The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinemen...The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinement limitation with very high strains. The results show that the fine grain zone in the center of sample expands gradually with the increase of forging passes. When the forging passes reach 6, an X-shape fine grain zone is initially formed. With a further increase of the passes, this X-shape zone tends to spread the whole sample. Limitation in the structural refinement is observed with increasing strains during multi-forging process at the room temperature. The grains size in the center is refined to a certain size （110 μm as forging passes reach 12, and there is no further grain refinement in the center with increasing the forging passes to 24. However, the size of the coarse grains near the surface is continuously decreased with increasing the forging passes to 24.展开更多
The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and ...The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture.展开更多
In this paper the solidification behavior of Sn-Sb peritectic alloy and the mechanism of grain refinement in solidification process under high-intensity ultrasonic field are investigated. Three different powers of hig...In this paper the solidification behavior of Sn-Sb peritectic alloy and the mechanism of grain refinement in solidification process under high-intensity ultrasonic field are investigated. Three different powers of high-intensity ultrasound are introduced into molten Sn-Sb peritectic alloy to study the refining effectiveness. The results show that the application of high-intensity ultrasound during solidification process of Sn-Sb peritectic alloy can refine α phase and β phase and eliminate gravity segregation of the alloy. As acoustic intensity is increased from 400 W to 800 W, not only the homogenous fine structure can be obtained, but also the cubic β phase crystals tend to be spherical. Microstructure of the sample treated by 600 W high-intensity ultrasound demonstrates the best refining effect.展开更多
The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion....The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclu- sions Ce_(2)O_(3)and Ce_(2)O_(2)S. Ce addition led to noticeable refinement of both the dendrite structure and σphase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σphase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure re- finement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σphase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σphase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.展开更多
The ridging defect on the surface of stainless steel products is related to the solidification structure of ferritic stainless steel.Refining the solidification structure and increasing the proport io n of equiaxed gr...The ridging defect on the surface of stainless steel products is related to the solidification structure of ferritic stainless steel.Refining the solidification structure and increasing the proport io n of equiaxed grains are necessary to lesse n the ridging defect.Therefore,a new idea of using a heterogeneous nucieating agent which was composed of the composite core containing Ti was proposed,that is,a large amount of dispersed fine particles were initially formed on the solidification front,and a great amount ofδiron was then nucleated using these fine particles as the heterogeneous cores.Through analyzing the crystallographic relationship between different crystals and inducing the calculation formulas of disregistry,the disregistry between the different oxides and TiNδiron was explored and the type of nucleation core was determined.The key parameters of forming the composite core containing Ti were obtained through a thermodynamic calculatio n.The experimental results further con firm the correctness of the theoretical analysis.展开更多
The Cu65Ni35,Cu60Ni40 and Cu55Ni45 alloys were undercooled by fluxing method,and the rapid solidification structure with different undercoolings were also obtained.At the same time,the interface migration process duri...The Cu65Ni35,Cu60Ni40 and Cu55Ni45 alloys were undercooled by fluxing method,and the rapid solidification structure with different undercoolings were also obtained.At the same time,the interface migration process during rapid solidification was photographed by high-speed photography,and the relationship between the morphological characteristics of solidification front and undercooling was analyzed.The microstructures of the three alloys were observed by metallographic microscope,and the microstructure characteristics and evolution law were systematically studied.It was found that two grain refinement events occurred in the low undercooling range and high undercooling range,respectively.The EBSD test of grain refined microstructures showed that the microstructure in the low undercooling range has a high proportion of low-angle grain boundaries and high strength textures.However,there were a large proportion of high-angle grain boundaries and a high proportion of twin grain boundaries and more randomly oriented grains in the microstructure in the high undercooling range.The TEM test of the Cu55Ni45 alloy with the maximum undercooling of 284 K showed that there were high-density dislocation networks and stacking faults in the grains.Finally,the evolution relationship between microstructure hardness and undercooling was systematically studied.It was found that the microhardness of the three alloys decreased sharply near the critical undercooling.Combined with EBSD,TEM and microhardness analysis,it was confirmed that the grain refinement under low undercooling was caused by dendrite remelting,while the grain refinement under high undercooling was caused by stress-induced recrystallization.展开更多
QPA (Quantitative Phase Analysis) of carbonate rocks bearing calcite and dolomite using X-ray diffractometry (XRD) can be performed using the combined Rietveld Structure Refinement (RSR) and semiquantitative Reference...QPA (Quantitative Phase Analysis) of carbonate rocks bearing calcite and dolomite using X-ray diffractometry (XRD) can be performed using the combined Rietveld Structure Refinement (RSR) and semiquantitative Reference Intensity Ratio (RIR) methods, providing an estimation of crystalline phase in a mixture. Different ratios of five samples were prepared by mixing these crystal minerals with high sensitively. The scan speeds, adequate to determine mineral phases in rock samples, were used as 6 degrees per minute with 0.08 steps. The XRD analysis with commercial TOPAS 3.0 program, defined by a new generation of profile and structure analysis software, based on RSR provides Bragg reflection profiles and the dimension of the unit cell of a phase. The weight fractions of each phase were found by Le Bail and Pawley methods in RSR using a pseudo-Voigt peak shape model. The samples were also characterized by using X-ray fluorescence (XRF) and atomic absorption spectrometer (AAS). These analyses were conducted to compare these results with those obtained from the RSR. In addition to these, RSR of phases is very important to improve the goodness of fit (GOF). Therefore, the discussions of refinement of the carbonate mixing were made and a refinement procedure was given for these mixing in detail. Taking advantage of the RSR with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, has been accurately determined. RSR technique offers a valid support for the characterization of marble in the light of industrial products.展开更多
Although stolzite was discovered in Yaogangxian, Hunan Province, China, in 1948, no formal report about this mineral has been published. Recently its crystal structure has been refined by means of the Rietveld method....Although stolzite was discovered in Yaogangxian, Hunan Province, China, in 1948, no formal report about this mineral has been published. Recently its crystal structure has been refined by means of the Rietveld method. The cell dimensions of the mineral are: a=b= 0.544503(3) nm, c= 1.20495(1)nm and α=β=γ=90° . The X, Y and Z coordinates of the atom O refined by the authors are 0.2637, 0.1137 and 0.0706, respectively. The length of the W-O bond is 0.17826 nm and the angle of the O-W-O bound are 123° and 103° ,respectively.展开更多
The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constant...The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constants a =0 48912(3) nm, c =1 973(2) nm and D x=8 974 g·cm -3 . The Rietveld structural refinement was performed, leading to R p=0 138 and R wp =0 185. The figure of merit F N for the XRD data is F 30 =82 1(0 0068, 54). The X ray powder diffraction data are presented.展开更多
The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and r...The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and reliability factors were refined to be a=6.268 3(1), V=246.29^(3), Z=4, D_(x)=9.377 g/cm^3, R_(B)=3.57%, R_(F)=3.64%, R_(p)=6.63%, R_(WP)=8.80%.展开更多
Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change o...Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(DT)was systematically studied.It was found that the two alloys experienced the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The experimental results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,whereas,the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscope(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it can be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.展开更多
Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change o...Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(ΔT)was systematically studied.It is found that the two alloys experience the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,but the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscopy(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it could be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.On this basis,in the processing of copper base alloys,there will be serious work hardening phenomenon and machining hard problem of consciousness problems caused by excessive cutting force.A twodimensional orthogonal turning finite element model was established using ABAQUS software to analyze the changes in cutting speed and tool trajectory in copper based alloy ultrasonic elliptical vibration turning.The results show that in copper based alloy ultrasonic elliptical vibration turning,cutting process parameters have a significant impact on cutting force.Choosing reasonable process parameters can effectively reduce cutting force and improve machining quality.展开更多
The Al-5Ti-0.2C-based grain refiners with different contents of rare earth （RE） were successfully prepared via powder metallurgy and vacuum casting. The microstructural evolution has been studied by X-ray diffracti...The Al-5Ti-0.2C-based grain refiners with different contents of rare earth （RE） were successfully prepared via powder metallurgy and vacuum casting. The microstructural evolution has been studied by X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results showed that the RE addition resulted in the formation of TiAl3/Ti2Al20RE core-shell structured primary particles, and the size of TiAl3 core decreased, while the thickness of Ti2Al20RE increased with increase of RE contents. As compared to Al-5Ti-0.2C grain refiner, the grain refining efficiency was gradually improved with increase of RE contents, which was mainly attributed to the TiAl3/Ti2Al20RE core-shell structured primary particles and insoluble TiC nuclei formed inα-Al matrix. The formation mechanism of core-shell structure was further investigated based on Ginstling-Brounstein model.展开更多
Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central p...Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central part of the impeller is disk- or plate-shaped, and the blades are fitted to the side of the disk or plate. In addition, a disk is put on the top side of the impeller blades. The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller. These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller. In addition, the sloped swept-back impeller requires less power consumption. The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidi- rectional impeller rotation and without installing baffles. The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath. Highly efficient gas injection refining can be established under the conditions of proper impeller size, larger nozzle immersion depth, larger eccen- tricity and rotation speed of the impeller. The sloped swept back blade impeller can decrease the power consumption and vet improve the bubble disintegration and wide dist^ersion in the bath.展开更多
Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification ...Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification structure was further investigated.With adding 0.0023%La,the Al_(2)O_(3)·CaO·CaS inclusions were modified to the LaAlO_(3)·CaO·CaS inclusions.Additionally,the morphology tended to be more spherical,and the proportion of small-sized inclusions increased significantly from 77.8%to 93.5%.The large-sized inclusions were almost completely eliminated.Based on experimental results,a dynamical model elucidating the process of inclusion modification by La was developed.Furthermore,the ratio of equiaxed zone of the solidification structure increased from 22.9%to 31.0%,and the average primary dendrite arm spacing decreased significantly from 288.4 to 226.2μm.Two-dimensional lattice mismatch analysis results determined that LaAlO_(3)can serve as an effective heterogeneous nucleation core,leading to solidification structure refinement.The beneficial transformation of inclusions and refinement of solidification structure are conducive to the cold heading process of 40Cr steel.展开更多
This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC a...This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.展开更多
Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal.In this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu ...Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal.In this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu Basin,and low-temperature liquid-nitrogen adsorption(LP-N2A)measurements were taken under various pretreatment temperatures.Owing to the continuous loss of water and volatile matter in low-rank coal,the total pore volume assumes a three-step profile with knee temperatures of 150°C and 240°C.However,the ash in the coal can protect the coal skeleton.Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm.Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume,whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures(<150°C)followed by a faint decrease.As for mesopores with apertures larger than 10 nm,the pore volume increases significantly when the pretreatment temperature reaches 300°C.The pore structure of low-rank coal features a significant heating effect,the pretreatment temperature should not exceed 150°C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.展开更多
Disc refiner is a critical equipment in the pulping and papermaking industry,pulp is refined in the refining zone,and different bar structures of refining disc constitute the different refining zones.With the use of t...Disc refiner is a critical equipment in the pulping and papermaking industry,pulp is refined in the refining zone,and different bar structures of refining disc constitute the different refining zones.With the use of the 3D modeling software SOLIDWORKS,five different refining discs that are commonly used in low consistency pulping,were built.The five refining discs were simulated and analyzed using the Computational Fluid Dynamics(CFD)software.The distribution of pulp velocity and surface shear stress,which is displayed between the bar and groove structures,can indirectly show the stress conditions on the refining discs.This paper provides a theoretical basis for research on the bar and groove failure of the refining discs.展开更多
基金Projects(51204053,51074048,51204048)supported by the National Natural Science Foundation of ChinaProject(20110491518)supported by China Postdoctoral Science FoundationProject(2012CB619506)supported by the National Basic Research Program of China
文摘The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinement limitation with very high strains. The results show that the fine grain zone in the center of sample expands gradually with the increase of forging passes. When the forging passes reach 6, an X-shape fine grain zone is initially formed. With a further increase of the passes, this X-shape zone tends to spread the whole sample. Limitation in the structural refinement is observed with increasing strains during multi-forging process at the room temperature. The grains size in the center is refined to a certain size （110 μm as forging passes reach 12, and there is no further grain refinement in the center with increasing the forging passes to 24. However, the size of the coarse grains near the surface is continuously decreased with increasing the forging passes to 24.
基金Project supported by the National Natural Science Foundation of China(51571084 and 51171059)Project of Scientific And Technological Research In Henan Province(152102210072)
文摘The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture.
文摘In this paper the solidification behavior of Sn-Sb peritectic alloy and the mechanism of grain refinement in solidification process under high-intensity ultrasonic field are investigated. Three different powers of high-intensity ultrasound are introduced into molten Sn-Sb peritectic alloy to study the refining effectiveness. The results show that the application of high-intensity ultrasound during solidification process of Sn-Sb peritectic alloy can refine α phase and β phase and eliminate gravity segregation of the alloy. As acoustic intensity is increased from 400 W to 800 W, not only the homogenous fine structure can be obtained, but also the cubic β phase crystals tend to be spherical. Microstructure of the sample treated by 600 W high-intensity ultrasound demonstrates the best refining effect.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. U1860204, 52004061)Talent Project of Revitalizing Liaoning (Grant No. XLYC1802101)+2 种基金Project funded by China Postdoctoral Science Foundation (Grant No. 2020M670777)Northeastern University Postdoctoral Funds (Grant No. 20200321)Fundamental Research Funds for the Central Universities (Grant No. N2125017)。
文摘The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclu- sions Ce_(2)O_(3)and Ce_(2)O_(2)S. Ce addition led to noticeable refinement of both the dendrite structure and σphase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σphase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure re- finement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σphase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σphase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.
基金National Natural Science Foundation of China(Grant Nos.51504001 and 51574001).
文摘The ridging defect on the surface of stainless steel products is related to the solidification structure of ferritic stainless steel.Refining the solidification structure and increasing the proport io n of equiaxed grains are necessary to lesse n the ridging defect.Therefore,a new idea of using a heterogeneous nucieating agent which was composed of the composite core containing Ti was proposed,that is,a large amount of dispersed fine particles were initially formed on the solidification front,and a great amount ofδiron was then nucleated using these fine particles as the heterogeneous cores.Through analyzing the crystallographic relationship between different crystals and inducing the calculation formulas of disregistry,the disregistry between the different oxides and TiNδiron was explored and the type of nucleation core was determined.The key parameters of forming the composite core containing Ti were obtained through a thermodynamic calculatio n.The experimental results further con firm the correctness of the theoretical analysis.
文摘The Cu65Ni35,Cu60Ni40 and Cu55Ni45 alloys were undercooled by fluxing method,and the rapid solidification structure with different undercoolings were also obtained.At the same time,the interface migration process during rapid solidification was photographed by high-speed photography,and the relationship between the morphological characteristics of solidification front and undercooling was analyzed.The microstructures of the three alloys were observed by metallographic microscope,and the microstructure characteristics and evolution law were systematically studied.It was found that two grain refinement events occurred in the low undercooling range and high undercooling range,respectively.The EBSD test of grain refined microstructures showed that the microstructure in the low undercooling range has a high proportion of low-angle grain boundaries and high strength textures.However,there were a large proportion of high-angle grain boundaries and a high proportion of twin grain boundaries and more randomly oriented grains in the microstructure in the high undercooling range.The TEM test of the Cu55Ni45 alloy with the maximum undercooling of 284 K showed that there were high-density dislocation networks and stacking faults in the grains.Finally,the evolution relationship between microstructure hardness and undercooling was systematically studied.It was found that the microhardness of the three alloys decreased sharply near the critical undercooling.Combined with EBSD,TEM and microhardness analysis,it was confirmed that the grain refinement under low undercooling was caused by dendrite remelting,while the grain refinement under high undercooling was caused by stress-induced recrystallization.
文摘QPA (Quantitative Phase Analysis) of carbonate rocks bearing calcite and dolomite using X-ray diffractometry (XRD) can be performed using the combined Rietveld Structure Refinement (RSR) and semiquantitative Reference Intensity Ratio (RIR) methods, providing an estimation of crystalline phase in a mixture. Different ratios of five samples were prepared by mixing these crystal minerals with high sensitively. The scan speeds, adequate to determine mineral phases in rock samples, were used as 6 degrees per minute with 0.08 steps. The XRD analysis with commercial TOPAS 3.0 program, defined by a new generation of profile and structure analysis software, based on RSR provides Bragg reflection profiles and the dimension of the unit cell of a phase. The weight fractions of each phase were found by Le Bail and Pawley methods in RSR using a pseudo-Voigt peak shape model. The samples were also characterized by using X-ray fluorescence (XRF) and atomic absorption spectrometer (AAS). These analyses were conducted to compare these results with those obtained from the RSR. In addition to these, RSR of phases is very important to improve the goodness of fit (GOF). Therefore, the discussions of refinement of the carbonate mixing were made and a refinement procedure was given for these mixing in detail. Taking advantage of the RSR with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, has been accurately determined. RSR technique offers a valid support for the characterization of marble in the light of industrial products.
文摘Although stolzite was discovered in Yaogangxian, Hunan Province, China, in 1948, no formal report about this mineral has been published. Recently its crystal structure has been refined by means of the Rietveld method. The cell dimensions of the mineral are: a=b= 0.544503(3) nm, c= 1.20495(1)nm and α=β=γ=90° . The X, Y and Z coordinates of the atom O refined by the authors are 0.2637, 0.1137 and 0.0706, respectively. The length of the W-O bond is 0.17826 nm and the angle of the O-W-O bound are 123° and 103° ,respectively.
文摘The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constants a =0 48912(3) nm, c =1 973(2) nm and D x=8 974 g·cm -3 . The Rietveld structural refinement was performed, leading to R p=0 138 and R wp =0 185. The figure of merit F N for the XRD data is F 30 =82 1(0 0068, 54). The X ray powder diffraction data are presented.
文摘The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and reliability factors were refined to be a=6.268 3(1), V=246.29^(3), Z=4, D_(x)=9.377 g/cm^3, R_(B)=3.57%, R_(F)=3.64%, R_(p)=6.63%, R_(WP)=8.80%.
基金Funded by the Basic Research Projects in Shanxi Province(No.202103021224183)。
文摘Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(DT)was systematically studied.It was found that the two alloys experienced the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The experimental results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,whereas,the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscope(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it can be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.
基金Funded by the Basic Research Projects in Shanxi Province(202103021224183)。
文摘Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(ΔT)was systematically studied.It is found that the two alloys experience the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,but the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscopy(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it could be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.On this basis,in the processing of copper base alloys,there will be serious work hardening phenomenon and machining hard problem of consciousness problems caused by excessive cutting force.A twodimensional orthogonal turning finite element model was established using ABAQUS software to analyze the changes in cutting speed and tool trajectory in copper based alloy ultrasonic elliptical vibration turning.The results show that in copper based alloy ultrasonic elliptical vibration turning,cutting process parameters have a significant impact on cutting force.Choosing reasonable process parameters can effectively reduce cutting force and improve machining quality.
基金Project supported by National High Technology Research and Development Program of China(2013AA031001)the National Basic Research Program of China(2012CB619503)International Science&Technology Cooperation Program of China(2012DFA50630)
文摘The Al-5Ti-0.2C-based grain refiners with different contents of rare earth （RE） were successfully prepared via powder metallurgy and vacuum casting. The microstructural evolution has been studied by X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results showed that the RE addition resulted in the formation of TiAl3/Ti2Al20RE core-shell structured primary particles, and the size of TiAl3 core decreased, while the thickness of Ti2Al20RE increased with increase of RE contents. As compared to Al-5Ti-0.2C grain refiner, the grain refining efficiency was gradually improved with increase of RE contents, which was mainly attributed to the TiAl3/Ti2Al20RE core-shell structured primary particles and insoluble TiC nuclei formed inα-Al matrix. The formation mechanism of core-shell structure was further investigated based on Ginstling-Brounstein model.
基金Item Sponsored by National Natural Science Foundation of China(50974035,51074047)National High Technology Research and Development Program(863 Program)of China(2010AA03A405,2012AA062303)Innovation Team Project of Provincial Science and Technology of Liaoning Province of China(LT2010034)
文摘Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central part of the impeller is disk- or plate-shaped, and the blades are fitted to the side of the disk or plate. In addition, a disk is put on the top side of the impeller blades. The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller. These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller. In addition, the sloped swept-back impeller requires less power consumption. The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidi- rectional impeller rotation and without installing baffles. The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath. Highly efficient gas injection refining can be established under the conditions of proper impeller size, larger nozzle immersion depth, larger eccen- tricity and rotation speed of the impeller. The sloped swept back blade impeller can decrease the power consumption and vet improve the bubble disintegration and wide dist^ersion in the bath.
基金the National Natural Science Foundation of China(52004180,52204350)the China Postdoctoral Science Foundation(2020M683706XB)the Research Project Supported by Shanxi Scholarship Council of China(2023-080).
文摘Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification structure was further investigated.With adding 0.0023%La,the Al_(2)O_(3)·CaO·CaS inclusions were modified to the LaAlO_(3)·CaO·CaS inclusions.Additionally,the morphology tended to be more spherical,and the proportion of small-sized inclusions increased significantly from 77.8%to 93.5%.The large-sized inclusions were almost completely eliminated.Based on experimental results,a dynamical model elucidating the process of inclusion modification by La was developed.Furthermore,the ratio of equiaxed zone of the solidification structure increased from 22.9%to 31.0%,and the average primary dendrite arm spacing decreased significantly from 288.4 to 226.2μm.Two-dimensional lattice mismatch analysis results determined that LaAlO_(3)can serve as an effective heterogeneous nucleation core,leading to solidification structure refinement.The beneficial transformation of inclusions and refinement of solidification structure are conducive to the cold heading process of 40Cr steel.
文摘This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.
基金This work was supported by the Natural Science Basic Research Plan in Shaanxi Province of China(Program No.2019JQ-527)Shandong Key laboratory of Depositional Mineralization and Sedimentary Mineral Open Fund(Program No.DMSM20190014)Scientific Research Program Funded by Shaanxi Provincial Education Department(Program No.20JS116)。
文摘Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal.In this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu Basin,and low-temperature liquid-nitrogen adsorption(LP-N2A)measurements were taken under various pretreatment temperatures.Owing to the continuous loss of water and volatile matter in low-rank coal,the total pore volume assumes a three-step profile with knee temperatures of 150°C and 240°C.However,the ash in the coal can protect the coal skeleton.Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm.Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume,whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures(<150°C)followed by a faint decrease.As for mesopores with apertures larger than 10 nm,the pore volume increases significantly when the pretreatment temperature reaches 300°C.The pore structure of low-rank coal features a significant heating effect,the pretreatment temperature should not exceed 150°C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.
文摘Disc refiner is a critical equipment in the pulping and papermaking industry,pulp is refined in the refining zone,and different bar structures of refining disc constitute the different refining zones.With the use of the 3D modeling software SOLIDWORKS,five different refining discs that are commonly used in low consistency pulping,were built.The five refining discs were simulated and analyzed using the Computational Fluid Dynamics(CFD)software.The distribution of pulp velocity and surface shear stress,which is displayed between the bar and groove structures,can indirectly show the stress conditions on the refining discs.This paper provides a theoretical basis for research on the bar and groove failure of the refining discs.
