In this study,Al-30W(wt.%)alloy powder was prepared by Aluminothermic reduction and hightemperature gas atomization.We then studied the phase composition,surface morphology,spatial phase structure,and thermal oxidatio...In this study,Al-30W(wt.%)alloy powder was prepared by Aluminothermic reduction and hightemperature gas atomization.We then studied the phase composition,surface morphology,spatial phase structure,and thermal oxidation process using XRD,SEM/EDS,TEM,DSC,and DTA/TG analysis.The results showed that the Al-30W alloy powder exhibited high sphericity,and the interior presented a special spatial phase structure in which the Al/W amorphous alloy phase and the metastable Al/W intermetallic compound phase were distributed in the pure Al matrix.When the Al-30W alloy powder was stabilized in a vacuum tube furnace,the spatial phase structure of the alloy powder changed,and a small amount of pure Al was embedded in the Al_(12)W matrix.The resulting Al-30W alloy powder products,treated in air at different temperatures,were collected in situ and characterized.The results presented that with an increase in temperature,the types and morphologies of the Al/W intermetallic compounds in the Al-30W alloy powder changed.Furthermore,the Al-30W alloy powder began to undergo intense oxidation reactions at about 900℃,accompanied by a concentrated energy release and rapid weight gain.The volatilization of WO_(3)produced in the oxidation process promoted the complete oxidation of the Al-30W alloy powder,and the Al-30W alloy powder was completely oxidized at 1300℃.At this stage,all W atoms were transformed into gaseous WO_(3),and only a large number of small Al_(2)O_(3)fragments remained in the oxidation product.Thus,the Al-30W alloy powder exhibited excellent thermal reactivity and oxidation integrity,and may offer excellent application prospects in the field of energetic materials.展开更多
Phase equilibria at Fe-Mn side of isothermal section at 1000 and 1100℃ in Fe-Mn- Al system have been determined using the diffusion couple technique and metallography. A three-phase,α+γ+β,region was found at 1000...Phase equilibria at Fe-Mn side of isothermal section at 1000 and 1100℃ in Fe-Mn- Al system have been determined using the diffusion couple technique and metallography. A three-phase,α+γ+β,region was found at 1000℃.The method of solid/gas diffusion couple used to determine equilibrium phase composition is believed to be feasible for the system containing volatile component.展开更多
The study systematically investigated the effects of master alloy addition containing rare earth elements La and Yb on the microstructures characteristic and tensile properties of A1Sil0Cu3 alloy. It was studied by me...The study systematically investigated the effects of master alloy addition containing rare earth elements La and Yb on the microstructures characteristic and tensile properties of A1Sil0Cu3 alloy. It was studied by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy diffraction spectnam and differential thermal analyzer. The results showed that the ad-dition of （La＋Yb） obviously reduced the sizes of the primary a-Al phase and eutectic Si particles as well as 13-A15FeSi phase and im- proved the morphology of the primary a-A1 phase and eutectic Si particles. The optimum addition of（La＋Yb） addition was 0.6 wt.%. Comparing the 0.6 wt.% （La＋Yb） modified A1Sil0Cu3 alloy with the unmodified alloy, it was found that the mean diameter, mean area and SADS of primary a-A1 phase were decreased by 50.80%, 75.74% and 50.83% respectively; the aspect ratio, size （length） and mean area of eutectic Si particles were decreased by 66.30%, 81.78% and 78.99%, respectively, and the average size of the β-AlsFeSi phase was 16.4 pro. In addition, the addition of （La＋Yb） greatly improved the tensile properties ofA1Si 10Cu3 alloy, especially in the ultimate tensile strength and elongation as a result of the significant improvement in microstructure.展开更多
The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and i...The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and its modification mechanism by Sb and Sr were investigated using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and differential thermal analysis （DTA）. The results indicate that by adding 0.5wt.% Sb to the Mg-12Al-0.7Si alloy, the Mg17Al12 phase was refined and broken into some discontinuous island structures. However, some network Mg17Al12 phases still can be detected in Mg-12Al-0.7Si-0.09Sr alloy. Therefore, Sb performs better in modification and refinement of Mg17Al12 phase than does Sr. Small amounts of fine polygonal shaped Mg2Si phases were found in Mg-12AI-0.7Si-0.5Sb alloy, while the morphology of Mg2Si phases in Mg-12Al-0.7Si-0.09Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg2Si phase are more significant by adding 0.09wt.% Sr than 0.5wt.% Sb. The ultimate tensile strengths of the Sb and Sr modified Mg-12Al-0.7Si alloys were considerably increased both at room temperature and at 200 ℃.展开更多
In the present study,the effects of equal channel angular pressing(ECAP)on the microstructure and mechanical property of the Mg-20Al alloy were systematically investigated.For the first time,the texture of Mg17Al12 ph...In the present study,the effects of equal channel angular pressing(ECAP)on the microstructure and mechanical property of the Mg-20Al alloy were systematically investigated.For the first time,the texture of Mg17Al12 phase and its evolution with ECAP conditions were reported.The results show that increasing the processing temperature and passes generates more uniform distribution and finer size ofβ-Mg17Al12 phases.The large pieces ofβ-Mg17A12 phases are composed of many fine grains with different crystallographic orientations.For theβ-Mg17A12 phase,a preferred distribution of(001)appears at 523 K and 573 K,and hardly varies with temperature.Nevertheless,a random texture is observed at 623 K.The(0002)poles exhibit a preferred distribution at 473 K,but this preferred distribution varies with temperature.A random distribution of(0002)poles is observed when processed at 623 K.Many types of crystallographic planar relationship betweenβ-Mg17A12 phase andα-Mg matrix are observed and the relationships of{11-23}//{100}or{110}or{111}and{1-211}//{100}or//{110}or{111}have a relatively higher frequency than others.The texture ofα-Mg matrix is much different from that of the ECAPed Mg alloys with a relative low Al content,in which a texture with basal poles inclining approximately 45°away from the extrusion direction often develops.The mechanical properties of Mg-20Al alloy are closely related to the temperature and passes of ECAP.A higher temperature often decreases the yield strength,but hardly alters the maximum strength.There is a low plasticity for all the samples and increasing processing temperature slightly enhances the plasticity.The corresponding mechanisms were deeply discussed.展开更多
Solidification curve of Al 8.5Fe 1.7Si was calculated by thermodynamic models. Phase constitutions of Al 8.5Fe, Al 8.5Fe 1.7Si and Al 8.5Fe 1.7Si 1.3V alloys were analysed at different cooling rates by means of optica...Solidification curve of Al 8.5Fe 1.7Si was calculated by thermodynamic models. Phase constitutions of Al 8.5Fe, Al 8.5Fe 1.7Si and Al 8.5Fe 1.7Si 1.3V alloys were analysed at different cooling rates by means of optical microscopy, X ray diffraction, transmission electron microscopy and so on. Microstructures of spraying deposited ingots and their hot processed samples were detected, and the phase transitions during spraying deposition, heating process and hot processing were also studied. The results show that, by spraying deposition, the ideal structures of α (Al) and Al 12 (Fe, V) 3Si can be obtained when cooling rate is above 10 5 K/s; and restraining the formation of Al 8(Fe,V) 2Si/Al 13 Fe 4 can improve the properties of the alloy.展开更多
The dendrite growth process during the solidification of the Al-4.5%Cu binary alloy was simulated using the phase-field model, proposed by Kim et al. Solute diffusion equation and heat transfer equation were solved si...The dendrite growth process during the solidification of the Al-4.5%Cu binary alloy was simulated using the phase-field model, proposed by Kim et al. Solute diffusion equation and heat transfer equation were solved simultaneously. The effects of the noise on the dendrite growth, solute and temperature profile in the undercooled alloy melt were investigated. The results indicate that the noise can trigger the growth of the secondary arms, and increase the highest temperature and solute concentration, but not influence the tip operating state. The solute and temperature gradients in the tip are the highest.展开更多
The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe micr...The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe microanalysis. There coexist three single phase fields, two two phase fields and one three phase field. It is established that the phase Al 3Sc 10.5 Zr 00.5 with L1 2 structure and Al 3Zr 10.8 Sc 00.2 with DO 23 structure are in equilibrium with the α solid solution, Zr being dissolved in Al 3Sc, further substituting for about 50% Sc(mole fraction) whilst Sc is present in the phase Al 3Zr and the maximum substitution for Zr is about 20%.展开更多
The liquid phase behavior of the fine-grained 5083 AI alloy obtained through thermomechanical process was investigated during the tensile tests in a temperature range of 380-570℃ and strain rate range of 4.17× 1...The liquid phase behavior of the fine-grained 5083 AI alloy obtained through thermomechanical process was investigated during the tensile tests in a temperature range of 380-570℃ and strain rate range of 4.17× 10^-4- 1.0× 10^-2 s^-1. The maximum elongation 530% of the fine-grained 5083 AI alloy was obtained at 550℃ and 4.17× 10^-4 s^-1. Fracture analysis by scanning electron microscopy （SEM） indicated that the formation of filament （formed by liquid phase） was greatly affected by the tensile temperature and strain rate. The results also showed that the optimum morphology of formed filament was obtained at 550℃ and a strain rate of 4.17× 10^-4 s^-1. The effect of liquid phase on superplastic deformation of the alloy was further discussed.展开更多
基金supported by the National Natural Science Foundation of China(No.51871106).We express our grat-itude for analyzing and testing of Huazhong University of Science and Technology Analytical&Testing Center.
文摘In this study,Al-30W(wt.%)alloy powder was prepared by Aluminothermic reduction and hightemperature gas atomization.We then studied the phase composition,surface morphology,spatial phase structure,and thermal oxidation process using XRD,SEM/EDS,TEM,DSC,and DTA/TG analysis.The results showed that the Al-30W alloy powder exhibited high sphericity,and the interior presented a special spatial phase structure in which the Al/W amorphous alloy phase and the metastable Al/W intermetallic compound phase were distributed in the pure Al matrix.When the Al-30W alloy powder was stabilized in a vacuum tube furnace,the spatial phase structure of the alloy powder changed,and a small amount of pure Al was embedded in the Al_(12)W matrix.The resulting Al-30W alloy powder products,treated in air at different temperatures,were collected in situ and characterized.The results presented that with an increase in temperature,the types and morphologies of the Al/W intermetallic compounds in the Al-30W alloy powder changed.Furthermore,the Al-30W alloy powder began to undergo intense oxidation reactions at about 900℃,accompanied by a concentrated energy release and rapid weight gain.The volatilization of WO_(3)produced in the oxidation process promoted the complete oxidation of the Al-30W alloy powder,and the Al-30W alloy powder was completely oxidized at 1300℃.At this stage,all W atoms were transformed into gaseous WO_(3),and only a large number of small Al_(2)O_(3)fragments remained in the oxidation product.Thus,the Al-30W alloy powder exhibited excellent thermal reactivity and oxidation integrity,and may offer excellent application prospects in the field of energetic materials.
文摘Phase equilibria at Fe-Mn side of isothermal section at 1000 and 1100℃ in Fe-Mn- Al system have been determined using the diffusion couple technique and metallography. A three-phase,α+γ+β,region was found at 1000℃.The method of solid/gas diffusion couple used to determine equilibrium phase composition is believed to be feasible for the system containing volatile component.
基金supported by the National Natural Science Foundation of China(51364035,51165032)Ministry of Education tied up with the Special Research Fund for the Doctoral Program for Higher School(20133601110001)Loading Program of Science and Technology of College of Jiangxi Province(KJLD14003)
文摘The study systematically investigated the effects of master alloy addition containing rare earth elements La and Yb on the microstructures characteristic and tensile properties of A1Sil0Cu3 alloy. It was studied by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy diffraction spectnam and differential thermal analyzer. The results showed that the ad-dition of （La＋Yb） obviously reduced the sizes of the primary a-Al phase and eutectic Si particles as well as 13-A15FeSi phase and im- proved the morphology of the primary a-A1 phase and eutectic Si particles. The optimum addition of（La＋Yb） addition was 0.6 wt.%. Comparing the 0.6 wt.% （La＋Yb） modified A1Sil0Cu3 alloy with the unmodified alloy, it was found that the mean diameter, mean area and SADS of primary a-A1 phase were decreased by 50.80%, 75.74% and 50.83% respectively; the aspect ratio, size （length） and mean area of eutectic Si particles were decreased by 66.30%, 81.78% and 78.99%, respectively, and the average size of the β-AlsFeSi phase was 16.4 pro. In addition, the addition of （La＋Yb） greatly improved the tensile properties ofA1Si 10Cu3 alloy, especially in the ultimate tensile strength and elongation as a result of the significant improvement in microstructure.
基金financially supported by the National Natural Science Foundation of China(Grant nos.:51301118,51404166)the Projects of International Cooperation in Shanxi province,China(Grant no.:2014081002)and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi province,China(Grant nos.:2013108,2014120)
文摘The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and its modification mechanism by Sb and Sr were investigated using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and differential thermal analysis （DTA）. The results indicate that by adding 0.5wt.% Sb to the Mg-12Al-0.7Si alloy, the Mg17Al12 phase was refined and broken into some discontinuous island structures. However, some network Mg17Al12 phases still can be detected in Mg-12Al-0.7Si-0.09Sr alloy. Therefore, Sb performs better in modification and refinement of Mg17Al12 phase than does Sr. Small amounts of fine polygonal shaped Mg2Si phases were found in Mg-12AI-0.7Si-0.5Sb alloy, while the morphology of Mg2Si phases in Mg-12Al-0.7Si-0.09Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg2Si phase are more significant by adding 0.09wt.% Sr than 0.5wt.% Sb. The ultimate tensile strengths of the Sb and Sr modified Mg-12Al-0.7Si alloys were considerably increased both at room temperature and at 200 ℃.
基金supported by the Natural Science Foundation of China(51871032)Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYB17004)+1 种基金Fundamental Research Funds for the Central Universities(2019CDQYCL032)the“111”Project(B16007)by the Ministry of Education。
文摘In the present study,the effects of equal channel angular pressing(ECAP)on the microstructure and mechanical property of the Mg-20Al alloy were systematically investigated.For the first time,the texture of Mg17Al12 phase and its evolution with ECAP conditions were reported.The results show that increasing the processing temperature and passes generates more uniform distribution and finer size ofβ-Mg17Al12 phases.The large pieces ofβ-Mg17A12 phases are composed of many fine grains with different crystallographic orientations.For theβ-Mg17A12 phase,a preferred distribution of(001)appears at 523 K and 573 K,and hardly varies with temperature.Nevertheless,a random texture is observed at 623 K.The(0002)poles exhibit a preferred distribution at 473 K,but this preferred distribution varies with temperature.A random distribution of(0002)poles is observed when processed at 623 K.Many types of crystallographic planar relationship betweenβ-Mg17A12 phase andα-Mg matrix are observed and the relationships of{11-23}//{100}or{110}or{111}and{1-211}//{100}or//{110}or{111}have a relatively higher frequency than others.The texture ofα-Mg matrix is much different from that of the ECAPed Mg alloys with a relative low Al content,in which a texture with basal poles inclining approximately 45°away from the extrusion direction often develops.The mechanical properties of Mg-20Al alloy are closely related to the temperature and passes of ECAP.A higher temperature often decreases the yield strength,but hardly alters the maximum strength.There is a low plasticity for all the samples and increasing processing temperature slightly enhances the plasticity.The corresponding mechanisms were deeply discussed.
文摘Solidification curve of Al 8.5Fe 1.7Si was calculated by thermodynamic models. Phase constitutions of Al 8.5Fe, Al 8.5Fe 1.7Si and Al 8.5Fe 1.7Si 1.3V alloys were analysed at different cooling rates by means of optical microscopy, X ray diffraction, transmission electron microscopy and so on. Microstructures of spraying deposited ingots and their hot processed samples were detected, and the phase transitions during spraying deposition, heating process and hot processing were also studied. The results show that, by spraying deposition, the ideal structures of α (Al) and Al 12 (Fe, V) 3Si can be obtained when cooling rate is above 10 5 K/s; and restraining the formation of Al 8(Fe,V) 2Si/Al 13 Fe 4 can improve the properties of the alloy.
文摘The dendrite growth process during the solidification of the Al-4.5%Cu binary alloy was simulated using the phase-field model, proposed by Kim et al. Solute diffusion equation and heat transfer equation were solved simultaneously. The effects of the noise on the dendrite growth, solute and temperature profile in the undercooled alloy melt were investigated. The results indicate that the noise can trigger the growth of the secondary arms, and increase the highest temperature and solute concentration, but not influence the tip operating state. The solute and temperature gradients in the tip are the highest.
文摘The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe microanalysis. There coexist three single phase fields, two two phase fields and one three phase field. It is established that the phase Al 3Sc 10.5 Zr 00.5 with L1 2 structure and Al 3Zr 10.8 Sc 00.2 with DO 23 structure are in equilibrium with the α solid solution, Zr being dissolved in Al 3Sc, further substituting for about 50% Sc(mole fraction) whilst Sc is present in the phase Al 3Zr and the maximum substitution for Zr is about 20%.
文摘The liquid phase behavior of the fine-grained 5083 AI alloy obtained through thermomechanical process was investigated during the tensile tests in a temperature range of 380-570℃ and strain rate range of 4.17× 10^-4- 1.0× 10^-2 s^-1. The maximum elongation 530% of the fine-grained 5083 AI alloy was obtained at 550℃ and 4.17× 10^-4 s^-1. Fracture analysis by scanning electron microscopy （SEM） indicated that the formation of filament （formed by liquid phase） was greatly affected by the tensile temperature and strain rate. The results also showed that the optimum morphology of formed filament was obtained at 550℃ and a strain rate of 4.17× 10^-4 s^-1. The effect of liquid phase on superplastic deformation of the alloy was further discussed.
