The soft-hard combined structures involving varying microhardness on the specimen surface of grey cast iron,processed by bionic laser technology,exhibit excellent wear resistance under dry sliding condition.Both the p...The soft-hard combined structures involving varying microhardness on the specimen surface of grey cast iron,processed by bionic laser technology,exhibit excellent wear resistance under dry sliding condition.Both the primary phase(PP)and the laser-treated phase(LP)play pivotal roles in the wear performance of grey cast iron,in association with various combinations of PP and LP microhardness,originating from different laser processing and heat treatment.Owing to the optimized combination of microhardness,the result exhibits the dominant role of LP,with higher microhardness,in wear test,indicating that this technology,apart from producing complex structures,can also act as a design-process method to modify the tribological properties of grey cast iron,and thus providing a feasible approach to tailor the surface microhardness and to modify the wear performance of grey cast iron.Moreover,a threshold of wear resistance is obtained,while LP microhardness is above 900 HV;meanwhile,beyond it,the change of PP microhardness has only minor impact on wear performance.Finite element analysis shows that,in line with varying microhardness combination,distinct stress distribution on specimen surface is achieved,agreeing well with the good wear resistance and tailorable microhardness of LP and PP.展开更多
The external hard TiN ceramic layer and an internal reinforced NiTi matrix were controlled by combining nitriding and solution treatment to achieve ultra-high micro-hardness and excellent wear performance.In addition,...The external hard TiN ceramic layer and an internal reinforced NiTi matrix were controlled by combining nitriding and solution treatment to achieve ultra-high micro-hardness and excellent wear performance.In addition,the effects of nitriding and solution treatment on the microstructure evolution,martensitic transformation,and mechanical and functional properties of 60NiTi alloys were investigated.Compared with 60NiTi alloy,a harder TiN layer appeared at the surface of 60NiTi alloy with nitriding treatment.Meanwhile,a Ni_(3)Ti layer formed under the bottom of TiN layer owing to the consumption of Ti in matrix induced by formation of TiN layer.Upon undergoing solution treatment,the precipitates evolved from the coexistence of Ni_(3)Ti and Ni_(3)Ti_(2)phase to Ni_(4)Ti_(3)phase.The introduction of the outer harder TiN ceramic layer had a constraint of martensitic transformation of 60NiTi alloy,which led to the reduction of martensitic transformation temperature(Ms)and the suppression of martensitic transformation.Importantly,the construction of outermost harder TiN ceramic layer at the surface of B2-NiTi matrix enhanced Ni_(4)Ti_(3)phase improved significantly the microhardness and wear performances by the nitriding and followed solution treatment.Meanwhile,the high compressive fracture strength,fracture strain and superior superelasticity of 60NiTi alloy can be maintained.展开更多
In this study,AZ31 Mg alloy sheets were processed by a severe plastic deformation(SPD)technique called forging-bending repeated deformation(FBRD).The effect on the microstructure and microhardness of AZ31 Mg alloy thr...In this study,AZ31 Mg alloy sheets were processed by a severe plastic deformation(SPD)technique called forging-bending repeated deformation(FBRD).The effect on the microstructure and microhardness of AZ31 Mg alloy through FBRD was investigated with increasing temperature treatment and a 90°cross route.The results reveal that the effective strain increases with the number of passes.The flow uniformity is effectively enhanced due to alterations in shear deformation direction.After four passes of deformation,the average grain size is refined by 79.3%compared to the initial specimen.The grain refinement mechanism predominantly originates from the synergistic effects of discontinuous dynamic recrystallization(DDRX),continuous dynamic recrystallization(CDRX),and twinning-induced recrystallization(TDRX).The formation of{1012}extension twins(ET)significantly contributes to coarse grain subdivision and plastic deformation coordinated.Furthermore,pyramidal<c+a>slip activation effectively enhances the plasticity of Mg alloys.By post four-pass processing,the alloy exhibits a microhardness of 81.9HV,primarily governed by fine grain strengthening and dislocation strengthening mechanisms.展开更多
激光定向能量沉积(laser directed energy deposition,LDED)凭借高效率与工艺柔性,正成为解决室温高脆性和高活性的TiAl4822(Ti-48Al-2Cr-2Nb)合金传统工艺难加工、难制备大型复杂构件问题的关键途径,以充分发挥其航空发动机等高温轻质...激光定向能量沉积(laser directed energy deposition,LDED)凭借高效率与工艺柔性,正成为解决室温高脆性和高活性的TiAl4822(Ti-48Al-2Cr-2Nb)合金传统工艺难加工、难制备大型复杂构件问题的关键途径,以充分发挥其航空发动机等高温轻质部件的理想材料潜力。然而,LDED过程中快速熔融-凝固循环会产生极大的温度梯度和残余应力,从而导致构件开裂,但目前尚无成熟手段能够完全抑制裂纹产生。本工作利用整体高温辅助LDED制备出30 mm×25 mm×6 mm致密无裂纹的TiAl4822合金薄壁构件,并对其宏观形貌、微观组织、孔隙率及显微硬度进行研究。研究结果表明:在常温条件下,LDED制备的TiAl4822合金薄壁样件易发生以解理为主的脆性断裂,显微组织以细小等轴晶为主;引入800℃整体高温辅助后,沉积层晶粒定向生长为自下而上倾斜的柱状晶,孔隙率从0.05%降至0.008%,孔径分布更均匀,表面未见宏观裂纹;与此同时,显微硬度由常温样件的390.46HV_(0.2)降至354.94HV_(0.2),这主要归因于在高温辅助条件下晶粒长大、晶界减少及析出相中γ相的含量相对增加。因此,整体高温辅助不仅有效抑制裂纹与大尺寸孔隙的产生,还优化微观组织均匀性,为TiAl4822合金的高致密、高性能制备提供新途径。展开更多
A detailed investigation for the influence of post weld heat treatment （PWHT） on the microstructure of TC4 and TC17 dissimilar joints was analyzed. The fully transformed microstructure in the as-welded zone indicate...A detailed investigation for the influence of post weld heat treatment （PWHT） on the microstructure of TC4 and TC17 dissimilar joints was analyzed. The fully transformed microstructure in the as-welded zone indicated that the peak temperature exceeded theβ-transus temperature at the weld interface during linear friction welding. TC4 side was mainly composed of martensiteα′phase with random distribution and it was singleβfor that of TC17. In the thermomechanically affected zones of TC4 and TC17, the structure undergoes severe plastic deformation and re-orientation, yet without altering the phase fractions. After PWHT, in the weld zone of TC4 alloy, the phase transformationα′→α＋βoccurred and the acicularαwas coarsened, which resulted in a decrease in hardness. In the weld zone of TC17 alloy, fineαphase precipitated at the grain boundary and withinβgrains, which resulted in a sharp increase in hardness.展开更多
Directionally solidified （DS） specimens of Nb-Ti-Si based ultrahigh temperature alloy were heat-treated at （1 500 ℃, 50 h） and （1 500 ℃, 50 h） ＋ （1 100 ℃, 50 h）, respectively. The results show that the mic...Directionally solidified （DS） specimens of Nb-Ti-Si based ultrahigh temperature alloy were heat-treated at （1 500 ℃, 50 h） and （1 500 ℃, 50 h） ＋ （1 100 ℃, 50 h）, respectively. The results show that the microstructures become uniform, the long and big primary （Nb,X）sSi3 （X represents Ti and Hf elements） plates in the DS specimens are broken into small ones, and the eutectic cells lose their lamellar morphology and their interfaces become blurry after heat-treatment. Meanwhile, the （Nb,X）sSi3 slices in the eutectic cells of the DS specimens coarsen obviously after heat-treatment. Homogenizing and aging treatments could effectively eliminate elemental microsegregation, and the segregation ratios of all elements in niobium solid solution （Nbss） in different regions tend to 1. After heat-treatment, the microhardness of retained eutectic cells increases evidently, and the maximum value reaches HV1 404.57 for the specimen directionally solidified with a withdrawing rate of 100 μm/s and then heat-treated at （1 500 ℃, 50 h） ＋ （1 100 ℃, 50 h）, which is 72.8 % higher than that under DS condition.展开更多
The squeeze pressure field and power ultrasonic field were applied during the conventional casting process of Al-5.0Cu alloy simultaneously. The effects of individual squeeze pressure or power ultrasonic and their cou...The squeeze pressure field and power ultrasonic field were applied during the conventional casting process of Al-5.0Cu alloy simultaneously. The effects of individual squeeze pressure or power ultrasonic and their coupling on the microstructures and microhardness of Al-5.0Cu alloy were studied by optical microscopy, scanning electron microscopy, image analysis and micro Vickers hardness test. The results show that compared with the conventional casting, refined microstructures, homogeneous distribution of α（Al） and θ（Al2Cu） and improved microhardness can be obtained when squeeze pressure or power ultrasonic is applied individually. For the case of combined fields, both the treated region and the improvement of microstructure and properties can be enhanced.展开更多
The thermal expansion behavior, microhardness and electrochemical corrosion resistance of Au52Cu27Ag17-x（NiZn0.5）x （x=0,6 and 12） alloys were investigated by dilatometer （DIL）, microhardness tester, electrochemi...The thermal expansion behavior, microhardness and electrochemical corrosion resistance of Au52Cu27Ag17-x（NiZn0.5）x （x=0,6 and 12） alloys were investigated by dilatometer （DIL）, microhardness tester, electrochemical workstation, X-ray diffractometer（XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and X-ray photoelectron spectroscopy （XPS）.With increasing x, the relative length expansion and DIL maximum temperature Tl m （i.e., thermal stability） of the alloys increase inthermal expansion measurements, which can be explained by the change of the atomic binding energy, mismatch entropy togetherwith phase transformation. With the increase of x, the microhardness can be improved, but the corrosion resistance decreases; inaddition, the anodic peak current densities of polarization curves decrease, which are related closely with the solid solution degreeand dissolution of Ag, Ni and Zn alloying elements in Cl^- -containing solution.展开更多
The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in Ti6 Al4 V laser-wel...The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in Ti6 Al4 V laser-welded joints with different welding speeds. The microhardness measured on the fusion line(H_m) is the highest from the weld center to the base metal. H_m increases with increasing weld width in a welded joint and increasing degree of the non-uniformity in all studied welded joints. The microhardness decreases from the weld metal to the base metal with decreasing amount of martensite α’ and increasing amount of original α phase. When the microstructure is mainly composed of martensite α’, the microhardness changes with the cooling rate, grain size of the martensite, and peak values of the fraction of misorientation angle of the martensite in a wide weld metal zone or weld center at different welding speeds, whereas the difference is small in a narrow weld metal zone.展开更多
To design microstructure and microhardness in the additive manufacturing(AM)of nickel(Ni)-based superalloys,the present work develops a novel data-driven approach that combines physics-based models,experimental measur...To design microstructure and microhardness in the additive manufacturing(AM)of nickel(Ni)-based superalloys,the present work develops a novel data-driven approach that combines physics-based models,experimental measurements,and a data-mining method.The simulation is based on a computational thermal-fluid dynamics(CtFD)model,which can obtain thermal behavior,solidification parameters such as cooling rate,and the dilution of solidified clad.Based on the computed thermal information,dendrite arm spacing and microhardness are estimated using well-tested mechanistic models.Experimental microstructure and microhardness are determined and compared with the simulated values for validation.To visualize process-structure-properties(PSPs)linkages,the simulation and experimental datasets are input to a data-mining model-a self-organizing map(SOM).The design windows of the process parameters under multiple objectives can be obtained from the visualized maps.The proposed approaches can be utilized in AM and other data-intensive processes.Data-driven linkages between process,structure,and properties have the potential to benefit online process monitoring control in order to derive an ideal microstructure and mechanical properties.展开更多
The Ti-20Zr-6.5Al-4V(T20Z,wt%)alloy surface was treated by the process of laser surface nitriding.The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120...The Ti-20Zr-6.5Al-4V(T20Z,wt%)alloy surface was treated by the process of laser surface nitriding.The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120 to 240 W.All laser-treated T20Z samples show two regions with distinctly different microstructural features,as compared with the untreated substrate:dense TiN dendrites and(α+β)-Ti(remelting zone,RMZ),nanoscaleαlaths doped with part of p phase(heat-affected zone,HAZ).The formation of TiN dendrites can be analyzed by a series of complex reactions during the process of melting and solidification.The increase in laser power results in the increase in content of TiN dendrite which is mainly due to the increase in energy input.In HAZ,the self-quenching effect leads to the formation of nanoscale a laths and the residue ofβphase.Microhardness profile of different regions was measured from the surface to the interior,and the highest microhardness was obtained(~HV 916.8)in the RMZ,as the laser power was set to 240 W.In the present study,we explained various microstructural characteristics induced by laser surface nitriding treatment.展开更多
Severe plastic deformation of Ti-10V-2Fe-3Al alloy in the surface region was caused by shot peening at air pressure of 0.6 MPa with processing time ranging from 1 to 45 min.The results showed that the thickness of sur...Severe plastic deformation of Ti-10V-2Fe-3Al alloy in the surface region was caused by shot peening at air pressure of 0.6 MPa with processing time ranging from 1 to 45 min.The results showed that the thickness of surface deformation layer was proportio nal to the processing time,the microhardness of the shot-peened surface in creased from 280 to 385 HV,and the depth of highly hardening layers arrived at 200μm.It was worth noting that a grain size gradient from nanocrystalline on the surface toward coarse grain in the matrix was obtained during the shot peening process and the minimum grain size in the top surface after shot peening was about 100-200 nm.展开更多
In this work,the nickel-based powder metallurgy superalloy FGH95 was selected as experimental material,and the experimental parameters in multiple overlap laser shock processing(LSP)treatment were selected based on or...In this work,the nickel-based powder metallurgy superalloy FGH95 was selected as experimental material,and the experimental parameters in multiple overlap laser shock processing(LSP)treatment were selected based on orthogonal experimental design.The experimental data of residual stress and microhardness were measured in the same depth.The residual stress and microhardness laws were investigated and analyzed.Artificial neural network(ANN)with four layers(4-N-(N-1)-2)was applied to predict the residual stress and microhardness of FGH95 subjected to multiple overlap LSP.The experimental data were divided as training-testing sets in pairs.Laser energy,overlap rate,shocked times and depth were set as inputs,while residual stress and microhardness were set as outputs.The prediction performances with different network configuration of developed ANN models were compared and analyzed.The developed ANN model with network configuration of 4-7-6-2 showed the best predict performance.The predicted values showed a good agreement with the experimental values.In addition,the correlation coefficients among all the parameters and the effect of LSP parameters on materials response were studied.It can be concluded that ANN is a useful method to predict residual stress and microhardness of material subjected to LSP when with limited experimental data.展开更多
基金supported by Project 985-High Performance Materials of Jilin University and the Project 985-Biomimetic Engineering Science and Technology Innovation and National Natural Science Foundation of China(No.51275200).
文摘The soft-hard combined structures involving varying microhardness on the specimen surface of grey cast iron,processed by bionic laser technology,exhibit excellent wear resistance under dry sliding condition.Both the primary phase(PP)and the laser-treated phase(LP)play pivotal roles in the wear performance of grey cast iron,in association with various combinations of PP and LP microhardness,originating from different laser processing and heat treatment.Owing to the optimized combination of microhardness,the result exhibits the dominant role of LP,with higher microhardness,in wear test,indicating that this technology,apart from producing complex structures,can also act as a design-process method to modify the tribological properties of grey cast iron,and thus providing a feasible approach to tailor the surface microhardness and to modify the wear performance of grey cast iron.Moreover,a threshold of wear resistance is obtained,while LP microhardness is above 900 HV;meanwhile,beyond it,the change of PP microhardness has only minor impact on wear performance.Finite element analysis shows that,in line with varying microhardness combination,distinct stress distribution on specimen surface is achieved,agreeing well with the good wear resistance and tailorable microhardness of LP and PP.
基金supported by the Development Plan of Shandong Province Young Innovation Team of Higher Education Institutions,China(No.2023KJ242)the National Natural Science Foundation of China(Nos.52371181,52101231,52101232,and 52175192)the Natural Science Foundation of Shandong Province,China(Nos.ZR2024QE019,and ZR2021QE044)。
文摘The external hard TiN ceramic layer and an internal reinforced NiTi matrix were controlled by combining nitriding and solution treatment to achieve ultra-high micro-hardness and excellent wear performance.In addition,the effects of nitriding and solution treatment on the microstructure evolution,martensitic transformation,and mechanical and functional properties of 60NiTi alloys were investigated.Compared with 60NiTi alloy,a harder TiN layer appeared at the surface of 60NiTi alloy with nitriding treatment.Meanwhile,a Ni_(3)Ti layer formed under the bottom of TiN layer owing to the consumption of Ti in matrix induced by formation of TiN layer.Upon undergoing solution treatment,the precipitates evolved from the coexistence of Ni_(3)Ti and Ni_(3)Ti_(2)phase to Ni_(4)Ti_(3)phase.The introduction of the outer harder TiN ceramic layer had a constraint of martensitic transformation of 60NiTi alloy,which led to the reduction of martensitic transformation temperature(Ms)and the suppression of martensitic transformation.Importantly,the construction of outermost harder TiN ceramic layer at the surface of B2-NiTi matrix enhanced Ni_(4)Ti_(3)phase improved significantly the microhardness and wear performances by the nitriding and followed solution treatment.Meanwhile,the high compressive fracture strength,fracture strain and superior superelasticity of 60NiTi alloy can be maintained.
基金Project(52174362)supported by the National Natural Science Foundation of ChinaProject(2023JJ10020)supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2024RC7002)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2024CY2-GJHX-71)supported by the Shaanxi Provincial Key R&D Program,ChinaProject supported by the Yancheng“Talent Plan of Yellow Sea Pearl”for Leading Talent Project,China。
文摘In this study,AZ31 Mg alloy sheets were processed by a severe plastic deformation(SPD)technique called forging-bending repeated deformation(FBRD).The effect on the microstructure and microhardness of AZ31 Mg alloy through FBRD was investigated with increasing temperature treatment and a 90°cross route.The results reveal that the effective strain increases with the number of passes.The flow uniformity is effectively enhanced due to alterations in shear deformation direction.After four passes of deformation,the average grain size is refined by 79.3%compared to the initial specimen.The grain refinement mechanism predominantly originates from the synergistic effects of discontinuous dynamic recrystallization(DDRX),continuous dynamic recrystallization(CDRX),and twinning-induced recrystallization(TDRX).The formation of{1012}extension twins(ET)significantly contributes to coarse grain subdivision and plastic deformation coordinated.Furthermore,pyramidal<c+a>slip activation effectively enhances the plasticity of Mg alloys.By post four-pass processing,the alloy exhibits a microhardness of 81.9HV,primarily governed by fine grain strengthening and dislocation strengthening mechanisms.
文摘A detailed investigation for the influence of post weld heat treatment （PWHT） on the microstructure of TC4 and TC17 dissimilar joints was analyzed. The fully transformed microstructure in the as-welded zone indicated that the peak temperature exceeded theβ-transus temperature at the weld interface during linear friction welding. TC4 side was mainly composed of martensiteα′phase with random distribution and it was singleβfor that of TC17. In the thermomechanically affected zones of TC4 and TC17, the structure undergoes severe plastic deformation and re-orientation, yet without altering the phase fractions. After PWHT, in the weld zone of TC4 alloy, the phase transformationα′→α＋βoccurred and the acicularαwas coarsened, which resulted in a decrease in hardness. In the weld zone of TC17 alloy, fineαphase precipitated at the grain boundary and withinβgrains, which resulted in a sharp increase in hardness.
基金Project(51071124)supported by the National Natural Science Foundation of ChinaProject(CX200605)supported by the Doctorate Foundation of Northwestern Polytechnical University,ChinaProject(20096102110012)supported by a Special Research Fund for Doctoral Disciplines in Colleges and Universities of the Ministry of Education,China
文摘Directionally solidified （DS） specimens of Nb-Ti-Si based ultrahigh temperature alloy were heat-treated at （1 500 ℃, 50 h） and （1 500 ℃, 50 h） ＋ （1 100 ℃, 50 h）, respectively. The results show that the microstructures become uniform, the long and big primary （Nb,X）sSi3 （X represents Ti and Hf elements） plates in the DS specimens are broken into small ones, and the eutectic cells lose their lamellar morphology and their interfaces become blurry after heat-treatment. Meanwhile, the （Nb,X）sSi3 slices in the eutectic cells of the DS specimens coarsen obviously after heat-treatment. Homogenizing and aging treatments could effectively eliminate elemental microsegregation, and the segregation ratios of all elements in niobium solid solution （Nbss） in different regions tend to 1. After heat-treatment, the microhardness of retained eutectic cells increases evidently, and the maximum value reaches HV1 404.57 for the specimen directionally solidified with a withdrawing rate of 100 μm/s and then heat-treated at （1 500 ℃, 50 h） ＋ （1 100 ℃, 50 h）, which is 72.8 % higher than that under DS condition.
基金Project(51374110)supported by the National Natural Science Foundation of ChinaProject(2015A030312003)supported by the Natural Science Foundation of Guangdong Province for Research Team,China
文摘The squeeze pressure field and power ultrasonic field were applied during the conventional casting process of Al-5.0Cu alloy simultaneously. The effects of individual squeeze pressure or power ultrasonic and their coupling on the microstructures and microhardness of Al-5.0Cu alloy were studied by optical microscopy, scanning electron microscopy, image analysis and micro Vickers hardness test. The results show that compared with the conventional casting, refined microstructures, homogeneous distribution of α（Al） and θ（Al2Cu） and improved microhardness can be obtained when squeeze pressure or power ultrasonic is applied individually. For the case of combined fields, both the treated region and the improvement of microstructure and properties can be enhanced.
基金Projects(51171091,51471099,51571132)supported by the National Natural Science Foundation of ChinaProject(2012CB825702)supported by the National Basic Research Program of China
文摘The thermal expansion behavior, microhardness and electrochemical corrosion resistance of Au52Cu27Ag17-x（NiZn0.5）x （x=0,6 and 12） alloys were investigated by dilatometer （DIL）, microhardness tester, electrochemical workstation, X-ray diffractometer（XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and X-ray photoelectron spectroscopy （XPS）.With increasing x, the relative length expansion and DIL maximum temperature Tl m （i.e., thermal stability） of the alloys increase inthermal expansion measurements, which can be explained by the change of the atomic binding energy, mismatch entropy togetherwith phase transformation. With the increase of x, the microhardness can be improved, but the corrosion resistance decreases; inaddition, the anodic peak current densities of polarization curves decrease, which are related closely with the solid solution degreeand dissolution of Ag, Ni and Zn alloying elements in Cl^- -containing solution.
基金Project(51875442)supported by the National Natural Science Foundation of China。
文摘The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in Ti6 Al4 V laser-welded joints with different welding speeds. The microhardness measured on the fusion line(H_m) is the highest from the weld center to the base metal. H_m increases with increasing weld width in a welded joint and increasing degree of the non-uniformity in all studied welded joints. The microhardness decreases from the weld metal to the base metal with decreasing amount of martensite α’ and increasing amount of original α phase. When the microstructure is mainly composed of martensite α’, the microhardness changes with the cooling rate, grain size of the martensite, and peak values of the fraction of misorientation angle of the martensite in a wide weld metal zone or weld center at different welding speeds, whereas the difference is small in a narrow weld metal zone.
基金Jian Cao,Gregory J.Wagner,and Wing K.Liu acknowledge support from the National Science Foundation(NSF)Cyber-Physical Systems(CPS)(CPS/CMMI-1646592)Hengyang Li acknowledges support from the Northwestern Data Science Initiative(DSI+6 种基金171474500210043324)Jian Cao,Gregory J.Wagner,Wing K.Liu,Jennifer L.Bennett,and Sarah J.Wolff acknowledge support from the Digital Manufacturing and Design Innovation Institute(DMDII15-07)Jian Cao,Wing K.Liu,Zhengtao Gan,and Jennifer L.Bennett acknowledge support from the Center for Hierarchical Materials Design(CHiMaD70NANB14H012)This work made use of facilities at DMG MORI and Northwestern UniversityIt also made use of the MatCI Facility,which receives support from the MRSEC Program(NSF DMR-168 1720139)of the Materials Research Center at Northwestern University.
文摘To design microstructure and microhardness in the additive manufacturing(AM)of nickel(Ni)-based superalloys,the present work develops a novel data-driven approach that combines physics-based models,experimental measurements,and a data-mining method.The simulation is based on a computational thermal-fluid dynamics(CtFD)model,which can obtain thermal behavior,solidification parameters such as cooling rate,and the dilution of solidified clad.Based on the computed thermal information,dendrite arm spacing and microhardness are estimated using well-tested mechanistic models.Experimental microstructure and microhardness are determined and compared with the simulated values for validation.To visualize process-structure-properties(PSPs)linkages,the simulation and experimental datasets are input to a data-mining model-a self-organizing map(SOM).The design windows of the process parameters under multiple objectives can be obtained from the visualized maps.The proposed approaches can be utilized in AM and other data-intensive processes.Data-driven linkages between process,structure,and properties have the potential to benefit online process monitoring control in order to derive an ideal microstructure and mechanical properties.
基金financially supported by the Youth Top Talents Research Project of Hebei Provincial Education Department China(No.BJ2018052)the Natural Science Foundation of Hebei Province of China(Nos.E2019208205 and E2018208126)+3 种基金the National Natural Science Foundation of China(No.51701064)the Science and Technology on Plasma Dynamics Laboratory Fund Project(No.614220206021806)the Key Research and Development Program of Hebei Province(No.19211016D)the Open Foundation of State Key Laboratory of Metastable Materials Science and Technology(Nos.201804 and 201812).
文摘The Ti-20Zr-6.5Al-4V(T20Z,wt%)alloy surface was treated by the process of laser surface nitriding.The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120 to 240 W.All laser-treated T20Z samples show two regions with distinctly different microstructural features,as compared with the untreated substrate:dense TiN dendrites and(α+β)-Ti(remelting zone,RMZ),nanoscaleαlaths doped with part of p phase(heat-affected zone,HAZ).The formation of TiN dendrites can be analyzed by a series of complex reactions during the process of melting and solidification.The increase in laser power results in the increase in content of TiN dendrite which is mainly due to the increase in energy input.In HAZ,the self-quenching effect leads to the formation of nanoscale a laths and the residue ofβphase.Microhardness profile of different regions was measured from the surface to the interior,and the highest microhardness was obtained(~HV 916.8)in the RMZ,as the laser power was set to 240 W.In the present study,we explained various microstructural characteristics induced by laser surface nitriding treatment.
基金the National Natural Science Foundation of China(Grant No.51361026)the Natural Science Foundation of Jiangxi Province(Grant No.20171BAB206006)+1 种基金the Key Project of Science and Technology Project of Jiangxi Provincial Education Department(Grant No.GJJ160678)Open Foundation of National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology,Nanchang Hangkong University(GF201501004).
文摘Severe plastic deformation of Ti-10V-2Fe-3Al alloy in the surface region was caused by shot peening at air pressure of 0.6 MPa with processing time ranging from 1 to 45 min.The results showed that the thickness of surface deformation layer was proportio nal to the processing time,the microhardness of the shot-peened surface in creased from 280 to 385 HV,and the depth of highly hardening layers arrived at 200μm.It was worth noting that a grain size gradient from nanocrystalline on the surface toward coarse grain in the matrix was obtained during the shot peening process and the minimum grain size in the top surface after shot peening was about 100-200 nm.
基金Projects(51875558,51471176)supported by the National Natural Science Foundation of ChinaProject(2017YFB1302802)supported by the National Key R&D Program of China。
文摘In this work,the nickel-based powder metallurgy superalloy FGH95 was selected as experimental material,and the experimental parameters in multiple overlap laser shock processing(LSP)treatment were selected based on orthogonal experimental design.The experimental data of residual stress and microhardness were measured in the same depth.The residual stress and microhardness laws were investigated and analyzed.Artificial neural network(ANN)with four layers(4-N-(N-1)-2)was applied to predict the residual stress and microhardness of FGH95 subjected to multiple overlap LSP.The experimental data were divided as training-testing sets in pairs.Laser energy,overlap rate,shocked times and depth were set as inputs,while residual stress and microhardness were set as outputs.The prediction performances with different network configuration of developed ANN models were compared and analyzed.The developed ANN model with network configuration of 4-7-6-2 showed the best predict performance.The predicted values showed a good agreement with the experimental values.In addition,the correlation coefficients among all the parameters and the effect of LSP parameters on materials response were studied.It can be concluded that ANN is a useful method to predict residual stress and microhardness of material subjected to LSP when with limited experimental data.
