Since processing parameters have always been assumed to be stable in the current finite element numerical simulation of dieless drawing process, the simulation results for the product dimension tend to stabilize gradu...Since processing parameters have always been assumed to be stable in the current finite element numerical simulation of dieless drawing process, the simulation results for the product dimension tend to stabilize gradually. In fact, the dimension fluctuation exists in the forming process all the while. A mathematical model of Gauss distribution for processing parameters was employed and a finite element numerical model of dieless drawing process with non-steady processing parameters was established. Dieless drawing processing of Ni-Ti alloy wire was conducted for verifying the proposed model. The results indicated that the non-steady processing parameters model had higher simulation accuracy of the wire diameter than that given by the steady parameters model. Furthermore, the model could also be used to analyze the fluctuation characteristics in the whole dieless drawing process.展开更多
Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation beh...Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation behavior and microstructure evolution of millimeter-grade coarse grains(MCGs)in the as-cast Ti-6Cr-5Mo-5V-4Al(Ti-6554)alloy were studied,and a hot processing map was established.Under compression along the rolling direction(RD),continuous dynamic recrystallization(CDRX)ensues due to the progressive rotation of subgrains within the MCGs.Along the transverse direction(TD),discontinuous dynamic recrystallization(DDRX)resulting from grain boundary bulging or bridging,occurs on the boundaries of the MCGs.With decreasing strain rate,increasing temperature,and higher deformation degree,dynamic recrystallization becomes more pronounced,resulting in a reduction in the original average grain size.The optimal processing parameters fall within a temperature range of 1050-1150℃,a strain rate of 0.01 s^(-1),and a deformation degree between 40%and 60%.展开更多
The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can caus...The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.展开更多
To overcome the shortage of complex equipment,large volume,and high energy consumption in space capsule manufacturing,a novel sliding pressure Joule heat fuse additive manufacturing technique with reduced volume and l...To overcome the shortage of complex equipment,large volume,and high energy consumption in space capsule manufacturing,a novel sliding pressure Joule heat fuse additive manufacturing technique with reduced volume and low energy consumption was proposed.But the unreasonable process parameters may lead to the inferior consistency of the forming quality of single-channel multilayer in Joule heat additive manufacturing process,and it is difficult to reach the condition for forming thinwalled parts.Orthogonal experiments were designed to fabricate single-channel multilayer samples with varying numbers of layers,and their forming quality was evaluated.The influence of printing current,forming speed,and contact pressure on the forming quality of the single-channel multilayer was analyzed.The optimal process parameters were obtained and the quality characterization of the experiment results was conducted.Results show that the printing current has the most significant influence on the forming quality of the single-channel multilayer.Under the optimal process parameters,the forming section is well fused and the surface is continuously smooth.The surface roughness of a single-channel 3-layer sample is 0.16μm,and the average Vickers hardness of cross section fusion zone is 317 HV,which lays a foundation for the subsequent use of Joule heat additive manufacturing technique to form thinwall parts.展开更多
The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average...The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.展开更多
To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceol...To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceolata) and poplar (triploid Populus tomentosa Carr) under different conditions was conducted. The results indicate that the residue rate decreases with the increase of liquefaction temperature, liquefaction time, catalyst content or liquid ratio. It is also found that the optimum condition of liquefaction for poplar is estimated as: the reaction temperature of 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4.5 and catalyst content of 8%, and 4.2% residue rate could be obtained. Under the processing parameters of temperature 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4 and catalyst content of 10%, the residue rate of Chinese fir can reach 5.6%.展开更多
Additive manufacturing(AM)has revolutionized modern manufacturing,but the application of magnesium(Mg)alloys in laser-based AM remains underexplored due to challenges such as oxidation,low boiling point,and thermal ex...Additive manufacturing(AM)has revolutionized modern manufacturing,but the application of magnesium(Mg)alloys in laser-based AM remains underexplored due to challenges such as oxidation,low boiling point,and thermal expansion,which lead to defects like porosity and cracking.This study provides a comprehensive analysis of microstructure changes in WE43 magnesium(Mg)alloy after laser surface melting(LSM),examining grain morphology,orientation,size,microsegregation,and defects under various combinations of laser power,scan speed,and spot size.Ourfindings reveal that variations in laser power and spot size exert a more significant influence on the depth and aspect ratio of the keyhole melt pool compared to laser scan speed.Critically,we demonstrate that laser energy density,while widely used as a quantitative metric to describe the combined effects of process parameters,exhibits significant limitations.Notable variations in melt pool depth,normalized width,and microstructure with laser energy density were observed,as reflected by low R²values.Additionally,we underscore the importance of assessing the temperature gradient across the width of the melt pool,which determines whether conduction or keyhole melting modes dominate.These modes exhibit distinct heatflow mechanisms and yield fundamentally different microstructural outcomes.Furthermore,we show that the microstructure and grain size in conduction mode exhibit a good correlation with the temperature gradient(G)and solidification rate(R).This research provides a framework for achieving localized microstructural control in LSM,providing insights to optimize process parameters for laser-based 3D printing of Mg alloys,and advancing the integration of Mg alloys into AM technologies.展开更多
As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet t...As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet transition are critical to high quality figuration. The effects of various processing parameters on figuration quality were studied in the experiment of GMA W rapid prototyping using the wire of ERSO-6 , including welding voltage, wire feeding rate, welding speed and so on. The optimal parameters for ERSO-6 are obtained. Simultaneously, it is verified that the rapid prototyping parts with favorable structures and quality can be achieved under the conditions of low heat input and stable droplet transition.展开更多
Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical ch...Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical challenges remain in the selective laser melting(SLM)fabrication of Ti-Zr-Cu alloy:First,the high thermal conductivity of the Cu element tends to destabilize the solidifcation behavior of the molten pool,leading to uncontrollable pore defect evolution;Second,the infuence of process parameters on the synergistic efects of zirconium solution strengthening and copper precipitation strengthening is not well understood,hindering precise control over the material's mechanical properties.To address these issues,this study systematically elucidates the quantitative impact of energy input on the defect formation mechanisms and strengthening efects in the SLM processing of Ti15Zr5Cu alloy.By optimizing laser power(120–200 W)and scanning speed(450–1200 mm/s)through a full-factor experimental design,we comprehensively analyze the efects of energy input on defect morphology,microstructure evolution,and mechanical performance.The results demonstrate that as energy density decreases,defect types transition from spherical pores to irregular pores,signifcantly infuencing mechanical properties.Based on the defect evolution trends,three distinct energy density regions are identifed:the high-energy region,the lowenergy region,and the transition region.Under the optimal processing conditions of a laser power of 180 W and a scanning speed of 1200 mm/s,the Ti15Zr5Cu alloy exhibits a relative density of 99.998%,a tensile strength of 1490±11 MPa,and an elongation at break of 6.0%±0.5%.These properties ensure that the material satisfes the stringent requirements for high strength in narrow-diameter implants used in the maxilloanterior region.This study provides theoretical and experimental support for the process-property optimization of Ti-Zr-Cu alloys in additive manufacturing and promotes their application in the fabrication of high-performance,antibacterial dental implants.展开更多
The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testin...The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testing was performed in various Zn and Mg contents under different annealing and cold-rolling conditions. In the results, the stress drop and reloading time of serrations increase with increasing plastic strain and exhibit a common linear relationship. The increase rates of stress drop and reloading time increase with increasing Mg or Zn content. The alloys with a greater intensity of serrated yielding generally exhibit a greater elongation. The stress drop and reloading time of serrations decrease with increasing grain size in the case of the annealed samples. The cold-rolled sample exhibits the most severe serra- tion because it initially contains a large number of grain boundaries and dislocations.展开更多
A neural network model of key process parameters and forming quality is developed based on training samples which are obtained from the orthogonal experiment and the finite element numerical simulation. Optimization o...A neural network model of key process parameters and forming quality is developed based on training samples which are obtained from the orthogonal experiment and the finite element numerical simulation. Optimization of the process parameters is conducted using the genetic algorithm (GA). The experimental results have shown that a surface model of the neural network can describe the nonlinear implicit relationship between the parameters of the power spinning process:the wall margin and amount of expansion. It has been found that the process of determining spinning technological parameters can be accelerated using the optimization method developed based on the BP neural network and the genetic algorithm used for the process parameters of power spinning formation. It is undoubtedly beneficial towards engineering applications.展开更多
Thin-walled aluminum alloy tube numerical control(NC)bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints.A significance-based optimization method of the ...Thin-walled aluminum alloy tube numerical control(NC)bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints.A significance-based optimization method of the parameters was proposed based on the finite element(FE)simulation,and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design.The optimum value of the significant parameter,the clearance between the tube and the wiper die,was obtained,and the values of the other parameters,including the friction coefficients and the clearances between the tube and the dies,the mandrel extension length and the boost velocity were estimated.The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm(initial tube outside diameter D0×initial tube wall thickness t0×bending radius R),and qualified tubes are produced.展开更多
The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying th...The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.展开更多
Silicone material extrusion(MEX)is widely used for processing liquids and pastes.Owing to the uneven linewidth and elastic extrusion deformation caused by material accumulation,products may exhibit geometric errors an...Silicone material extrusion(MEX)is widely used for processing liquids and pastes.Owing to the uneven linewidth and elastic extrusion deformation caused by material accumulation,products may exhibit geometric errors and performance defects,leading to a decline in product quality and affecting its service life.This study proposes a process parameter optimization method that considers the mechanical properties of printed specimens and production costs.To improve the quality of silicone printing samples and reduce production costs,three machine learning models,kernel extreme learning machine(KELM),support vector regression(SVR),and random forest(RF),were developed to predict these three factors.Training data were obtained through a complete factorial experiment.A new dataset is obtained using the Euclidean distance method,which assigns the elimination factor.It is trained with Bayesian optimization algorithms for parameter optimization,the new dataset is input into the improved double Gaussian extreme learning machine,and finally obtains the improved KELM model.The results showed improved prediction accuracy over SVR and RF.Furthermore,a multi-objective optimization framework was proposed by combining genetic algorithm technology with the improved KELM model.The effectiveness and reasonableness of the model algorithm were verified by comparing the optimized results with the experimental results.展开更多
Accelerating voltage,electron beam current,welding speed constitutes the main electron beam welding process parameters,while the penetration depth and depth-width ratio are two of the most important characteristic par...Accelerating voltage,electron beam current,welding speed constitutes the main electron beam welding process parameters,while the penetration depth and depth-width ratio are two of the most important characteristic parameters of the weld geometries.However complex interactions exists between the five variables,so the analysis of a single process parameter on one of weld geometries is affected by the other process parameters,and the impact of these interference parameters should be excluded to find the real relationship between the variables where partial correlation analysis provides such a method.Effects of the accelerating voltage,electron beam current,welding speed of electron beam welding process parameters on weld geometries is analyzed by using partial correlation analysis.The priority order of adjustment of process parameters is obtained,namely:in order to obtain a larger depth-width ratio indicators,it should be taken firstly to increase the beam current and accelerating voltage,and then to raise the welding speed;in order to obtain greater penetration depth,it is preferred to increase the beam current,followed by increasing the accelerating voltage,and reducing the welding speed finally.展开更多
The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of th...The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.展开更多
Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot ...Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.展开更多
Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to pr...Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to produce porous Mg degradable implants.However,the microstructure evolution and mechanical properties of the SLMed NZ30K Mg alloy were not yet studied systematically.Therefore,the fabrication defects,microstructure,and mechanical properties of the SLMed NZ30K alloy under different processing parameters were investigated.The results show that there are two types of fabrication defects in the SLMed NZ30K alloy,gas pores and unfused defects.With the increase of the laser energy density,the porosity sharply decreases to the minimum first and then slightly increases.The minimum porosity is 0.49±0.18%.While the microstructure varies from the large grains with lamellar structure inside under low laser energy density,to the large grains with lamellar structure inside&the equiaxed grains&the columnar grains under middle laser energy density,and further to the fine equiaxed grains&the columnar grains under high laser energy density.The lamellar structure in the large grain is a newly observed microstructure for the NZ30K Mg alloy.Higher laser energy density leads to finer grains,which enhance all the yield strength(YS),ultimate tensile strength(UTS)and elongation,and the best comprehensive mechanical properties obtained are YS of 266±2.1 MPa,UTS of 296±5.2 MPa,with an elongation of 4.9±0.68%.The SLMed NZ30K Mg alloy with a bimodal-grained structure consisting of fine equiaxed grains and coarser columnar grains has better elongation and a yield drop phenomenon.展开更多
Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained co...Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.展开更多
基金National Basic Research Program of China (2006CB605200)National Natural Science Foundation of China (50634010, 50674008)Program for New Century Excellent Talents in University (NCET-06-0083)
文摘Since processing parameters have always been assumed to be stable in the current finite element numerical simulation of dieless drawing process, the simulation results for the product dimension tend to stabilize gradually. In fact, the dimension fluctuation exists in the forming process all the while. A mathematical model of Gauss distribution for processing parameters was employed and a finite element numerical model of dieless drawing process with non-steady processing parameters was established. Dieless drawing processing of Ni-Ti alloy wire was conducted for verifying the proposed model. The results indicated that the non-steady processing parameters model had higher simulation accuracy of the wire diameter than that given by the steady parameters model. Furthermore, the model could also be used to analyze the fluctuation characteristics in the whole dieless drawing process.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3706901,2022YFB3706903)the National Natural Science Foundation of China(No.52274382)。
文摘Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation behavior and microstructure evolution of millimeter-grade coarse grains(MCGs)in the as-cast Ti-6Cr-5Mo-5V-4Al(Ti-6554)alloy were studied,and a hot processing map was established.Under compression along the rolling direction(RD),continuous dynamic recrystallization(CDRX)ensues due to the progressive rotation of subgrains within the MCGs.Along the transverse direction(TD),discontinuous dynamic recrystallization(DDRX)resulting from grain boundary bulging or bridging,occurs on the boundaries of the MCGs.With decreasing strain rate,increasing temperature,and higher deformation degree,dynamic recrystallization becomes more pronounced,resulting in a reduction in the original average grain size.The optimal processing parameters fall within a temperature range of 1050-1150℃,a strain rate of 0.01 s^(-1),and a deformation degree between 40%and 60%.
基金Projects(U22B2084,52275483,52075142)supported by the National Natural Science Foundation of ChinaProject(2023ZY01050)supported by the Ministry of Industry and Information Technology High Quality Development,China。
文摘The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.
基金Shaanxi Province Qin Chuangyuan“Scientist+Engineer”Team Construction Project(2022KXJ-071)2022 Qin Chuangyuan Achievement Transformation Incubation Capacity Improvement Project(2022JH-ZHFHTS-0012)+1 种基金Shaanxi Province Key Research and Development Plan-“Two Chains”Integration Key Project-Qin Chuangyuan General Window Industrial Cluster Project(2023QCY-LL-02)Xixian New Area Science and Technology Plan(2022-YXYJ-003,2022-XXCY-010)。
文摘To overcome the shortage of complex equipment,large volume,and high energy consumption in space capsule manufacturing,a novel sliding pressure Joule heat fuse additive manufacturing technique with reduced volume and low energy consumption was proposed.But the unreasonable process parameters may lead to the inferior consistency of the forming quality of single-channel multilayer in Joule heat additive manufacturing process,and it is difficult to reach the condition for forming thinwalled parts.Orthogonal experiments were designed to fabricate single-channel multilayer samples with varying numbers of layers,and their forming quality was evaluated.The influence of printing current,forming speed,and contact pressure on the forming quality of the single-channel multilayer was analyzed.The optimal process parameters were obtained and the quality characterization of the experiment results was conducted.Results show that the printing current has the most significant influence on the forming quality of the single-channel multilayer.Under the optimal process parameters,the forming section is well fused and the surface is continuously smooth.The surface roughness of a single-channel 3-layer sample is 0.16μm,and the average Vickers hardness of cross section fusion zone is 317 HV,which lays a foundation for the subsequent use of Joule heat additive manufacturing technique to form thinwall parts.
基金supported by the National Natural Science Foundation of China (No. 50274021)
文摘The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.
基金Supported by the Key Research Program Foundation of Ministry of Education of China (Grant No.02021) and the Development Plan Foundation of Beijing Forestry University
文摘To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceolata) and poplar (triploid Populus tomentosa Carr) under different conditions was conducted. The results indicate that the residue rate decreases with the increase of liquefaction temperature, liquefaction time, catalyst content or liquid ratio. It is also found that the optimum condition of liquefaction for poplar is estimated as: the reaction temperature of 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4.5 and catalyst content of 8%, and 4.2% residue rate could be obtained. Under the processing parameters of temperature 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4 and catalyst content of 10%, the residue rate of Chinese fir can reach 5.6%.
文摘Additive manufacturing(AM)has revolutionized modern manufacturing,but the application of magnesium(Mg)alloys in laser-based AM remains underexplored due to challenges such as oxidation,low boiling point,and thermal expansion,which lead to defects like porosity and cracking.This study provides a comprehensive analysis of microstructure changes in WE43 magnesium(Mg)alloy after laser surface melting(LSM),examining grain morphology,orientation,size,microsegregation,and defects under various combinations of laser power,scan speed,and spot size.Ourfindings reveal that variations in laser power and spot size exert a more significant influence on the depth and aspect ratio of the keyhole melt pool compared to laser scan speed.Critically,we demonstrate that laser energy density,while widely used as a quantitative metric to describe the combined effects of process parameters,exhibits significant limitations.Notable variations in melt pool depth,normalized width,and microstructure with laser energy density were observed,as reflected by low R²values.Additionally,we underscore the importance of assessing the temperature gradient across the width of the melt pool,which determines whether conduction or keyhole melting modes dominate.These modes exhibit distinct heatflow mechanisms and yield fundamentally different microstructural outcomes.Furthermore,we show that the microstructure and grain size in conduction mode exhibit a good correlation with the temperature gradient(G)and solidification rate(R).This research provides a framework for achieving localized microstructural control in LSM,providing insights to optimize process parameters for laser-based 3D printing of Mg alloys,and advancing the integration of Mg alloys into AM technologies.
文摘As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet transition are critical to high quality figuration. The effects of various processing parameters on figuration quality were studied in the experiment of GMA W rapid prototyping using the wire of ERSO-6 , including welding voltage, wire feeding rate, welding speed and so on. The optimal parameters for ERSO-6 are obtained. Simultaneously, it is verified that the rapid prototyping parts with favorable structures and quality can be achieved under the conditions of low heat input and stable droplet transition.
基金supported by the National Natural Science Foundation of China(Nos.52401178 and U24A20713)the IMR Innovation Fund(No.2024-PY06)the CAS-WEGO Research and Development Plan Project.
文摘Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical challenges remain in the selective laser melting(SLM)fabrication of Ti-Zr-Cu alloy:First,the high thermal conductivity of the Cu element tends to destabilize the solidifcation behavior of the molten pool,leading to uncontrollable pore defect evolution;Second,the infuence of process parameters on the synergistic efects of zirconium solution strengthening and copper precipitation strengthening is not well understood,hindering precise control over the material's mechanical properties.To address these issues,this study systematically elucidates the quantitative impact of energy input on the defect formation mechanisms and strengthening efects in the SLM processing of Ti15Zr5Cu alloy.By optimizing laser power(120–200 W)and scanning speed(450–1200 mm/s)through a full-factor experimental design,we comprehensively analyze the efects of energy input on defect morphology,microstructure evolution,and mechanical performance.The results demonstrate that as energy density decreases,defect types transition from spherical pores to irregular pores,signifcantly infuencing mechanical properties.Based on the defect evolution trends,three distinct energy density regions are identifed:the high-energy region,the lowenergy region,and the transition region.Under the optimal processing conditions of a laser power of 180 W and a scanning speed of 1200 mm/s,the Ti15Zr5Cu alloy exhibits a relative density of 99.998%,a tensile strength of 1490±11 MPa,and an elongation at break of 6.0%±0.5%.These properties ensure that the material satisfes the stringent requirements for high strength in narrow-diameter implants used in the maxilloanterior region.This study provides theoretical and experimental support for the process-property optimization of Ti-Zr-Cu alloys in additive manufacturing and promotes their application in the fabrication of high-performance,antibacterial dental implants.
基金financially supported by the National Natural Science Foundation of China(No.51301017)the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-13-034A)
文摘The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testing was performed in various Zn and Mg contents under different annealing and cold-rolling conditions. In the results, the stress drop and reloading time of serrations increase with increasing plastic strain and exhibit a common linear relationship. The increase rates of stress drop and reloading time increase with increasing Mg or Zn content. The alloys with a greater intensity of serrated yielding generally exhibit a greater elongation. The stress drop and reloading time of serrations decrease with increasing grain size in the case of the annealed samples. The cold-rolled sample exhibits the most severe serra- tion because it initially contains a large number of grain boundaries and dislocations.
基金Supported by the Natural Science Foundation of Shanxi Province Project(2012011023-2)
文摘A neural network model of key process parameters and forming quality is developed based on training samples which are obtained from the orthogonal experiment and the finite element numerical simulation. Optimization of the process parameters is conducted using the genetic algorithm (GA). The experimental results have shown that a surface model of the neural network can describe the nonlinear implicit relationship between the parameters of the power spinning process:the wall margin and amount of expansion. It has been found that the process of determining spinning technological parameters can be accelerated using the optimization method developed based on the BP neural network and the genetic algorithm used for the process parameters of power spinning formation. It is undoubtedly beneficial towards engineering applications.
基金Projects(50905144,50875216)supported by the National Natural Science Foundation of ChinaProject(09-10)supported by the State Key Laboratory of Materials Processing and Die&Mould Technology,ChinaProject(JC201028)supported by the Northwestern Polytechnical University Foundation for Fundamental Research,China
文摘Thin-walled aluminum alloy tube numerical control(NC)bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints.A significance-based optimization method of the parameters was proposed based on the finite element(FE)simulation,and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design.The optimum value of the significant parameter,the clearance between the tube and the wiper die,was obtained,and the values of the other parameters,including the friction coefficients and the clearances between the tube and the dies,the mandrel extension length and the boost velocity were estimated.The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm(initial tube outside diameter D0×initial tube wall thickness t0×bending radius R),and qualified tubes are produced.
基金the Tertiary Education Support Program (TESP) of ESKOM for financial support
文摘The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.
基金supported by the National Key R&D Program of China(No.2022YFA1005204l)。
文摘Silicone material extrusion(MEX)is widely used for processing liquids and pastes.Owing to the uneven linewidth and elastic extrusion deformation caused by material accumulation,products may exhibit geometric errors and performance defects,leading to a decline in product quality and affecting its service life.This study proposes a process parameter optimization method that considers the mechanical properties of printed specimens and production costs.To improve the quality of silicone printing samples and reduce production costs,three machine learning models,kernel extreme learning machine(KELM),support vector regression(SVR),and random forest(RF),were developed to predict these three factors.Training data were obtained through a complete factorial experiment.A new dataset is obtained using the Euclidean distance method,which assigns the elimination factor.It is trained with Bayesian optimization algorithms for parameter optimization,the new dataset is input into the improved double Gaussian extreme learning machine,and finally obtains the improved KELM model.The results showed improved prediction accuracy over SVR and RF.Furthermore,a multi-objective optimization framework was proposed by combining genetic algorithm technology with the improved KELM model.The effectiveness and reasonableness of the model algorithm were verified by comparing the optimized results with the experimental results.
文摘Accelerating voltage,electron beam current,welding speed constitutes the main electron beam welding process parameters,while the penetration depth and depth-width ratio are two of the most important characteristic parameters of the weld geometries.However complex interactions exists between the five variables,so the analysis of a single process parameter on one of weld geometries is affected by the other process parameters,and the impact of these interference parameters should be excluded to find the real relationship between the variables where partial correlation analysis provides such a method.Effects of the accelerating voltage,electron beam current,welding speed of electron beam welding process parameters on weld geometries is analyzed by using partial correlation analysis.The priority order of adjustment of process parameters is obtained,namely:in order to obtain a larger depth-width ratio indicators,it should be taken firstly to increase the beam current and accelerating voltage,and then to raise the welding speed;in order to obtain greater penetration depth,it is preferred to increase the beam current,followed by increasing the accelerating voltage,and reducing the welding speed finally.
文摘The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.
基金financially supported by the National Key Research and Development Program of China(Grant No.2020YFB2008300)。
文摘Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.
基金financial supports from the National Natural Science Foundation of China(52130104,51821001)High Technology and Key Development Project of Ningbo,China(2019B10102)。
文摘Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to produce porous Mg degradable implants.However,the microstructure evolution and mechanical properties of the SLMed NZ30K Mg alloy were not yet studied systematically.Therefore,the fabrication defects,microstructure,and mechanical properties of the SLMed NZ30K alloy under different processing parameters were investigated.The results show that there are two types of fabrication defects in the SLMed NZ30K alloy,gas pores and unfused defects.With the increase of the laser energy density,the porosity sharply decreases to the minimum first and then slightly increases.The minimum porosity is 0.49±0.18%.While the microstructure varies from the large grains with lamellar structure inside under low laser energy density,to the large grains with lamellar structure inside&the equiaxed grains&the columnar grains under middle laser energy density,and further to the fine equiaxed grains&the columnar grains under high laser energy density.The lamellar structure in the large grain is a newly observed microstructure for the NZ30K Mg alloy.Higher laser energy density leads to finer grains,which enhance all the yield strength(YS),ultimate tensile strength(UTS)and elongation,and the best comprehensive mechanical properties obtained are YS of 266±2.1 MPa,UTS of 296±5.2 MPa,with an elongation of 4.9±0.68%.The SLMed NZ30K Mg alloy with a bimodal-grained structure consisting of fine equiaxed grains and coarser columnar grains has better elongation and a yield drop phenomenon.
文摘Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.
