The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging （500℃ for 15 rain）, the hardness and the conductivity of the alloy rap...The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging （500℃ for 15 rain）, the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.展开更多
A rapidly solidified Al-2.5Ti-2.5Fe-2.5Cr (mass fraction in percent) alloywas prepared by melt spinning. As-quenched and as-annealed microstructures were studied by X-raydiffractometry (XRD), transmission electron mic...A rapidly solidified Al-2.5Ti-2.5Fe-2.5Cr (mass fraction in percent) alloywas prepared by melt spinning. As-quenched and as-annealed microstructures were studied by X-raydiffractometry (XRD), transmission electron microscopy (TEM), high-resolution transmission electronmicroscopy (HREM) and energy dispersive spectrum (EDS) analysis. The microhardness of the alloy atdifferent annealing temperatures was measured. The results obtained indicate that the microhardnessof the rapidly solidified Al-2.5Ti-2.5Fe-2.5Cr alloy does not vary with different annealingtemperatures. The as-quenched microstructure of the alloy includes two kinds of dispersed primaryphases: Al_3Ti and Al_(13)(Cr, Fe)_2. After annealing at 400 deg C for 10 h, the stable phaseAl_(13)Fe_4 appears in the microstructure.展开更多
Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-S...Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.展开更多
Rapidly solidified Al92.3Fe4.3V0.7Si1.7Mm1.0 alloy has been studied by positron lifetime spectroscopy and the variations on the intedecial defects with the annealing temperature were revealed by an analysis of the lif...Rapidly solidified Al92.3Fe4.3V0.7Si1.7Mm1.0 alloy has been studied by positron lifetime spectroscopy and the variations on the intedecial defects with the annealing temperature were revealed by an analysis of the lifetime results. The intedece characteristics derived from the positron-lifetime results could be used to give a satisfactory interpretation of the dependence of mechanical properties on the annealing temperature展开更多
The paper investigated the effects of RE on the microstructure and ductility of melt-spun Al-63.3at.%Ni and Al-66.4at%Ni.For Al-63.3at.%Ni without RE the microstructure is a mixture of equiaxed martensitic grains and ...The paper investigated the effects of RE on the microstructure and ductility of melt-spun Al-63.3at.%Ni and Al-66.4at%Ni.For Al-63.3at.%Ni without RE the microstructure is a mixture of equiaxed martensitic grains and B2 NiAl grains,but after addition of 0.2wt% RE a complete supersaturated B2 NiAl results,and its elongation is enhanced from 0.9%(without RE) to 1.4%(with 0.2wt%RE).For Al-66.4at.%Ni without RE the microstructure is coarse equiaxed martensitic grains with Ni3Al precipitated at the GBs.But complete martensitic grains and supersaturated single phase,B2 NiAl,would result with addition of 0.05wt%RE and 0.2-0.8wt%RE respectively.The elongation of Al-66.4at.%Ni without RE is only 0.8%.With the addition of 0.05, 0.2 and 0.8wt%RE.the elongation can reach 2.6,3.0 and 3.2% respectively.The addition of RE can change the fracture mode from intergranular fracture(without RE) to a mixture of intergranular and transgranular fracture or entirely transgranular fracture.The mechanisms of microstructure formation and ductility enhancement are analyzed.展开更多
Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prep...Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prepared bulk microcrystalline T15 high speed steel materials by hot extruding or HIPing and hot rolling of the powders,observed and measured the microstructure and performance of the bulk materials.It was shown that rapid solidification may change the solidification characteristics and structure of T15 high speed steel powder and improve the qualities and properties of T15 high speed steel materials.展开更多
Rapidly solidified aging is an effective way to refine the microstructure of Cu-Cr-Sn-Zn lead frame alloy and enhance its hardness. The artificial neural network methodology(ANN) along with genetic algorithms were use...Rapidly solidified aging is an effective way to refine the microstructure of Cu-Cr-Sn-Zn lead frame alloy and enhance its hardness. The artificial neural network methodology(ANN) along with genetic algorithms were used for data analysis and optimization. In this paper the input parameters of the artificial neural network (ANN) are the aging temperature and aging time. The outputs of the ANN model are the hardness and conductivity properties. Some explanations of these predicted results from the microstructure and precipitation-hardening viewpoint are given. After the ANN model is trained successfully, genetic algorithms(GAs) are applied for optimizing the aging processes parameters.展开更多
Two eutectic alloys Bi-Ag and Bi-Zn were rapidly solidified using melt-spinning technique. X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), and temperature dependence of resistivity (TDR) wer...Two eutectic alloys Bi-Ag and Bi-Zn were rapidly solidified using melt-spinning technique. X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), and temperature dependence of resistivity (TDR) were performed. The solid solubility of both Ag and Zn was extended to the eutectic concentration due to rapid solidification by melt spinning technique and both alloys are single-phase solid solutions. The addition of Ag extended the unit cell in both a and c directions keeping the axial ratio c/a without change, and in case of Zn addition, the unit cell was increased in a direction and decreased in c direction leading to the decrease in the axial ratio c/a. The Bi-Ag eutectic alloy exhibited a semiconducting behavior with energy gap of 280 meV, while Bi-Zn eutectic alloy exhibited metallic behavior.展开更多
FeSi_2 based thermoelectric materials have heen prepared by melt spinning andvacuum hot pressing. Most of the rapidly solidified (melt spinning) powders are thin flakes with athickness less than 0.1 mm. Scanning elect...FeSi_2 based thermoelectric materials have heen prepared by melt spinning andvacuum hot pressing. Most of the rapidly solidified (melt spinning) powders are thin flakes with athickness less than 0.1 mm. Scanning electron microscope (SEM) surface profiles show there arefurther finer grain structures with the characteristic size of about 100 nm in a flake. The samplesobtained by hot uniaxial pressing (HUP) in vacuum have densities higher than 90% the theoreticaldensity of the materials. It was found by SEM observations that the microstructures are verydifferent for vertical and parallel sections of the HUP samples. X-ray diffraction (XRD) analysesshow there are some texture features in the samples. It is considered that the textures of thesamples are originated from the orientation of the flakes that tended to align perpendicular to thehot press axis. WSi_2 was introduced into the powders unexpectedly during melting process before therapid solidification, but it makes the microstructures more easily to be explained.展开更多
As coal and gas outburst is one of the most serious mine disasters, it is very important to at least control it if not prevent it from occurring. Injecting cement slurry or grouting into the coal seam can strengthen t...As coal and gas outburst is one of the most serious mine disasters, it is very important to at least control it if not prevent it from occurring. Injecting cement slurry or grouting into the coal seam can strengthen the seam, increase its rigidity coefficient(f), and reduce the volumetric expansion due to gas energy release.This paper reports the results of laboratory experiments on cement-based high water content slurry having different water-cement ratios(W/C) to be used for coal injection. The results show that as the W/C increases, the mobility of the slurry and its setting time increase. The compressive strength and rupture strength, however, are reduced. Furthermore, high W/C grout shows early strength after 7 days, which can be 80% of its 14-day compressive strength. To achieve rapid setting and early strength, the addition of Na_2SiO_3has proven to give the best result, when the concentration of the additive is 3%. The initial and final setting times are 13 and 21 min shorter than samples without Na_2SiO_3, while the compressive strength is more than double. As a retarder, the initial setting time can be extended to 83 min when tartaric acid of 0.4% concentration is added. Through the orthogonal experiment, the optimum recipe of the new high water content slurry has been determined to be: W/C = 2, tartaric acid = 0.2%, Na_2SiO_3= 3%, and12% bentonite. Reinforcement by injection simulation experiments show that the grouting radius of the new slurry mix is 250 mm when the applied grouting pressure is 60 k Pa, 7-day rupture strength and compressive strength are 5.2 and 6.4 MPa, respectively, and are 37% and 88% higher than ordinary cement grout. It can be concluded that the newly developed slurry mix is more effective than the ordinary mix for reinforcing coal and controlling gas outburst.展开更多
Time dependent nucleation theory was applied to calculate the incubation time required for α Al nucleation in rapid solidified (RS) Al Fe V Si Nd alloys. The nucleation rates were calculated as a function of tem...Time dependent nucleation theory was applied to calculate the incubation time required for α Al nucleation in rapid solidified (RS) Al Fe V Si Nd alloys. The nucleation rates were calculated as a function of temperature, and the critical cooling rates required for the formation of amorphous α Al at different neodymium concentrations were calculated too. The addition of neodymium increases the amorphizablity of α Al by increasing the incubation time and decreasing the nucleation rate and the critical cooling rate. The calculations are fitted to experimental results when liquidus temperatures are estimated from an approximation, which treats Al Fe V Si Nd as quasi binary Al Fe system.展开更多
基金This work was supported by the National“863”High Pro-gram of China(No.2002AA331112)the Doctorate Foun-dation of Northwestern Polytechnical University(CX200409)the Science Research Foundation of Henan University of Science and Technology(No.2004ZY039).
文摘The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging （500℃ for 15 rain）, the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.
文摘A rapidly solidified Al-2.5Ti-2.5Fe-2.5Cr (mass fraction in percent) alloywas prepared by melt spinning. As-quenched and as-annealed microstructures were studied by X-raydiffractometry (XRD), transmission electron microscopy (TEM), high-resolution transmission electronmicroscopy (HREM) and energy dispersive spectrum (EDS) analysis. The microhardness of the alloy atdifferent annealing temperatures was measured. The results obtained indicate that the microhardnessof the rapidly solidified Al-2.5Ti-2.5Fe-2.5Cr alloy does not vary with different annealingtemperatures. The as-quenched microstructure of the alloy includes two kinds of dispersed primaryphases: Al_3Ti and Al_(13)(Cr, Fe)_2. After annealing at 400 deg C for 10 h, the stable phaseAl_(13)Fe_4 appears in the microstructure.
文摘Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.
文摘Rapidly solidified Al92.3Fe4.3V0.7Si1.7Mm1.0 alloy has been studied by positron lifetime spectroscopy and the variations on the intedecial defects with the annealing temperature were revealed by an analysis of the lifetime results. The intedece characteristics derived from the positron-lifetime results could be used to give a satisfactory interpretation of the dependence of mechanical properties on the annealing temperature
文摘The paper investigated the effects of RE on the microstructure and ductility of melt-spun Al-63.3at.%Ni and Al-66.4at%Ni.For Al-63.3at.%Ni without RE the microstructure is a mixture of equiaxed martensitic grains and B2 NiAl grains,but after addition of 0.2wt% RE a complete supersaturated B2 NiAl results,and its elongation is enhanced from 0.9%(without RE) to 1.4%(with 0.2wt%RE).For Al-66.4at.%Ni without RE the microstructure is coarse equiaxed martensitic grains with Ni3Al precipitated at the GBs.But complete martensitic grains and supersaturated single phase,B2 NiAl,would result with addition of 0.05wt%RE and 0.2-0.8wt%RE respectively.The elongation of Al-66.4at.%Ni without RE is only 0.8%.With the addition of 0.05, 0.2 and 0.8wt%RE.the elongation can reach 2.6,3.0 and 3.2% respectively.The addition of RE can change the fracture mode from intergranular fracture(without RE) to a mixture of intergranular and transgranular fracture or entirely transgranular fracture.The mechanisms of microstructure formation and ductility enhancement are analyzed.
文摘Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prepared bulk microcrystalline T15 high speed steel materials by hot extruding or HIPing and hot rolling of the powders,observed and measured the microstructure and performance of the bulk materials.It was shown that rapid solidification may change the solidification characteristics and structure of T15 high speed steel powder and improve the qualities and properties of T15 high speed steel materials.
文摘Rapidly solidified aging is an effective way to refine the microstructure of Cu-Cr-Sn-Zn lead frame alloy and enhance its hardness. The artificial neural network methodology(ANN) along with genetic algorithms were used for data analysis and optimization. In this paper the input parameters of the artificial neural network (ANN) are the aging temperature and aging time. The outputs of the ANN model are the hardness and conductivity properties. Some explanations of these predicted results from the microstructure and precipitation-hardening viewpoint are given. After the ANN model is trained successfully, genetic algorithms(GAs) are applied for optimizing the aging processes parameters.
文摘Two eutectic alloys Bi-Ag and Bi-Zn were rapidly solidified using melt-spinning technique. X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), and temperature dependence of resistivity (TDR) were performed. The solid solubility of both Ag and Zn was extended to the eutectic concentration due to rapid solidification by melt spinning technique and both alloys are single-phase solid solutions. The addition of Ag extended the unit cell in both a and c directions keeping the axial ratio c/a without change, and in case of Zn addition, the unit cell was increased in a direction and decreased in c direction leading to the decrease in the axial ratio c/a. The Bi-Ag eutectic alloy exhibited a semiconducting behavior with energy gap of 280 meV, while Bi-Zn eutectic alloy exhibited metallic behavior.
基金This work was financially supported by the National Natural Science Foundation of China (NSFC 59971044) the International Bureau of the BMBF of Germany (CHN 01/361).
文摘FeSi_2 based thermoelectric materials have heen prepared by melt spinning andvacuum hot pressing. Most of the rapidly solidified (melt spinning) powders are thin flakes with athickness less than 0.1 mm. Scanning electron microscope (SEM) surface profiles show there arefurther finer grain structures with the characteristic size of about 100 nm in a flake. The samplesobtained by hot uniaxial pressing (HUP) in vacuum have densities higher than 90% the theoreticaldensity of the materials. It was found by SEM observations that the microstructures are verydifferent for vertical and parallel sections of the HUP samples. X-ray diffraction (XRD) analysesshow there are some texture features in the samples. It is considered that the textures of thesamples are originated from the orientation of the flakes that tended to align perpendicular to thehot press axis. WSi_2 was introduced into the powders unexpectedly during melting process before therapid solidification, but it makes the microstructures more easily to be explained.
基金financial support of the National Natural Science Foundation of China (No. 51474017)the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China (No. 2014211B013)
文摘As coal and gas outburst is one of the most serious mine disasters, it is very important to at least control it if not prevent it from occurring. Injecting cement slurry or grouting into the coal seam can strengthen the seam, increase its rigidity coefficient(f), and reduce the volumetric expansion due to gas energy release.This paper reports the results of laboratory experiments on cement-based high water content slurry having different water-cement ratios(W/C) to be used for coal injection. The results show that as the W/C increases, the mobility of the slurry and its setting time increase. The compressive strength and rupture strength, however, are reduced. Furthermore, high W/C grout shows early strength after 7 days, which can be 80% of its 14-day compressive strength. To achieve rapid setting and early strength, the addition of Na_2SiO_3has proven to give the best result, when the concentration of the additive is 3%. The initial and final setting times are 13 and 21 min shorter than samples without Na_2SiO_3, while the compressive strength is more than double. As a retarder, the initial setting time can be extended to 83 min when tartaric acid of 0.4% concentration is added. Through the orthogonal experiment, the optimum recipe of the new high water content slurry has been determined to be: W/C = 2, tartaric acid = 0.2%, Na_2SiO_3= 3%, and12% bentonite. Reinforcement by injection simulation experiments show that the grouting radius of the new slurry mix is 250 mm when the applied grouting pressure is 60 k Pa, 7-day rupture strength and compressive strength are 5.2 and 6.4 MPa, respectively, and are 37% and 88% higher than ordinary cement grout. It can be concluded that the newly developed slurry mix is more effective than the ordinary mix for reinforcing coal and controlling gas outburst.
基金Project supported by the National Natural Science Foundation of China(55791020)
文摘Time dependent nucleation theory was applied to calculate the incubation time required for α Al nucleation in rapid solidified (RS) Al Fe V Si Nd alloys. The nucleation rates were calculated as a function of temperature, and the critical cooling rates required for the formation of amorphous α Al at different neodymium concentrations were calculated too. The addition of neodymium increases the amorphizablity of α Al by increasing the incubation time and decreasing the nucleation rate and the critical cooling rate. The calculations are fitted to experimental results when liquidus temperatures are estimated from an approximation, which treats Al Fe V Si Nd as quasi binary Al Fe system.
