steel surface activation liquid with the composition of 1 L distilled water,130 g ZnCl_(2),90 g NH_(4)Cl,5 mL 6501,and adding C_(3)H_(6)O_(3)to adjust pH 3.The results show that the activated mol-ten tin-lead alloy has a low wetting angle of 7.5°on the steel surface,which was then successfully plated on the steel surface by hot-dipping.The microstructural analysis of the plating-substrate interface and the thermodynamic calculation of the reaction can be found.The main structure of the interfacial reaction layer isα-Fe/FeSn_(2)/α-Pb+β-Sn.展开更多
An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on t...An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.展开更多
The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practi...The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.展开更多
In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain r...In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).展开更多
The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulati...The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulating the measured flow curves,we successfully constructed deformation activation energy(Q)maps and processing maps for identifying the region of flow instability.We concluded the following consequences of Nb-V alloying for MMS.(i)The critical strain increases and the increment diminishes with the increasing deformation temperature,suggesting that NbC precipitates more efficiently retard dynamic recrystallization(DRX)in MMS compared with solute Nb.(ii)The deformation activation energy of MMS is significantly increased and even higher than that of some reported high Mn steels,suggesting that its ability to retard DRX is greater than that of the high Mn content.(iii)The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress,in which fine recrystallized and coarse unrecrystallized grains are present.展开更多
In engineering practice,it is often necessary to determine functional relationships between dependent and independent variables.These relationships can be highly nonlinear,and classical regression approaches cannot al...In engineering practice,it is often necessary to determine functional relationships between dependent and independent variables.These relationships can be highly nonlinear,and classical regression approaches cannot always provide sufficiently reliable solutions.Nevertheless,Machine Learning(ML)techniques,which offer advanced regression tools to address complicated engineering issues,have been developed and widely explored.This study investigates the selected ML techniques to evaluate their suitability for application in the hot deformation behavior of metallic materials.The ML-based regression methods of Artificial Neural Networks(ANNs),Support Vector Machine(SVM),Decision Tree Regression(DTR),and Gaussian Process Regression(GPR)are applied to mathematically describe hot flow stress curve datasets acquired experimentally for a medium-carbon steel.Although the GPR method has not been used for such a regression task before,the results showed that its performance is the most favorable and practically unrivaled;neither the ANN method nor the other studied ML techniques provide such precise results of the solved regression analysis.展开更多
文摘Whipped cream is a delicious topping.You can make it at home or buy it in a can.People often put it on desserts such as cakes and pies.Whipped cream is great on ice cream and fruit,too.Do you like cream puffs?Some have whipped cream in them.Whipped cream is also good on hot chocolate and coffee.So,enjoy whipped cream on desserts and hot drinks today.It's National Whipped Cream Day!
基金financial support of the National Natural Science Foundation of China(No.52371103)the Fundamental Research Funds for the Central Universities,China(No.2242023K40028)+1 种基金the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.AMM2023B01).financial support of the Research Fund of Shihezi Key Laboratory of AluminumBased Advanced Materials,China(No.2023PT02)financial support of Guangdong Province Science and Technology Major Project,China(No.2021B0301030005)。
文摘Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.
基金Natural Science Foundation of Shandong Province of China(ZR2023QE193)。
文摘The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal hot extrusion parameters are determined as ingot initial temperature of 380°C and extrusion speed of 3 mm/s.The hot-extruded aluminum alloy after T6 heat treatment presents superior mechanical properties with yield strength of 519.6 MPa,ultimate tensile strength of 582.1 MPa,and elongation of 11.0%.Compared with the properties of gravity-cast and liquid-forged alloys,the yield strength of hot-extruded alloy increases by 30.8%and 4.9%,and the ultimate tensile strength improves by 43.5%and 10.2%,respectively.The significant improvement in tensile strength of the hot-extruded alloys is attributed to the elimination of casting defects and the refinement of matrix grain and eutectic phases.In addition,the hot-extruded alloy demonstrates superior plasticity compared with the liquid-forged alloy.This is because severe plastic deformation occurs during hot extrusion,which effectively breaks and disperses the eutectic phases,facilitating the dissolution and precipitation of the second phases and inhibiting the microcrack initiation.
基金National Natural Science Foundation of China(52105385)Stable Support Plan Program of Shenzhen Natural Science Fund(20220810132537001)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2022A1515010781)Joint Fund of Henan Province Science and Technology R&D Program(225200810002)Fundamental Research Funds of Henan Academy of Sciences(240621041)。
文摘To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.
基金financially supported by the National Key Re-search and Development Program of China(No.2021YFB3702604)the National Natural Science Foundation of China(No.52174377)+1 种基金the Chongqing Natural Science Foundation Project(No.CSTB2023NSCQ-MSX0824)This work was also supported by the Shaanxi Materials Analysis&Research Center and the Analytical&Testing Center of NPU.
文摘Theβsolidifiedγ-TiAl alloy holds important application value in the aerospace industry,while its com-plex phase compositions and geometric structures pose challenges to its microstructure control during the thermal-mechanical process.The microstructure evolution of Ti-43Al-4Nb-1Mo-0.2B alloy at 1200℃/0.01 s−1 was investigated to clarify the coupling role of dynamic recrystallization(DRX)and phase transformation.The results revealed that the rate of DRX inα2+γlamellar colonies was comparatively slower than that inβo+γmixed structure,instead being accompanied by intense lamellar kinking and rotation.The initiation and development rates of DRX inα2,βo,andγphases decreased sequentially.The asynchronous DRX of the various geometric structures and phase compositions resulted in the un-even deformed microstructure,and the dynamic softening induced by lamellar kinking and rotation was replaced by strengthened DRX as strain increased.Additionally,the blockyα2 phase and the terminals ofα2 lamellae were the preferential DRX sites owing to the abundant activated slip systems.Theα2→βo transformation within lamellar colonies facilitated DRX and fragment ofα2 lamellae,while theα2→γtransformation promoted the decomposition ofα2 lamellae and DRX ofγlamellae.Moreover,the var-iedβo+γmixed structures underwent complicated evolution:(1)Theγ→βo transformation occurred at boundaries of lamellar colonies,followed by simultaneous DRX ofγlamellar terminals and neighboringβo phase;(2)DRX occurred earlier within the band-likeβo phase,with the delayed DRX in enclosedγphase;(3)DRX within theβo synapses and neighboringγphase was accelerated owing to generation of elastic stress field;(4)Dispersedβo particles triggered particle stimulated nucleation(PSN)ofγphase.Eventually,atomic diffusion along crystal defects inβo andγphases caused fracture of band-likeβo phase and formation of massiveβo particles,impeding grain boundary migration and hindering DRXed grain growth ofγphase.
基金support from CAS Project for Young Scientists in Basic Research(YSBR-025)and the Technology Innovation(RCJJ-145-24-39)R.P.Guo acknowledges the financial support from the National Natural Science Foundation of China(No.52401104)+1 种基金the Fundamental Research Program of Shanxi Province(No.202203021221072)the China Postdoctoral Science Foundation(No.2024M753298).
文摘Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.
基金Supported by PetroChina Prospective and Basic Technological Project(2022DJ5503).
文摘China has abundant resources of hot dry rocks.However,due to the fact that the evaluation methods for favorable areas are mainly qualitative,and the evaluation indicators and standards are inconsistent,which restrict the evaluation efficiency and exploration process of dry hot rocks.This paper is based on the understanding of the geologic features and genesis mechanisms of hot dry rocks in China and abroad.By integrating the main controlling factors of hot dry rock formation,and using index grading and quantification,the fuzzy hierarchical comprehensive method is applied to establish an evaluation system and standards for favorable areas of hot dry rocks.The evaluation system is based on four indicators:heat source,thermal channel,thermal reservoir and cap rock.It includes 11 evaluation parameters,including time of magmatic/volcanic activity,depth of molten mass or magma chamber,distribution of discordogenic faults,burial depth of thermal reservoir,cap rock type and thickness,surface thermal anomaly,heat flow,geothermal gradient,Moho depth,Curie depth,Earthquake magnitude and focal depth.Each parameter is divided into 3 levels.Applying this evaluation system to assess hot dry rock in central Inner Mongolia revealed that Class I favorable zones cover approximately 494 km^(2),while Class II favorable zones span about 5.7×10^(4) km^(2).The Jirgalangtu Sag and Honghaershute Sag in the Erlian Basin,along with Reshuitang Town in Keshiketeng Banner,Reshui Town in Ningcheng County,and Reshuitang Town in Aohan Banner of Chifeng City,are identified as Class I favorable zones for hot dry rock resources.These areas are characterized by high-temperature subsurface molten bodies or magma chambers serving as high-quality heat sources,shallow thermal reservoir depths,and overlying thick sedimentary rock layers acting as caprock.The establishment and application of the evaluation system for favorable areas of hot dry rock are expected to provide new approaches and scientific basis for guiding the practice of selecting hot dry rock areas in China.
基金supported by the National Natural Science Foundation of China(No.51905123)Major Scientific and Technological Innovation Program of Shandong Province,China(Nos.2020CXGC010303,2022ZLGX04)Key R&D Programme of Shandong Province,China(No.2022JMRH0308).
文摘An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.
基金supported by the Nation Key Research and Development Program of China(No.2021YFB3701100).
文摘Hot deformation with high strain rate has been paid more attention due to its high efficiency and low cost,however,the strain rate dependent dynamic recrystallization(DRX)and texture evolution in hot deformation process,which affect the formability of metals,are lack of study.In this work,the DRX behavior and texture evolution of Mg-8Gd-1Er-0.5Zr alloy hot compressed with strain rates of 0.1 s^(−1),1 s^(−1),10 s^(−1) and 50 s^(−1) are studied,and the corresponding dominant mechanisms for DRX and texture weakening are discussed.Results indicated the DRX fraction was 20%and the whole texture intensity was 16.89 MRD when the strain rate was 0.1 s^(−1),but they were 76%and 6.55 MRD,respectively,when the strain rate increased to 50 s^(−1).The increment of DRX fraction is suggested to result from the reduced DRX critical strain and the increased dislocation density as well as velocity,while the weakened whole texture is attributed to the increased DRX grains.At the low strain rate of 0.1 s^(−1),discontinuous DRX(DDRX)was the dominant,but the whole texture was controlled by the deformed grains with the preferred orientation of{0001}⊥CD,because the number of DDRX grains was limited.At the high strain rate of 50 s^(−1),continuous DRX(CDRX)and twin-induced DRX(TDRX)were promoted,and more DRX grains resulted in orientation randomization.The whole texture was mainly weakened by CDRX and TDRX grains,in which CDRX plays a major role.The results of present work are significant for understanding the hot workability of Mg-RE alloys with a high strain rate.
基金financial supports from the National Natural Science Foundation of China(Nos.52161023,51901204)Science and Technology Project of Yunnan Precious Metal Laboratory,China(No.YPML-2023050208)+1 种基金Yunnan Science and Technology Planning Project,China(Nos.202201AU070010,202301AT070276,202302AB080008,202303AA080001)Postgraduate Research and Innovation Foundation of Yunnan University,China(No.2021Y338).
文摘The hot deformation behavior of Pt−10Ir alloy was studied under a wide range of deformation parameters.At a low deformation temperature(950−1150℃),the softening mechanism is primarily dynamic recovery.In addition,dynamic recrystallization by progressive lattice rotation near grain boundaries(DRX by LRGBs)and microshear bands assisted dynamic recrystallization(MSBs assisted DRX)coordinate the deformation.However,it is difficult for the dynamic softening to offset the stain hardening due to a limited amount of DRXed grains.At a high deformation temperature(1250−1350℃),three main DRX mechanisms associated with strain rates occur:DRX by LRGBs,DRX by a homogeneous increase in misorientation(HIM)and geometric DRX(GDRX).With increasing strain,DRX by LRGBs is enhanced gradually under high strain rates;the“pinch-off”effect is enhanced at low strain rates,which was conducive to the formation of a uniform and fine microstructure.
基金supported by National Natural Science Foundation of China(Grant No.52305353)Postdoctoral Science Foundation of China(Grant No.2023M7408938).
文摘Due to the existence of oxide layer on the surface of Q235 steel,it is difficult to directly achieve metallurgical bonding with tin-lead al-loy,in order to solve this problem,this paper designed and successfully prepared steel surface activation liquid with the composition of 1 L distilled water,130 g ZnCl_(2),90 g NH_(4)Cl,5 mL 6501,and adding C_(3)H_(6)O_(3)to adjust pH 3.The results show that the activated mol-ten tin-lead alloy has a low wetting angle of 7.5°on the steel surface,which was then successfully plated on the steel surface by hot-dipping.The microstructural analysis of the plating-substrate interface and the thermodynamic calculation of the reaction can be found.The main structure of the interfacial reaction layer isα-Fe/FeSn_(2)/α-Pb+β-Sn.
基金supported by the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20233326)the Chongqing Science Fund for Distinguished Young Scholars(Grant No.CSTB2022NSCQJQX0028)the National Natural Science Foundation of China(Grant Nos.U23A20597,52274112).
文摘An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.
基金support of this work by the National Natural Science Foundation of China (Grant Nos.41972316 and 41672252).
文摘The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.
基金fnancially supported by the Scientifc Research Project of the Department of Education in Hunan Prov ince,China(Grant No.23B0533).
文摘In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).
基金financial support from the National Natural Science Foundation of China(Nos.52233018 and 51831002)the China Baowu Low Carbon Metallurgy Innovation Foudation(No.BWLCF202213)。
文摘The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulating the measured flow curves,we successfully constructed deformation activation energy(Q)maps and processing maps for identifying the region of flow instability.We concluded the following consequences of Nb-V alloying for MMS.(i)The critical strain increases and the increment diminishes with the increasing deformation temperature,suggesting that NbC precipitates more efficiently retard dynamic recrystallization(DRX)in MMS compared with solute Nb.(ii)The deformation activation energy of MMS is significantly increased and even higher than that of some reported high Mn steels,suggesting that its ability to retard DRX is greater than that of the high Mn content.(iii)The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress,in which fine recrystallized and coarse unrecrystallized grains are present.
基金supported by the SP2024/089 Project by the Faculty of Materials Science and Technology,VˇSB-Technical University of Ostrava.
文摘In engineering practice,it is often necessary to determine functional relationships between dependent and independent variables.These relationships can be highly nonlinear,and classical regression approaches cannot always provide sufficiently reliable solutions.Nevertheless,Machine Learning(ML)techniques,which offer advanced regression tools to address complicated engineering issues,have been developed and widely explored.This study investigates the selected ML techniques to evaluate their suitability for application in the hot deformation behavior of metallic materials.The ML-based regression methods of Artificial Neural Networks(ANNs),Support Vector Machine(SVM),Decision Tree Regression(DTR),and Gaussian Process Regression(GPR)are applied to mathematically describe hot flow stress curve datasets acquired experimentally for a medium-carbon steel.Although the GPR method has not been used for such a regression task before,the results showed that its performance is the most favorable and practically unrivaled;neither the ANN method nor the other studied ML techniques provide such precise results of the solved regression analysis.
