With the aim to improve the strength of Al-Zn-Mg-Cu alloy,the alloy billet containing Mn was produced by spray forming method,and the microstructural features were investigated using X-ray diffraction（XRD）,optical m...With the aim to improve the strength of Al-Zn-Mg-Cu alloy,the alloy billet containing Mn was produced by spray forming method,and the microstructural features were investigated using X-ray diffraction（XRD）,optical microscopy（OM）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）.The results show that the billet mainly consists of fine equiaxial grains of MgZn2 and Al6Mn with size ranging from 5 μm to 25 μm.Nano-scaled MgZn2 is dispersed in the as-sprayed alloy,primary Al6Mn particles are precipitated at grain boundaries with an average size of 5 μm.A few CuAl2,Al3Zr and eutectic are also found in as-sprayed Al alloy.The volume fraction of the porosity is about 12%.DSC result indicates that most of the solutes are precipitated during spray forming process,and no obviously thermal effects occur below 450 ℃.Both matrix grains and Al6Mn particles grow monotonously with the increase of annealing temperature,but the growth rate of Al6Mn particles is markedly lower than that of Al grains,and the matrix grains grow rapidly when the annealing temperature is above 375 ℃.展开更多
Based on the Newtonian heat transfer formulation and classical heterogeneous nucleation theory, a mathematical model has been established to predict the profile of flight velocity, heat transfer coefficient, temperat...Based on the Newtonian heat transfer formulation and classical heterogeneous nucleation theory, a mathematical model has been established to predict the profile of flight velocity, heat transfer coefficient, temperature, solid fraction and cooling rate of atomizing droplets for a superalloy. The results indicated that above parameters change with different droplet size and flight distance. The changing trend as well as the mechanism for the change are described and discussed.展开更多
The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0...The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.展开更多
Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7 xxx alloys. ...Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7 xxx alloys. The 7050 alloy machining chips were spray formed, hot extruded, rotary swaged and heat-treated in order to improve mechanical properties. Microstructures, tensile properties and fatigue strength results for a 2.7 mm-diameter recycled wire are presented. Secondary phases and precipitates were investigated by XRD, SEM, EBSD, TEM and DSC. As-swaged and heat-treated(solution and aging) conditions were evaluated. Mechanical properties of both conditions outperformed AA7050 aerospace specification. Substantial grain refinement resulted from the extensive plastic deformation imposed by rotary swaging. Refined micrometric and sub-micrometric Al grains, as well as coarse and fine intermetallic precipitates were observed. Subsequent solution treatment resulted in a homogeneous, recrystallized and equiaxed microstructure with grain size of 9 μm. Nanoscale GP(I) zones and η′ phase precipitates formed after aging at 120 ℃, imparting higher tensile(586 MPa) and fatigue(198 MPa) strengths.展开更多
The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted...The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.展开更多
High strength Al Zn Mg Cu alloys were produced by spray forming process, and compacted by hot extrusion. The results show that the as deposited billets have fine grained microstructure and low porosity. After heat tre...High strength Al Zn Mg Cu alloys were produced by spray forming process, and compacted by hot extrusion. The results show that the as deposited billets have fine grained microstructure and low porosity. After heat treatment, mechanical properties increase greatly: tensile strength up to 754 MPa, yield strength up to 722 MPa, fracture elongation up to 8%, and elastic modulus up to 72 GPa, respectively. [展开更多
The metal spray forming process was examined using the mathematical model simulation by Baosteel＇s test and developed facilities.The mathematical model comprised of the probability and statistical analysis of the dro...The metal spray forming process was examined using the mathematical model simulation by Baosteel＇s test and developed facilities.The mathematical model comprised of the probability and statistical analysis of the droplet mass behavior and predicted the shape and temperature distribution of the billet during the spray forming process.展开更多
The mechanical properties and microstructure characteristics of a high speed steel (HSS) for roll has been studied. As compared with the as-cast HSS, the spray-formed HSS have fine grain and segregation free microstru...The mechanical properties and microstructure characteristics of a high speed steel (HSS) for roll has been studied. As compared with the as-cast HSS, the spray-formed HSS have fine grain and segregation free microstructures. Carbides distribute uniformly. The morphology and types of the carbides in spray-formed HSS are different from those in as-cast HSS. The results of the high temperature tensile experiment show that, as to spray-formed HSS, there is a possibility of superplastic deformation in the range of 780-810℃.展开更多
In order to study the hot workability and to optimize the processing parameters for spray formed FGH4095 superalloy, thermal compression tests for spray formed FGH4095 superalloy have been finished by using a Gleeble ...In order to study the hot workability and to optimize the processing parameters for spray formed FGH4095 superalloy, thermal compression tests for spray formed FGH4095 superalloy have been finished by using a Gleeble 1500 thermal simulated test machine at the strain rates of 0.01-10.0 s 1 and temperatures of 1 050-1 140 ℃. The effects of strain rate and deformation temperature on the true stress-true strain curves and microstructure evolution were investigated. The results show that the generation of dynamic recrystallization （DRX） depends sensitively on deformation temperature. When the temperature was lower than 1080 ~C, long and＂ narrow necklace grains were shown in the microstructure. When the temperature increased to 1 140 ℃, new recrystallization grains were genera-ted. The size and shape of X＇ precipitates in the grains have a very important effect as factors of hindering sufficient migration of dislocations on plastic deformation. The result of thermal processing map is in accord with the micro-structure observation, and the best material thermal processing temperature is above 1 128 ℃.展开更多
A new process consisting of the spray forming and the continuous extrusion forming for manufacturing 7075A1 alloy was proposed. The microstructure evolution, mechanical properties and the resistance to stress corrosio...A new process consisting of the spray forming and the continuous extrusion forming for manufacturing 7075A1 alloy was proposed. The microstructure evolution, mechanical properties and the resistance to stress corrosion cracking of the alloy were studied. The results indicate that the spray forming process induces obviously grain refinement and greatly lower segregation microstructure. Besides, the Conform process produces finer grains and conduces to more uniform distribution of the precipitates of A1Cu and MgZn2 phases. The fabricated alloy shows good comprehensive mechanical properties and superb performance of stress corrosion resistance. Moreover, a better combination of the mechanical properties and the resistance to stress corrosion cracking could then be obtained under a certain condition of atomization gas pressure of 0.19 MPa. The enhanced properties are attributed to the following factors, which include the grain refinement, the fine and homogeneous distribution of A1Cu and MgZn2 phases, the high density of the extruded products, as well as the discontinuous distribution of the grain boundaries after retrogression and reaging （RRA） heat treatment.展开更多
The grain growth behavior in reactive spray formed 7075+2.91 vol percent TiCAl alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. Theeffects of in-situ TiC particles on the mic...The grain growth behavior in reactive spray formed 7075+2.91 vol percent TiCAl alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. Theeffects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were alsoinvestigated. The specimens were heat-treated isothermally at various temperatures between thesolidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water.The microstructure of reheated specimens was characterized using scanning electron microscopy andoptical microscopy. The grain size was measured using a mean linear intercept method. Results showthat the in-situ TiC particles can effectively retard grain growth and refine the grain at a limitedsize. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates thatthe in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solidstate.展开更多
Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content （Cu-13.5 wt pct Sn） was...Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content （Cu-13.5 wt pct Sn） was prepared successfully by spray forming, the feasibility of cold roiling this alloy was investigated, and the cold roiling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-roiled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties. Particularly, it shows a low elastic modulus （-88 GPa） and a high flow stress （over 800 MPa） after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.展开更多
A model for simulating the spray forming process with scanning atomizer was developed.Models for the scanning atomization and the deposition processes were coupled together in order to obtain a new description of the ...A model for simulating the spray forming process with scanning atomizer was developed.Models for the scanning atomization and the deposition processes were coupled together in order to obtain a new description of the spray forming process.The model,which is able to predict the shape of a spray-formed billet prepared with scanning atomizer,was established after analyzing the changes in droplet size and density distribution along the r-axis in the spray cone in scanning atomization.The effects of the two kinds of atomization were compared,showing that the scanning atomization is good for deposition.展开更多
The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation tem...The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the swain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.展开更多
A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstruct...A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.展开更多
In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamic...In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamics approach is developed to describe the microstructure evolution under the common action of the nucleation and growth of grains. The model is coupled with droplets heat transfer controlling equations and solved for AI-4.5 wt pct Cu alloy. It is demonstrated that the numerical results describe the solidification process well.展开更多
The deformation mechanism of the spray formed 70Si30Al alloy was studied by hot compression on a Gleeble-1500 test machine. It is shown that hot deformation of the spray formed 70Si30Al alloy is achieved by liquid flo...The deformation mechanism of the spray formed 70Si30Al alloy was studied by hot compression on a Gleeble-1500 test machine. It is shown that hot deformation of the spray formed 70Si30Al alloy is achieved by liquid flow due to isostatic pressure and movement of solid particles due to shear force. Deformation condition depends on the nucleation rate and closure rate of the cavities. The flow stress slightly varies when the difference between the nucleation rate and closure rate of the cavities is small; however, it decreases when the nucleation rate of the cavities is greater than the closure rate of the cavities.展开更多
The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sect...The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sections, including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior, and forecast of the shape and temperature distribution of the billet during the spray forming process.展开更多
Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. ...Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. 001-10 s^（-1）. A comprehensive constitutive equation was obtained,which could be used to predict the flow stress at different strains. Processing map was developed on the basis of the flow stress data using the principles of dynamic material model. The results showed that the flow curves were in fair agreement with the dynamic recrystallization model. The flow stresses,which were calculated by the comprehensive constitutive equation,agreed well with the test data at low strain rates（ ≤1 s^（-1））. The material constant（ α）,stress exponent（ n） and the hot deformation activation energy（ Q_（HW）） of the new steel were 0. 006 15 MPa^（-1）,4. 81 and 546 kJ·mol^（-1）,respectively. Analysis of the processing map with an observation of microstructures revealed that hot working processes of the steel could be carried out safely in the domain（ T = 1 050-1 150 ℃,ε = 0. 01- 0. 1 s^（-1））with about 33% peak efficiency of power dissipation（ η）. Cracks was expected in two domains at either lower temperatures（ 〈 1 000 ℃） or low strain rates（ 0. 001 s^（-1）） with different cracking mechanisms. Flow localization occurred when the strain rates exceeded 1 s^（-1） at all testing temperatures.展开更多
The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerabl...The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed grains.The measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are analyzed.Also,effects of heat treatment on microstructure were discussed.The results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the microstructure.Regarding processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.展开更多
基金Project(2006CB605204) supported by the National Basic Research Program of China
文摘With the aim to improve the strength of Al-Zn-Mg-Cu alloy,the alloy billet containing Mn was produced by spray forming method,and the microstructural features were investigated using X-ray diffraction（XRD）,optical microscopy（OM）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）.The results show that the billet mainly consists of fine equiaxial grains of MgZn2 and Al6Mn with size ranging from 5 μm to 25 μm.Nano-scaled MgZn2 is dispersed in the as-sprayed alloy,primary Al6Mn particles are precipitated at grain boundaries with an average size of 5 μm.A few CuAl2,Al3Zr and eutectic are also found in as-sprayed Al alloy.The volume fraction of the porosity is about 12%.DSC result indicates that most of the solutes are precipitated during spray forming process,and no obviously thermal effects occur below 450 ℃.Both matrix grains and Al6Mn particles grow monotonously with the increase of annealing temperature,but the growth rate of Al6Mn particles is markedly lower than that of Al grains,and the matrix grains grow rapidly when the annealing temperature is above 375 ℃.
文摘Based on the Newtonian heat transfer formulation and classical heterogeneous nucleation theory, a mathematical model has been established to predict the profile of flight velocity, heat transfer coefficient, temperature, solid fraction and cooling rate of atomizing droplets for a superalloy. The results indicated that above parameters change with different droplet size and flight distance. The changing trend as well as the mechanism for the change are described and discussed.
基金the support from the National Natural Science Foundation of China(No.52271177)the Science and Technology Innovation Leaders Projects in Hunan Province,China(No.2021RC4036).
文摘The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.
基金supported by CAPES, FINEP (FINEP/CTENERG: 01.09.0485.00)a FAPESP Project (2013/05987-8)a BPE grant awarded to C.R.M. Afonso (2015/19978-6)
文摘Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7 xxx alloys. The 7050 alloy machining chips were spray formed, hot extruded, rotary swaged and heat-treated in order to improve mechanical properties. Microstructures, tensile properties and fatigue strength results for a 2.7 mm-diameter recycled wire are presented. Secondary phases and precipitates were investigated by XRD, SEM, EBSD, TEM and DSC. As-swaged and heat-treated(solution and aging) conditions were evaluated. Mechanical properties of both conditions outperformed AA7050 aerospace specification. Substantial grain refinement resulted from the extensive plastic deformation imposed by rotary swaging. Refined micrometric and sub-micrometric Al grains, as well as coarse and fine intermetallic precipitates were observed. Subsequent solution treatment resulted in a homogeneous, recrystallized and equiaxed microstructure with grain size of 9 μm. Nanoscale GP(I) zones and η′ phase precipitates formed after aging at 120 ℃, imparting higher tensile(586 MPa) and fatigue(198 MPa) strengths.
文摘The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.
文摘High strength Al Zn Mg Cu alloys were produced by spray forming process, and compacted by hot extrusion. The results show that the as deposited billets have fine grained microstructure and low porosity. After heat treatment, mechanical properties increase greatly: tensile strength up to 754 MPa, yield strength up to 722 MPa, fracture elongation up to 8%, and elastic modulus up to 72 GPa, respectively. [
基金Item Sponsored by the NSFC and the Baoshan Steel Complex of Shanghai,the Joint Fund of Iron and Steel Research(50474082)
文摘The metal spray forming process was examined using the mathematical model simulation by Baosteel＇s test and developed facilities.The mathematical model comprised of the probability and statistical analysis of the droplet mass behavior and predicted the shape and temperature distribution of the billet during the spray forming process.
文摘The mechanical properties and microstructure characteristics of a high speed steel (HSS) for roll has been studied. As compared with the as-cast HSS, the spray-formed HSS have fine grain and segregation free microstructures. Carbides distribute uniformly. The morphology and types of the carbides in spray-formed HSS are different from those in as-cast HSS. The results of the high temperature tensile experiment show that, as to spray-formed HSS, there is a possibility of superplastic deformation in the range of 780-810℃.
基金Item Sponsored by National Natural Science Foundation of China ( 50974016 )
文摘In order to study the hot workability and to optimize the processing parameters for spray formed FGH4095 superalloy, thermal compression tests for spray formed FGH4095 superalloy have been finished by using a Gleeble 1500 thermal simulated test machine at the strain rates of 0.01-10.0 s 1 and temperatures of 1 050-1 140 ℃. The effects of strain rate and deformation temperature on the true stress-true strain curves and microstructure evolution were investigated. The results show that the generation of dynamic recrystallization （DRX） depends sensitively on deformation temperature. When the temperature was lower than 1080 ~C, long and＂ narrow necklace grains were shown in the microstructure. When the temperature increased to 1 140 ℃, new recrystallization grains were genera-ted. The size and shape of X＇ precipitates in the grains have a very important effect as factors of hindering sufficient migration of dislocations on plastic deformation. The result of thermal processing map is in accord with the micro-structure observation, and the best material thermal processing temperature is above 1 128 ℃.
基金supported by the National Natural Science Foundation (508740655)Yunnan Province Natural Science Foundation (2007E0013Z)
文摘A new process consisting of the spray forming and the continuous extrusion forming for manufacturing 7075A1 alloy was proposed. The microstructure evolution, mechanical properties and the resistance to stress corrosion cracking of the alloy were studied. The results indicate that the spray forming process induces obviously grain refinement and greatly lower segregation microstructure. Besides, the Conform process produces finer grains and conduces to more uniform distribution of the precipitates of A1Cu and MgZn2 phases. The fabricated alloy shows good comprehensive mechanical properties and superb performance of stress corrosion resistance. Moreover, a better combination of the mechanical properties and the resistance to stress corrosion cracking could then be obtained under a certain condition of atomization gas pressure of 0.19 MPa. The enhanced properties are attributed to the following factors, which include the grain refinement, the fine and homogeneous distribution of A1Cu and MgZn2 phases, the high density of the extruded products, as well as the discontinuous distribution of the grain boundaries after retrogression and reaging （RRA） heat treatment.
基金This work was financially supported by the National Natural Science Foundation of China (No.50171010)
文摘The grain growth behavior in reactive spray formed 7075+2.91 vol percent TiCAl alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. Theeffects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were alsoinvestigated. The specimens were heat-treated isothermally at various temperatures between thesolidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water.The microstructure of reheated specimens was characterized using scanning electron microscopy andoptical microscopy. The grain size was measured using a mean linear intercept method. Results showthat the in-situ TiC particles can effectively retard grain growth and refine the grain at a limitedsize. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates thatthe in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solidstate.
基金the Hundred-Talent-Person Project of Chinese Academy of Sciences.
文摘Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content （Cu-13.5 wt pct Sn） was prepared successfully by spray forming, the feasibility of cold roiling this alloy was investigated, and the cold roiling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-roiled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties. Particularly, it shows a low elastic modulus （-88 GPa） and a high flow stress （over 800 MPa） after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.
基金financially supported by Program of 863 Project(No 2006AA03Z114)Programon National Key Laboratory Foundation(No 9140C500101060C50)
文摘A model for simulating the spray forming process with scanning atomizer was developed.Models for the scanning atomization and the deposition processes were coupled together in order to obtain a new description of the spray forming process.The model,which is able to predict the shape of a spray-formed billet prepared with scanning atomizer,was established after analyzing the changes in droplet size and density distribution along the r-axis in the spray cone in scanning atomization.The effects of the two kinds of atomization were compared,showing that the scanning atomization is good for deposition.
基金This work was financially supported by the National Basic Research Program of China (No. G20000672).
文摘The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the swain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.
基金This study was financially supported by the National Basic Research Program of China (G20000672)
文摘A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.
文摘In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamics approach is developed to describe the microstructure evolution under the common action of the nucleation and growth of grains. The model is coupled with droplets heat transfer controlling equations and solved for AI-4.5 wt pct Cu alloy. It is demonstrated that the numerical results describe the solidification process well.
基金This study was financially supported by the National Basic Research Program of China (No. G20000672).
文摘The deformation mechanism of the spray formed 70Si30Al alloy was studied by hot compression on a Gleeble-1500 test machine. It is shown that hot deformation of the spray formed 70Si30Al alloy is achieved by liquid flow due to isostatic pressure and movement of solid particles due to shear force. Deformation condition depends on the nucleation rate and closure rate of the cavities. The flow stress slightly varies when the difference between the nucleation rate and closure rate of the cavities is small; however, it decreases when the nucleation rate of the cavities is greater than the closure rate of the cavities.
文摘The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sections, including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior, and forecast of the shape and temperature distribution of the billet during the spray forming process.
基金Item Sponsored by National Basic Research Program of China(2011CB606303)Constructed Project for Key Laboratory of Beijing of China
文摘Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. 001-10 s^（-1）. A comprehensive constitutive equation was obtained,which could be used to predict the flow stress at different strains. Processing map was developed on the basis of the flow stress data using the principles of dynamic material model. The results showed that the flow curves were in fair agreement with the dynamic recrystallization model. The flow stresses,which were calculated by the comprehensive constitutive equation,agreed well with the test data at low strain rates（ ≤1 s^（-1））. The material constant（ α）,stress exponent（ n） and the hot deformation activation energy（ Q_（HW）） of the new steel were 0. 006 15 MPa^（-1）,4. 81 and 546 kJ·mol^（-1）,respectively. Analysis of the processing map with an observation of microstructures revealed that hot working processes of the steel could be carried out safely in the domain（ T = 1 050-1 150 ℃,ε = 0. 01- 0. 1 s^（-1））with about 33% peak efficiency of power dissipation（ η）. Cracks was expected in two domains at either lower temperatures（ 〈 1 000 ℃） or low strain rates（ 0. 001 s^（-1）） with different cracking mechanisms. Flow localization occurred when the strain rates exceeded 1 s^（-1） at all testing temperatures.
基金Sponsored by National High Technology Research and Development Program(863Program)of China(2007AA03Z502)
文摘The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed grains.The measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are analyzed.Also,effects of heat treatment on microstructure were discussed.The results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the microstructure.Regarding processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.
