The formation, thermal stability and mechanical properties of Misch metal （Mm）-based alloy bulk metallic glasses （BMGs） with composition of Mm55Al25Cu10Ni5Co5 were investigated by means of X-ray diffraction, diffe...The formation, thermal stability and mechanical properties of Misch metal （Mm）-based alloy bulk metallic glasses （BMGs） with composition of Mm55Al25Cu10Ni5Co5 were investigated by means of X-ray diffraction, differential scanning calorimetry, differential thermal analysis and compression test. The results indicate that the Mm-based BMGs exhibit a distinct glass transition and a wide supercooled liquid region Δ Tx（ 〉 60 K） before crystallization. The alloy can be fabricated into bulk glassy form of 3 mm in diameter by copper mold casting methods. Compared with the La55Al25Cu10 Ni5Co5 BMG, the Mm55Al25Cu10Ni5Co5 BMG shows higher compression fracture strength and lower cost. A new parameter γ and melting temperature Tl are closely correlated with the glass forming ability （GFA） of Mm-based alloys.展开更多
The magnetic properties and microstructure of sintered R-Fe-B（R, rare earth） magnets with nominal composition of（（PrNd）（1-x）MMx）（30）Fe（bal）B1（x = 0, 0.1.0.2,0.3, 0.4, 0.5 and 0.7; MM, misch metal） prepar...The magnetic properties and microstructure of sintered R-Fe-B（R, rare earth） magnets with nominal composition of（（PrNd）（1-x）MMx）（30）Fe（bal）B1（x = 0, 0.1.0.2,0.3, 0.4, 0.5 and 0.7; MM, misch metal） prepared using dual-alloy method were investigated. For x = 0.3, the maximum energy product（（BH）（max）） of the sintered magnet is higher than 318.4 kJ·m^-3,but intrinsic coercivity（H（cj）） is lower than 351.8 kA·m^-1. The La and Ce contents are obviously different in some matrix-phase grains, which proves that the multi-hard magnetic phases（La, Ce-rich and La, Ce-lean） exist in the magnets. The coercivity is improved by the method of doping PrNd nanoparticles without sacrificing other magnetic properties. An enhancement in coercivity from 517.2 to 872.9 kA·m^-1 is achieved by doping 5 wt% PrNd nanoparticles. Meanwhile, it could exhibit better magnetic properties（remanence Br = 1.332 T.intrinsic coercivity H（cj）= 872.9 kA·m^-1 maximum energy product（BH）（max）=318.6 kJ·m^-3） and make the distribution of the intergranular phase become more homogeneous.展开更多
Double main phase process is applied to fabricate [(Pr, Nd)1 – xMMx]13.8FebalM1.5B5.9 (x = 0.5 and 0.7;M = Cu, Al, Co, and Nb) sintered magnets with high misch metal (MM) content. In comparison to the magnets by sing...Double main phase process is applied to fabricate [(Pr, Nd)1 – xMMx]13.8FebalM1.5B5.9 (x = 0.5 and 0.7;M = Cu, Al, Co, and Nb) sintered magnets with high misch metal (MM) content. In comparison to the magnets by single main phase process, the enhanced magnetic properties have been achieved. For magnets of x = 0.7, Hcj increases to 371.9 kA/m by 60.5%, and (BH)max is significantly enhanced to 253.3 kJ/m3 by 56.9%, compared with those of the single main phase magnets of the same nominal composition. In combination with minor loops and magnetic recoil curves, the property improvement of magnets with double main phase method is well explained. As a result, it is demonstrated that double main phase technology is an effective approach to improve the permanent magnetic properties of MM based sintered magnets.展开更多
The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass （BMG） was investigated by means of differential scanning calorimetry （DSC） in the mode of continuous heating or isothermal annealing. It was f...The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass （BMG） was investigated by means of differential scanning calorimetry （DSC） in the mode of continuous heating or isothermal annealing. It was found that the apparent activation energy Eg, Ex and Ep of the BMG calculated by Kissinger＇s method were 189.58, 170.68 and 170.41 kJ·mol^-1, respectively, which was bigger than those of La55Al25Cu10Ni5Co5 BMG indicating that thermal stability of the former was higher than that of the latter. The local activation energy obtained using Ozawa equation decreased as crystallization proceeded except for the initial stage. The Avrami exponents were calculated to be in the range of 3.26 - 5.23 for different crystallization stages and isothermal temperatures. This implied that crystallization of Mm55Al25Cu10Ni5Co2 BMG was governed by diffusion-controlled three-dimensional growth with either reduced or increased nucleation rate, depending on isothermal temperature. Inconsistency of thermal stability with glass-forming ability for Mm（La）-Al-Cu-Ni-Co BMGs was discussed.展开更多
Mg-10Li-4Al and Mg-10Li-4Al-0.6RE alloys were prepared with vacuum induction melting method. The influence of RE on microstructure and mechanical properties was studied with SEM, XRD and tensile tester. The results sh...Mg-10Li-4Al and Mg-10Li-4Al-0.6RE alloys were prepared with vacuum induction melting method. The influence of RE on microstructure and mechanical properties was studied with SEM, XRD and tensile tester. The results showed that, the addition of RE made the α(Mg) phase disappeared and caused the formation of Al3La phase. And it improved both the tensile strength and elongation percentage of alloys.展开更多
The positron lifetime spectra of severalAl_(93.3-x)Fe_(4.3)V_(0.7)Si_(1.7)Mm_x (x = 0.5%, 1.0%, 3.0%, atom fraction) alloys with differentcontent of misch metal prepared by rapid solidification were measured, and the ...The positron lifetime spectra of severalAl_(93.3-x)Fe_(4.3)V_(0.7)Si_(1.7)Mm_x (x = 0.5%, 1.0%, 3.0%, atom fraction) alloys with differentcontent of misch metal prepared by rapid solidification were measured, and the variations on theinterfacial defects with the content of misch metal were revealed by an analysis of the lifetimeresults. The interface characteristics derived from the lifetime results could be used to give asatisfactory interpretation of the dependence of mechanical properties on the content of mischmetal.展开更多
The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray d...The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.展开更多
The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated.The results indicate that the addition of cerium-rich misch metal ...The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated.The results indicate that the addition of cerium-rich misch metal modifies the microstructure gradually.With the increase of the RE addition,the amount of Mg_(17)Al_(12) decreases while that of Al_(11)(RE)_3 increases,accompanied by grain refinement.When the addition reaches 1.5%,the grain refinement becomes obvious.However,when the addition exceeds 2.0%, Al_(11)(RE)_3 phase coarsens into rod shape and the grain size increases.The tensile properties of the AZ81 at both room temperature and 150℃increase with the addition,and reach their optimal values with the addition of 1.5%.Further increase of the addition to above 2.0%decreases the tensile properties considerably.The tensile fracture of the alloy is characterized by the cleavage of the brittle second phases and ductile dimples of the matrix.展开更多
Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,th...Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,the spherical powder was made successfully with the improved three piece nozzle systems of gas atomization unit. It was found that most of the solidified powders with particles size of less than 50μm in diameter were single crystal and the solidification structure of rapidly solidified powders showed a typical dendritic morphology because of supercooling prior to nucleation.The spacing of secondary denrite arms was deceasing as the size of powders was decreasing.The rapidly solidified powders were consolidated by vacuum hot extrusion and the effects of misch metal addition to AZ91 on mechanical properties of extruded bars were also examined.During extrusion of the rapidly solidified powders,their dendritic structure was broken into fragments and remained as grains of about 3μm in size.The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were finely broken,too.The tensile strength and ductility obtained in as-extruded Mg-9 wt pct Al-1 wt pct Zn-3 wt pct MM alloy wereσ-（T.S.） =383 MPa andε=10.6%,respectively.All of these improvements on mechanical properties were resulted from the refined microstructure and second-phase dispersions.展开更多
MM_（33）Fe_（66）B（MM=La, Ce, Pr, Nd） alloys（mass ratio） were prepared by induction melting and heat-treated at 1353 K for 24 h to produce homogeneous MM_2Fe_（14） B phase. The phase structure and element distri...MM_（33）Fe_（66）B（MM=La, Ce, Pr, Nd） alloys（mass ratio） were prepared by induction melting and heat-treated at 1353 K for 24 h to produce homogeneous MM_2Fe_（14） B phase. The phase structure and element distribution of the alloys were analyzed by X-ray diffraction（XRD） and scanning electron microscope（SEM）. The alloys were applied ball milling to obtain powders with good size distribution and then magnetic aligned in a static magnetic field of 2 T for 4 h, in order to achieve the intrinsic magnetic properties by vibrating sample magnetometer（VSM）. XRD results showed that the alloys were composed of the single 2：14：1 main phase and RE-rich phase, which was similar to Nd_2Fe_（14）B structure. Magnetic measurements showed that the saturation magnetization（Ms） and anisotropy field（HA） of the MM_（33）Fe_（66）B alloy were 11.3 k Gs and 48.4 k Oe, respectively, demonstrating its good potential as permanent magnets. The Curie temperature of the MM_（33）Fe_（66）B alloy was determined as 502.9 K by magnetization-temperature curves. Microstructure observation showed that Nd and Pr were mainly in the 2：14：1 ferromagnetic phase, while La and Ce prefered to aggregate in the RE-rich grain boundary phase, which is beneficial to fabricating（Pr, Nd, MM）_2Fe_（14）B magnets with good magnetic properties.展开更多
文摘The formation, thermal stability and mechanical properties of Misch metal （Mm）-based alloy bulk metallic glasses （BMGs） with composition of Mm55Al25Cu10Ni5Co5 were investigated by means of X-ray diffraction, differential scanning calorimetry, differential thermal analysis and compression test. The results indicate that the Mm-based BMGs exhibit a distinct glass transition and a wide supercooled liquid region Δ Tx（ 〉 60 K） before crystallization. The alloy can be fabricated into bulk glassy form of 3 mm in diameter by copper mold casting methods. Compared with the La55Al25Cu10 Ni5Co5 BMG, the Mm55Al25Cu10Ni5Co5 BMG shows higher compression fracture strength and lower cost. A new parameter γ and melting temperature Tl are closely correlated with the glass forming ability （GFA） of Mm-based alloys.
基金financially supported by the National Key Research and Development Program of China (No.2016YFB0700903)the National Natural Science Foundation of China (No.51571126)+3 种基金the Inner Mongolia Innovative Research Team(No.3400102)the Innovative Science and Technology Project of Inner Mongolia (No.4140300502)the Science and Technology Project of Baotou (Nos.2012R1006 and 2015C2006-13)the Science and Technology Innovation Project of University (No.2014QDL003)
文摘The magnetic properties and microstructure of sintered R-Fe-B（R, rare earth） magnets with nominal composition of（（PrNd）（1-x）MMx）（30）Fe（bal）B1（x = 0, 0.1.0.2,0.3, 0.4, 0.5 and 0.7; MM, misch metal） prepared using dual-alloy method were investigated. For x = 0.3, the maximum energy product（（BH）（max）） of the sintered magnet is higher than 318.4 kJ·m^-3,but intrinsic coercivity（H（cj）） is lower than 351.8 kA·m^-1. The La and Ce contents are obviously different in some matrix-phase grains, which proves that the multi-hard magnetic phases（La, Ce-rich and La, Ce-lean） exist in the magnets. The coercivity is improved by the method of doping PrNd nanoparticles without sacrificing other magnetic properties. An enhancement in coercivity from 517.2 to 872.9 kA·m^-1 is achieved by doping 5 wt% PrNd nanoparticles. Meanwhile, it could exhibit better magnetic properties（remanence Br = 1.332 T.intrinsic coercivity H（cj）= 872.9 kA·m^-1 maximum energy product（BH）（max）=318.6 kJ·m^-3） and make the distribution of the intergranular phase become more homogeneous.
基金Project supported by the National Natural Foundation of China(Grant Nos.51590880,11564030,and 51571126)the National Key Research Program of China(Grant No.2016YFB0700903)+3 种基金Fujian Institute of Innovation,Chinese Academy of Sciences(Grant No.FJCXY18040302)the Key Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05-1)the Inner Mongolia Science and Technology Major Project of 2016,Chinathe Natural Science Foundation of Inner Mongolia,China(Grant Nos.2018LH05006 and 2018LH05011)。
文摘Double main phase process is applied to fabricate [(Pr, Nd)1 – xMMx]13.8FebalM1.5B5.9 (x = 0.5 and 0.7;M = Cu, Al, Co, and Nb) sintered magnets with high misch metal (MM) content. In comparison to the magnets by single main phase process, the enhanced magnetic properties have been achieved. For magnets of x = 0.7, Hcj increases to 371.9 kA/m by 60.5%, and (BH)max is significantly enhanced to 253.3 kJ/m3 by 56.9%, compared with those of the single main phase magnets of the same nominal composition. In combination with minor loops and magnetic recoil curves, the property improvement of magnets with double main phase method is well explained. As a result, it is demonstrated that double main phase technology is an effective approach to improve the permanent magnetic properties of MM based sintered magnets.
基金Project supported by the National Natural Science Foundation of Liaoning Province (20032137)
文摘The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass （BMG） was investigated by means of differential scanning calorimetry （DSC） in the mode of continuous heating or isothermal annealing. It was found that the apparent activation energy Eg, Ex and Ep of the BMG calculated by Kissinger＇s method were 189.58, 170.68 and 170.41 kJ·mol^-1, respectively, which was bigger than those of La55Al25Cu10Ni5Co5 BMG indicating that thermal stability of the former was higher than that of the latter. The local activation energy obtained using Ozawa equation decreased as crystallization proceeded except for the initial stage. The Avrami exponents were calculated to be in the range of 3.26 - 5.23 for different crystallization stages and isothermal temperatures. This implied that crystallization of Mm55Al25Cu10Ni5Co2 BMG was governed by diffusion-controlled three-dimensional growth with either reduced or increased nucleation rate, depending on isothermal temperature. Inconsistency of thermal stability with glass-forming ability for Mm（La）-Al-Cu-Ni-Co BMGs was discussed.
基金National Hi-Tech Research Development Programof China (2006AA03Z511)Heilongjian Province Education Commission Science &Technology Research Project (11523018)Harbin Engineering University Fundamental Research Funding Project (002100260739)
文摘Mg-10Li-4Al and Mg-10Li-4Al-0.6RE alloys were prepared with vacuum induction melting method. The influence of RE on microstructure and mechanical properties was studied with SEM, XRD and tensile tester. The results showed that, the addition of RE made the α(Mg) phase disappeared and caused the formation of Al3La phase. And it improved both the tensile strength and elongation percentage of alloys.
基金This work is supported by the National Natural Science Foundation of China (No. 59771020)
文摘The positron lifetime spectra of severalAl_(93.3-x)Fe_(4.3)V_(0.7)Si_(1.7)Mm_x (x = 0.5%, 1.0%, 3.0%, atom fraction) alloys with differentcontent of misch metal prepared by rapid solidification were measured, and the variations on theinterfacial defects with the content of misch metal were revealed by an analysis of the lifetimeresults. The interface characteristics derived from the lifetime results could be used to give asatisfactory interpretation of the dependence of mechanical properties on the content of mischmetal.
基金Project supported by the National Natural Science Foundation of China(Grant No.51590880)the National Key Research and Development Program of China(Grant Nos.2014CB643702 and 2016YFB0700903)+1 种基金Key Research Program of the Chinese Academy of Sciences of Chinathe Inner Mongolia Science and Technology Major Project of China 2016
文摘The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.
基金Project(2007CB613702)supported by the National Basic Research Program of ChinaProject(2006BA104B04-2)supported byChongqing S&T Research Program,China
文摘The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated.The results indicate that the addition of cerium-rich misch metal modifies the microstructure gradually.With the increase of the RE addition,the amount of Mg_(17)Al_(12) decreases while that of Al_(11)(RE)_3 increases,accompanied by grain refinement.When the addition reaches 1.5%,the grain refinement becomes obvious.However,when the addition exceeds 2.0%, Al_(11)(RE)_3 phase coarsens into rod shape and the grain size increases.The tensile properties of the AZ81 at both room temperature and 150℃increase with the addition,and reach their optimal values with the addition of 1.5%.Further increase of the addition to above 2.0%decreases the tensile properties considerably.The tensile fracture of the alloy is characterized by the cleavage of the brittle second phases and ductile dimples of the matrix.
文摘Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,the spherical powder was made successfully with the improved three piece nozzle systems of gas atomization unit. It was found that most of the solidified powders with particles size of less than 50μm in diameter were single crystal and the solidification structure of rapidly solidified powders showed a typical dendritic morphology because of supercooling prior to nucleation.The spacing of secondary denrite arms was deceasing as the size of powders was decreasing.The rapidly solidified powders were consolidated by vacuum hot extrusion and the effects of misch metal addition to AZ91 on mechanical properties of extruded bars were also examined.During extrusion of the rapidly solidified powders,their dendritic structure was broken into fragments and remained as grains of about 3μm in size.The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were finely broken,too.The tensile strength and ductility obtained in as-extruded Mg-9 wt pct Al-1 wt pct Zn-3 wt pct MM alloy wereσ-（T.S.） =383 MPa andε=10.6%,respectively.All of these improvements on mechanical properties were resulted from the refined microstructure and second-phase dispersions.
基金Project supported by the National High Technology Research and Development Program of China(2012AA063201)National Natural Science Foundation of China(51371002+2 种基金51331003)International S&T Cooperation Program of China(2015DFG52020)the 2011 Cooperative Innovation Center of Beijing University of Technology
文摘MM_（33）Fe_（66）B（MM=La, Ce, Pr, Nd） alloys（mass ratio） were prepared by induction melting and heat-treated at 1353 K for 24 h to produce homogeneous MM_2Fe_（14） B phase. The phase structure and element distribution of the alloys were analyzed by X-ray diffraction（XRD） and scanning electron microscope（SEM）. The alloys were applied ball milling to obtain powders with good size distribution and then magnetic aligned in a static magnetic field of 2 T for 4 h, in order to achieve the intrinsic magnetic properties by vibrating sample magnetometer（VSM）. XRD results showed that the alloys were composed of the single 2：14：1 main phase and RE-rich phase, which was similar to Nd_2Fe_（14）B structure. Magnetic measurements showed that the saturation magnetization（Ms） and anisotropy field（HA） of the MM_（33）Fe_（66）B alloy were 11.3 k Gs and 48.4 k Oe, respectively, demonstrating its good potential as permanent magnets. The Curie temperature of the MM_（33）Fe_（66）B alloy was determined as 502.9 K by magnetization-temperature curves. Microstructure observation showed that Nd and Pr were mainly in the 2：14：1 ferromagnetic phase, while La and Ce prefered to aggregate in the RE-rich grain boundary phase, which is beneficial to fabricating（Pr, Nd, MM）_2Fe_（14）B magnets with good magnetic properties.
