A new method was exploited using solution treatment and aging process as a pretreatment in preparing semi-solid slurry with fine microstructure before isothermal treatment of wrought aluminum alloy 7A09.Parameters of ...A new method was exploited using solution treatment and aging process as a pretreatment in preparing semi-solid slurry with fine microstructure before isothermal treatment of wrought aluminum alloy 7A09.Parameters of pretreatment were optimized by orthogonal experiment design and proper precursor was prepared.The evolution of microstructure of semi-solid slurry during isothermal treatment was analyzed and the mechanism of microstructure refining was discussed.The result of orthogonal experiment design shows that the optimum parameters are 462 ℃for solution temperature,40min for solution time,132 ℃for aging temperature and 14 h for aging time.Microstructure of isothermal treatment is fine,homogenous,with globular solid grains and a solid fraction between 50%and 70%,which is qualified for later semi-solid forming process.Mechanism of microstructure evolution includes the agglomeration ofα-phase and Ostwald ripening.Precipitations prepared by solution and aging treatment prevent the grains from coarsening and promote the grain ripening to globular shape.展开更多
The effects of solution heat treatment on the microstructure and mechanical properties of AZ61-0.7Si magnesium alloy were investigated.The results indicate that the solution heat treatment can modify the Chinese scrip...The effects of solution heat treatment on the microstructure and mechanical properties of AZ61-0.7Si magnesium alloy were investigated.The results indicate that the solution heat treatment can modify the Chinese script shaped Mg2Si phases in the AZ61-0.7Si magnesium alloy.After being solutionized at 420℃ for 16-48 h,the morphology of the Mg2Si phases in the AZ61-0.7Si alloy changes from the Chinese script shape to the short pole and block shapes.Accordingly,the tensile and creep properties of the AZ61-0.7Si alloy are improved.After being solutionized at 420℃ for 24 h and followed by aging treatment at 200℃ for 12 h,the heat-treated alloy exhibits relatively high tensile and creep properties than those of the as-cast alloy.展开更多
The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25...The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25Mn)casting magnesium alloy were investigated and compared.The results indicate that the microstructures of all the aged alloys under the three treatment processes are mainly composed ofα-Mg,Mg17Al12),and Al4Mn phases,indicating that the double-stage and reverse double-stage aging treatments have no obvious effect on the type of alloy phases.However,as compared with the single-stage and double-stage processes,the reverse double-stage process has a great effect on the quantity of the Mg17Al12phases.After the reverse double-stage aging treatment,which results in a stronger drive for decomposition of the supersaturated solid solution,the number of Mg17Al12phases precipitated in the grains significantly increases.In addition,as compared with the single-stage aged alloy,the tensile properties at room temperature for both the double-stage and reverse double-stage aged alloys are significantly improved.Among them,the reverse double-stage aged alloy achieves the highest tensile strength,yield strength,and elongation of 295 MPa,167 MPa,and 8.6%,respectively.展开更多
The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases...The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases and polynary eutectic phases with low melting point formwith increase of Cu content. Gradual solution treatment includes two steps: solution treating nearthe melting point of polynary eutectic phase to take it dissolve first, and then increasing solutiontemperature to take the remainder copper intermetallics dissolved into alpha (Al). Grain boundariesmelting can be avoided by gradual solution treatment, even the maximum solution temperature isabove final solidification point, and the age hardening response increases correspondingly展开更多
Aluminum alloys are used as substitutes for fiber reinforced polymer(FRP) in ships and boats.However,ships constructed with 5000-series Al alloy suffer a little corrosion in the marine environment,when they run in hig...Aluminum alloys are used as substitutes for fiber reinforced polymer(FRP) in ships and boats.However,ships constructed with 5000-series Al alloy suffer a little corrosion in the marine environment,when they run in high speed,and high flow rate,etc.Therefore,solution heat treatment was carried out to prevent corrosion.The optimal heat treatment involved heating specimens for 120 min at 420 ℃ and then cooling them in water.In addition,the optimal ageing condition involved ageing specimens for 240 min at 180 ℃.The slow strain rate test(SSRT) in a seawater revealed that heat treatment under optimal conditions produced improved elongation,time-to-fracture and amount of dimples compared with the as-received specimen.展开更多
Mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after solution treatments were investigated by means of optical microscopy (OM), tensile test, hardness measurement and electrical conductivity test, d...Mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after solution treatments were investigated by means of optical microscopy (OM), tensile test, hardness measurement and electrical conductivity test, differential scanning calorimetric (DSC), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transition electron microscopy (TEM), respectively. The results show that both tensile strength and hardness increase first and then decrease with temperature at constant holding time of 30 min with maximum strength and hardness appearing at 520 ℃. Tensile strength, hardness and elongation of samples treated at 520 ℃ for 30 min are 566 MPa (σb ), 512 MPa (σ0.2 ), HB 148 and 8.23% (δ), respectively. There are certain amount of fine T1 (Al2 CuLi) phase dispersing among Al substrates according to TEM images. This may result in mixed fracture morphology with trans-granular and inter-granular delamination cracks observed in SEM images.展开更多
The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron pr...The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and energy dispersive spectroscopy(EDS).The solidus and liquidus of single crystal alloy were obtained by differential scanning calorimetry(DSC).Results show that the mosaic-like eutectic and fan-like eutectic are dissolved at first,and the coarseγ'phase is dissolved later during the solution heat treatment of 1,390°C/2 h+1,310°C/4 h+1,320°C/10 h+air cooling(AC).The composition segregations of Al,Ta,W and Re are 0.99,0.96,1.04 and 1.16,respectively,which close to 1.The incipient melting is caused by the low local temperature of the alloy,and the micropore region with a lower melting point is the preferred position for incipient melting.展开更多
In present paper, the effect of enhanced solution on mechanical properties and aging behavior in a commercially available 2024A1 alloy were investigated using tension test and scanning electron microscopy. Differentia...In present paper, the effect of enhanced solution on mechanical properties and aging behavior in a commercially available 2024A1 alloy were investigated using tension test and scanning electron microscopy. Differential scanning calorimeter (DSC) was used to measure the incipient melting behavior and then determine the technology parameter of enhanced solution heat treatment for high strength. The results show that an appropriately enhanced solution treatment can make final solution temperature higher than that of the conventional solution temperature and improves second phase solution without the formation of overheated microstructure. As the results, both the strength especially the yield strength and the resistance to over aging can be improved considerably without a large deterioration to tensile ductility.展开更多
The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodif...The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si,Cu_3NiAl_6 and Mg_2Si phases in theα-Al matrix but different in size and morphology.Both size and inter-particle spacing of Si particles were significantly changed by increasing the solution treatment time.After a short solution treatment,the coarse acicular plate of the eutectic Si appears to be fragmented.Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time compared to unmodified alloy.The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys.Compared to 10 h solution treatment,the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.展开更多
Directed energy deposition-arc(DED-Arc)technology has the advantages of simple equipment,low manufacturing cost and high deposition rate,while the use of DED-Arc has problems of microstructure inhomogeneity,position d...Directed energy deposition-arc(DED-Arc)technology has the advantages of simple equipment,low manufacturing cost and high deposition rate,while the use of DED-Arc has problems of microstructure inhomogeneity,position dependence of macroscopic mechanical properties and anisotropy.Therefore,it is necessary to carry out a subsequent heat treatment to improve its microstructure uniformity,mechanical properties and superelasticity.In this investigation,the DED-Arc 15-layer NiTi alloy thin-walled parts with the solution treatment at different process parameters were studied to analyze the effects of solution heat treatment on microstructure,phase composition,phase transformation,microhardness,tensile and superelasticity.The temperature range of solution treatment is 800-1050℃,and the treatment time range is 1-5.5 h.The results show that after solution treatment at 800℃/1 h,the content of precipitated phase decreases,the grain is refined,the microhardness increases,and the mechanical properties in the 0°direction are improved.The strain recovery rate after 10 tensile cycles has increased from 37.13%(as-built)to 49.25%(solid solution treatment).This research provides an effective post treatment method for high-performance DED-Arc NiTi shape memory alloys.展开更多
The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for ...The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for solution treatment and aging treatment. Experimental results show that the dendritic arms are broken and a large quantity of equiaxed grains appear in the microstructure of specimens with electromagnetic stirring(EMS).With the increase of the quenching temperature(150-350℃),the solution of Mg and Al in solidβphase increases,and the Brinell hardness of the alloy increases as well.Aging peak and over aging happen becauseθ(MgLi_2Al) which precipitates in theβmatrix and strengthens the alloy is unstable and transforms to stable AlLi phase.Aging curves of EMS specimens change in a smaller amplitude.展开更多
The research is carried out through specification measurement of magnetic property, photo analysis of electronic microscope, metallographic analysis, micro hard and so on means. The initial researches have been d...The research is carried out through specification measurement of magnetic property, photo analysis of electronic microscope, metallographic analysis, micro hard and so on means. The initial researches have been done about the influence on material property by solid solution treatment, heat magnetic treatment and aging treatment technology of the low cobalt Fe Cr Co alloy. Therefore, better productive technologies have been found.展开更多
Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue...Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.展开更多
The effects of deformation and heat-treatment on texture of BSCCO-2223/Ag tapes were investigatedby using single orientation quantitative texture analytical methods. The results show that when tapes weresintered at 83...The effects of deformation and heat-treatment on texture of BSCCO-2223/Ag tapes were investigatedby using single orientation quantitative texture analytical methods. The results show that when tapes weresintered at 835℃ for 24~48 h, the texture developed quickly, and further prolonging sintering tirne hadno significant influence on it. With the increase of deformation rate, the volume fraction of c-axis texturewas improved in linear form at first and then changed slowly. The highest volume fraction of c-axis texture(vol%)in these experiments is 33 . 49 % .展开更多
Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after soln...Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after solntionized at 525 ℃ for 12 h. The evolution of the phase constituents from as-cast to cast-T4 was as follows: α-Mg solid solution+Mg5(Gd,Y) entectic compound→α-Mg solid solution+ spheroidized Mg5(Gd, Y) phase→α-Mg supersaturated solid solution+cuboid-shaped compound (Mg2Y3Gd2). And the precipitation sequences of Mg-15Gd-5Y-0.5Zr alloy were observed, according to the hardness response to isothermal ageing at 225-300 ℃ for 0-128 h.展开更多
The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and stren...The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and strength of samples of nine groups under duplex aging conditions and three retrogression and reaging heat treatments were also measured. Incorporating the microstructure and property, we found that when the condition of the first order aging kept identical, the fracture toughness and stress corrosion cracking resistance increase with aging time and the second aging temperature. The optimal treatment conditions are ( 115℃×7h + 185 ℃×13h) among all tested two-stage aging treatments. Although the 7475 alloy treated by RRA method shows the highest strength and its stress corrosion cracking resistance after twenty minutes retrogression can also reach the same level as those by the optimal treatment of (115℃×7h+ 185℃×13h ), the fracture toughness is even low.展开更多
基金Project(2007-83)supported by Science and Technology Development Projects of Weihai,Shandong Province。
文摘A new method was exploited using solution treatment and aging process as a pretreatment in preparing semi-solid slurry with fine microstructure before isothermal treatment of wrought aluminum alloy 7A09.Parameters of pretreatment were optimized by orthogonal experiment design and proper precursor was prepared.The evolution of microstructure of semi-solid slurry during isothermal treatment was analyzed and the mechanism of microstructure refining was discussed.The result of orthogonal experiment design shows that the optimum parameters are 462 ℃for solution temperature,40min for solution time,132 ℃for aging temperature and 14 h for aging time.Microstructure of isothermal treatment is fine,homogenous,with globular solid grains and a solid fraction between 50%and 70%,which is qualified for later semi-solid forming process.Mechanism of microstructure evolution includes the agglomeration ofα-phase and Ostwald ripening.Precipitations prepared by solution and aging treatment prevent the grains from coarsening and promote the grain ripening to globular shape.
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2007CB613704)supported by the National Basic Research Program of ChinaProject(2006AA4012-9-6,2007BB4400)supported by the Chongqing Science and Technology Commission,China
文摘The effects of solution heat treatment on the microstructure and mechanical properties of AZ61-0.7Si magnesium alloy were investigated.The results indicate that the solution heat treatment can modify the Chinese script shaped Mg2Si phases in the AZ61-0.7Si magnesium alloy.After being solutionized at 420℃ for 16-48 h,the morphology of the Mg2Si phases in the AZ61-0.7Si alloy changes from the Chinese script shape to the short pole and block shapes.Accordingly,the tensile and creep properties of the AZ61-0.7Si alloy are improved.After being solutionized at 420℃ for 24 h and followed by aging treatment at 200℃ for 12 h,the heat-treated alloy exhibits relatively high tensile and creep properties than those of the as-cast alloy.
基金supported by the National Key R&D Program of China(Grant No.2018YFB1106800)the National Natural Science Foundation of China(Grant No.51771152)。
文摘The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25Mn)casting magnesium alloy were investigated and compared.The results indicate that the microstructures of all the aged alloys under the three treatment processes are mainly composed ofα-Mg,Mg17Al12),and Al4Mn phases,indicating that the double-stage and reverse double-stage aging treatments have no obvious effect on the type of alloy phases.However,as compared with the single-stage and double-stage processes,the reverse double-stage process has a great effect on the quantity of the Mg17Al12phases.After the reverse double-stage aging treatment,which results in a stronger drive for decomposition of the supersaturated solid solution,the number of Mg17Al12phases precipitated in the grains significantly increases.In addition,as compared with the single-stage aged alloy,the tensile properties at room temperature for both the double-stage and reverse double-stage aged alloys are significantly improved.Among them,the reverse double-stage aged alloy achieves the highest tensile strength,yield strength,and elongation of 295 MPa,167 MPa,and 8.6%,respectively.
基金This work is financially supported by the National Natural Science Foundation of China(No.50071028)the Shandong Natural Science Foundation of China (No.Z2001F02)
文摘The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases and polynary eutectic phases with low melting point formwith increase of Cu content. Gradual solution treatment includes two steps: solution treating nearthe melting point of polynary eutectic phase to take it dissolve first, and then increasing solutiontemperature to take the remainder copper intermetallics dissolved into alpha (Al). Grain boundariesmelting can be avoided by gradual solution treatment, even the maximum solution temperature isabove final solidification point, and the age hardening response increases correspondingly
文摘Aluminum alloys are used as substitutes for fiber reinforced polymer(FRP) in ships and boats.However,ships constructed with 5000-series Al alloy suffer a little corrosion in the marine environment,when they run in high speed,and high flow rate,etc.Therefore,solution heat treatment was carried out to prevent corrosion.The optimal heat treatment involved heating specimens for 120 min at 420 ℃ and then cooling them in water.In addition,the optimal ageing condition involved ageing specimens for 240 min at 180 ℃.The slow strain rate test(SSRT) in a seawater revealed that heat treatment under optimal conditions produced improved elongation,time-to-fracture and amount of dimples compared with the as-received specimen.
基金Foundation item: Project(6140506) supported by GAD (General Armament Department), China
文摘Mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after solution treatments were investigated by means of optical microscopy (OM), tensile test, hardness measurement and electrical conductivity test, differential scanning calorimetric (DSC), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transition electron microscopy (TEM), respectively. The results show that both tensile strength and hardness increase first and then decrease with temperature at constant holding time of 30 min with maximum strength and hardness appearing at 520 ℃. Tensile strength, hardness and elongation of samples treated at 520 ℃ for 30 min are 566 MPa (σb ), 512 MPa (σ0.2 ), HB 148 and 8.23% (δ), respectively. There are certain amount of fine T1 (Al2 CuLi) phase dispersing among Al substrates according to TEM images. This may result in mixed fracture morphology with trans-granular and inter-granular delamination cracks observed in SEM images.
基金The authors would like to express their sincere thanks to the financial support from the Key Project of National Natural Science Foundation of China(No.U16642548).
文摘The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and energy dispersive spectroscopy(EDS).The solidus and liquidus of single crystal alloy were obtained by differential scanning calorimetry(DSC).Results show that the mosaic-like eutectic and fan-like eutectic are dissolved at first,and the coarseγ'phase is dissolved later during the solution heat treatment of 1,390°C/2 h+1,310°C/4 h+1,320°C/10 h+air cooling(AC).The composition segregations of Al,Ta,W and Re are 0.99,0.96,1.04 and 1.16,respectively,which close to 1.The incipient melting is caused by the low local temperature of the alloy,and the micropore region with a lower melting point is the preferred position for incipient melting.
文摘In present paper, the effect of enhanced solution on mechanical properties and aging behavior in a commercially available 2024A1 alloy were investigated using tension test and scanning electron microscopy. Differential scanning calorimeter (DSC) was used to measure the incipient melting behavior and then determine the technology parameter of enhanced solution heat treatment for high strength. The results show that an appropriately enhanced solution treatment can make final solution temperature higher than that of the conventional solution temperature and improves second phase solution without the formation of overheated microstructure. As the results, both the strength especially the yield strength and the resistance to over aging can be improved considerably without a large deterioration to tensile ductility.
文摘The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si,Cu_3NiAl_6 and Mg_2Si phases in theα-Al matrix but different in size and morphology.Both size and inter-particle spacing of Si particles were significantly changed by increasing the solution treatment time.After a short solution treatment,the coarse acicular plate of the eutectic Si appears to be fragmented.Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time compared to unmodified alloy.The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys.Compared to 10 h solution treatment,the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.
基金The study was supported by the National Natural Science Foundation of China(No.52105396).The authors thank the State Key Laboratory of Materials Processing and Die&Mould Technology,and the Analytical&Testing Center,Huazhong University of Science&Technology for the extensive experiments.
文摘Directed energy deposition-arc(DED-Arc)technology has the advantages of simple equipment,low manufacturing cost and high deposition rate,while the use of DED-Arc has problems of microstructure inhomogeneity,position dependence of macroscopic mechanical properties and anisotropy.Therefore,it is necessary to carry out a subsequent heat treatment to improve its microstructure uniformity,mechanical properties and superelasticity.In this investigation,the DED-Arc 15-layer NiTi alloy thin-walled parts with the solution treatment at different process parameters were studied to analyze the effects of solution heat treatment on microstructure,phase composition,phase transformation,microhardness,tensile and superelasticity.The temperature range of solution treatment is 800-1050℃,and the treatment time range is 1-5.5 h.The results show that after solution treatment at 800℃/1 h,the content of precipitated phase decreases,the grain is refined,the microhardness increases,and the mechanical properties in the 0°direction are improved.The strain recovery rate after 10 tensile cycles has increased from 37.13%(as-built)to 49.25%(solid solution treatment).This research provides an effective post treatment method for high-performance DED-Arc NiTi shape memory alloys.
基金Project(107031)supported by the Key Grant of Science & Technology of the Ministry of Education of China
文摘The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for solution treatment and aging treatment. Experimental results show that the dendritic arms are broken and a large quantity of equiaxed grains appear in the microstructure of specimens with electromagnetic stirring(EMS).With the increase of the quenching temperature(150-350℃),the solution of Mg and Al in solidβphase increases,and the Brinell hardness of the alloy increases as well.Aging peak and over aging happen becauseθ(MgLi_2Al) which precipitates in theβmatrix and strengthens the alloy is unstable and transforms to stable AlLi phase.Aging curves of EMS specimens change in a smaller amplitude.
文摘The research is carried out through specification measurement of magnetic property, photo analysis of electronic microscope, metallographic analysis, micro hard and so on means. The initial researches have been done about the influence on material property by solid solution treatment, heat magnetic treatment and aging treatment technology of the low cobalt Fe Cr Co alloy. Therefore, better productive technologies have been found.
文摘Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.
文摘The effects of deformation and heat-treatment on texture of BSCCO-2223/Ag tapes were investigatedby using single orientation quantitative texture analytical methods. The results show that when tapes weresintered at 835℃ for 24~48 h, the texture developed quickly, and further prolonging sintering tirne hadno significant influence on it. With the increase of deformation rate, the volume fraction of c-axis texturewas improved in linear form at first and then changed slowly. The highest volume fraction of c-axis texture(vol%)in these experiments is 33 . 49 % .
基金the Major State Basic Research Development Program of China (973 Program, 5133001E)
文摘Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after solntionized at 525 ℃ for 12 h. The evolution of the phase constituents from as-cast to cast-T4 was as follows: α-Mg solid solution+Mg5(Gd,Y) entectic compound→α-Mg solid solution+ spheroidized Mg5(Gd, Y) phase→α-Mg supersaturated solid solution+cuboid-shaped compound (Mg2Y3Gd2). And the precipitation sequences of Mg-15Gd-5Y-0.5Zr alloy were observed, according to the hardness response to isothermal ageing at 225-300 ℃ for 0-128 h.
文摘The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and strength of samples of nine groups under duplex aging conditions and three retrogression and reaging heat treatments were also measured. Incorporating the microstructure and property, we found that when the condition of the first order aging kept identical, the fracture toughness and stress corrosion cracking resistance increase with aging time and the second aging temperature. The optimal treatment conditions are ( 115℃×7h + 185 ℃×13h) among all tested two-stage aging treatments. Although the 7475 alloy treated by RRA method shows the highest strength and its stress corrosion cracking resistance after twenty minutes retrogression can also reach the same level as those by the optimal treatment of (115℃×7h+ 185℃×13h ), the fracture toughness is even low.