NiMnGaferromagnetic shape memory thin film was deposited onto Al foil using r.f.magnetron sputtering technique.The crystallization behavior of the film was investigated by XRD and DSC.The activation energy of crystall...NiMnGaferromagnetic shape memory thin film was deposited onto Al foil using r.f.magnetron sputtering technique.The crystallization behavior of the film was investigated by XRD and DSC.The activation energy of crystallization of the film was calculated by Kissinger’s method.The results show that the crystallization temperature of NiMnGafree-standing thin film in martensite state is 372 ℃,and the activation energy of crystallization is about 191.9 kJ·mol-1.展开更多
A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga a...A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga alloy, the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe-Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved.展开更多
The effect of Co content on magnetic property and phase stability of Ni50-xMn25Ga25Cox ferromagnetic shape memory alloys has been investigated using first-principles calculations. The total energy difference between p...The effect of Co content on magnetic property and phase stability of Ni50-xMn25Ga25Cox ferromagnetic shape memory alloys has been investigated using first-principles calculations. The total energy difference between paramagnetic and ferromagnetic state of austenite plays an important role in the magnetic transition. The high Curie temperature can be attributed to the stronger Co-Mn exchange interaction as compared to the Ni-Mn one. The phase stability of Niso-xMn25Ga25Cox austenite increases with increasing Co content, which is discussed based on the electronic structure.展开更多
The martensitic transformation in Co37Ni34Al29 ribbon is characterized in detail by means of in-situ thermostatic x-ray diffraction and magnetic measurements.The results show a structural transition from the body-cent...The martensitic transformation in Co37Ni34Al29 ribbon is characterized in detail by means of in-situ thermostatic x-ray diffraction and magnetic measurements.The results show a structural transition from the body-centred cubic to martensite with a tetragonal structure during cooling.Comparison between the results of the diffraction intensity with the magnetic susceptibility measurements indicates that the martensitic transformation takes place in several different steps during cooling from 273 to 163 K.During heating from 313 to 873 K,the peak width becomes very wide and the intensity turns very low.The γ-phase （face-centred cubic structure） emerges and increases gradually with temperature increasing from 873 to 1073 K.展开更多
The influence of stresses on martensitic transformation in Ni50Mn19Fe6Ga25 melt-spun ribbons was studied. X-ray diffraction examination shows that the ribbon has a pure cubic L21 phase at room temperature and that the...The influence of stresses on martensitic transformation in Ni50Mn19Fe6Ga25 melt-spun ribbons was studied. X-ray diffraction examination shows that the ribbon has a pure cubic L21 phase at room temperature and that the ribbon surface exhibits [100] preferentially oriented texture, while the [110] axis is about 45° tilted from the normal of the ribbon. By calculating the d spacing at different angles with the length direction of the ribbon, the tension was observed. It was found that the direction of the stress was along [010] direction of the oriented textured grains. During cooling, there is no obvious structural transition observed in as-spun ribbons. However, when the ribbons were annealed at 900 K for 24 h, the tension along [010] direction disappeared and the structural transition from cubic to tetragonal occurred obviously during cooling. It indicates that it is the tension along [010] direction to suppress the martensitic transformation in the as-spun ribbons.展开更多
The effect of Co substitution on magnetic properties of Ni-Mn-Sn shape memory alloy was revealed by first-principles calculations. Large magnetization difference in Ni-Mn-Sn alloy obtained by addition of Co arises fro...The effect of Co substitution on magnetic properties of Ni-Mn-Sn shape memory alloy was revealed by first-principles calculations. Large magnetization difference in Ni-Mn-Sn alloy obtained by addition of Co arises from enhancement of magnetization of austenite due to change of Mn-Mn interaction from anti-ferromagnetism to ferromagnetism. Total energy difference between paramagnetic and ferromagnetic austenite plays an important role in magnetic transition of Ni-Co-Mn-Sn. The altered Mn 3d states due to Co substitution give rise to difference in magnetic properties.展开更多
The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （...The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （FSMA） composite and hybrid mechanism that can provide a fast response and a strong thrust. The caudal peduncle actuator was inspired by Scomber Scombrus which utilises thunniform mode swimming, which is the most efficient locomotion mode evolved in the aquatic environment, where the thrust is generated by the lift-based method, allowing high cruising speeds to be maintained for a long period of time. The morphology of an average size Scomber Scombrus （length in 310 mm） was investigated, and a 1：1 scale caudal peduncle actuator prototype was modelled and fabricated. The propulsive wave characteristics of the fish at steady speeds were employed as initial design objectives. Some key design parameters are investigated, i.e. aspect ratio （AR） （AR = 3.49）, Reynolds number （Re = 429 649）, reduced frequency （σ = 1.03）, Strouhal number （St = 0.306） and the maximum strain of the bent tail was estimated at ε = 1.11% which is in the range of superelasticity. The experimental test of the actuator was carried out in a water tank. By applying 7 V and 2.5 A, the actuator can reach the tip-to-tip rotational angle of 85° at 4 Hz.展开更多
The mechanism for the effects of pressure on the magnetic properties and the martensitic transformation of Ni-Mn- Sn shape memory alloys is revealed by first-principles calculations. It is found that the total energy ...The mechanism for the effects of pressure on the magnetic properties and the martensitic transformation of Ni-Mn- Sn shape memory alloys is revealed by first-principles calculations. It is found that the total energy difference between paramagnetic and ferromagnetic austenite states plays an important role in the magnetic transition of Ni-Mn-Sn under pressure. The pressure increases the relative stability of the martensite with respect to the anstenite, leading to an increase of the martensitic transformation temperature. Moreover, the effects of pressure on the magnetic properties and the martensitic transformation are discussed based on the electronic structure.展开更多
The total energy, electronic structures, and magnetisms of the Al Cu2Mn-type Co2TiSb1-xSnx（x = 0, 0.25, 0.5） with the different lattice parameter ratios of c/a are studied by using the first-principles calculations....The total energy, electronic structures, and magnetisms of the Al Cu2Mn-type Co2TiSb1-xSnx（x = 0, 0.25, 0.5） with the different lattice parameter ratios of c/a are studied by using the first-principles calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, a ferromagnetic shape memory effect can be expected to occur in these alloys. The Al Cu2Mn-type Co2TiSb1-xSnx（x = 0, 0.25, 0.5） alloys are weak ferrimagnets in the austenitic phase and martensitic phase.展开更多
The mutual coupling of structure and magnetism is crucial for Heusler alloys.In this paper,Ni_(50)Mn_(34)Sb_(16-x)Ga_(x)(0≤x≤16)alloys were prepared by arc melting.Based on the test results of structure and magnetis...The mutual coupling of structure and magnetism is crucial for Heusler alloys.In this paper,Ni_(50)Mn_(34)Sb_(16-x)Ga_(x)(0≤x≤16)alloys were prepared by arc melting.Based on the test results of structure and magnetism,the magnetic-structural phase diagram of Ni_(50)Mn_(34)Sb_(16-x)Ga_(x)(0≤x≤16)was drawn.The structure changes from cubic to monoclinic and finally to tetragonal as the x increases at room temperature.Its phase diagram shows a morphotropic phase boundary(MPB)starting from a tricritical triple point(around the Ni_(50)Mn_(34)Sb_(5)Ga_(11)alloy)of a cubic paramagnetic phase,ferromagnetic monoclinic,and antiferromagnetic tetragonal phases.And Ni_(50)Mn_(34)Sb_(5)Ga_(11)alloy has experienced five different phase states:paramagnetic austenite→ferromagnetic austenite→antiferromagnetic martensite→ferromagnetic martensite→spin glass as the temperature decreased.Further study of the alloys’magnetostrictive properties near the MPB showed that as x increases,a negative strain initially appears,followed by a W-type that crosses negative and positive strains,and then a positive strain.This is caused by the inconsistency in the speed and degree of magnetic domain walls response with monoclinic and tetragonal coexisting structures.This indicates that coupling between structure and magnetism is critical to the properties of materials.This work provides valuable insights into the magnetostrictive behavior and structural evolution of Heusler alloys,particularly in the context of MPB systems,and offers guidance for the design and optimization of material properties through controlled magnetic-structural interactions.Kindly check and confirm the edit made in the title.The edit made in the title has been confirmed to be accurate.展开更多
Studies on Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys(FSMAs)have been quite active topics in recent years.Unlike previous reports where the amount of Co doping was generally less than 8 at%,in this work Ni_...Studies on Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys(FSMAs)have been quite active topics in recent years.Unlike previous reports where the amount of Co doping was generally less than 8 at%,in this work Ni_(55-x)Co_(x)Mn_(20)Ga_(25)(8.5≤x≤11.0)alloys were studied with high Co doping.Unusual effects of both composition and magnetic field on phase transitions were observed.With the increase in substitution of Co for Ni,the magnetic transition temperatures increase gradually but the martensitic transformation temperature decreases quite sharply.In particular,the average decrease in the martensitic transformation temperatures is up to 100 K which is nearly twice that in the case of Co content of less than 8 at%.Further,under an applied magnetic field ranging from 0.03 to 0.60 T,abnormal stabilization of a martensite phase with lower magnetization was monitored.Magnetic entropy change of 1.6 J·kg^(−1)·K^(−1)was induced at the martensitic transformation of Ni46.5Co8.5Mn20Ga25 alloy by an applied field of 1 T.The magnetic contributions,including the magnetocrystalline anisotropy and the Zeeman energy,to the thermodynamics of the martensitic transformation are considered to understand the observed unusual phenomena.This work results in new insights into the understanding of Co-doped Ni–Mn-based ferromagnetic shape memory alloys.展开更多
Ni30Cu20Mn37＋xGa13-x（x = 0–4.5） alloys were studied with the phase transformation and mechanical properties. With the increase of Mn content, the martensitic transformation temperatures increase and the Curie temp...Ni30Cu20Mn37＋xGa13-x（x = 0–4.5） alloys were studied with the phase transformation and mechanical properties. With the increase of Mn content, the martensitic transformation temperatures increase and the Curie temperature decreases. Simultaneously, the room temperature microstructure evolves from single phase of austenite to dual phases containing martensite and precipitation. Both the ductility and the strength of the polycrystalline alloys are significantly improved by the precipitation. Coupled magnetostructural transition from weak magnetic martensite to ferromagnetic austenite is obtained in both single-phase and ductile dual-phase alloys.展开更多
This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry （DSC）...This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry （DSC） methods. The structure type of Ni55.5Fe18Ga26.5-xSix alloys is determined by x-ray diffraction （XRD）, and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite （with Si content x = 0） to body-centred cubic austenite （with x = 2） at room temperature. The martensitic transformation temperatures of the Ni55.sFelsGa26.5-xSi~ alloys decrease almost linearly with increasing Si content in the Si content range of x _~ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga^Si alloy. The valence electronic concentrations, size factor, L21 degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.展开更多
A series of Ni-Fe-Ga alloys near the prototype Heusler composition （X2YZ） were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and anneali...A series of Ni-Fe-Ga alloys near the prototype Heusler composition （X2YZ） were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and annealing treatment were studied in detail by an optical microscope, X-ray diffraction, and differential scanning calorimeters methods. The experimental results show that the martensitic transformation temperatures increase almost linearly with increasing Ni content in all the NiFeGa alloys. Annealing the Ni55.5Fe18Ga26.5 alloy at 100-500 ℃ for 3 h and at 300 ℃ for 1-10 h shifts the martensitic transformation start temperature by almost 20 ℃ to high temperature. The variations in the martensitic transformation temperatures in these alloys are discussed in terms of structural differences resulting from alloy composition and annealing treatment.展开更多
The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed si...The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed sintered specimens exhibit typical martensitic transformation behaviours. The martensite of the sintered specimen after annealing exhibits a ferromagnetic nature. Moreover, study of the fracture surface indicates that the transgranular fracture con- tributes to the higher ductility of sintered Ni-Mn-Ga alloy. In addition, the transformation strain in sintered Ni-Mn-Ga alloy is studied for the first time.展开更多
The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where orde...The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where ordered phase is obtained in the furnace cooled（FC）sample while disordered phase is reserved in the water quenched（WQ）sample.The coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic order.Giant magnetic entropy change（ΔS_（mag））derived from magnetic field induced martensitic transformation is confirmed for both samples,and can be remarkably enhanced by the atomic ordering.The largestΔS_（mag） of 20.9J/（kg·K）is obtained at 307.5Kunder 5Tin the FC sample.展开更多
基金This work is financially supported by the National Natural Science Foundation of China ( No 50531020)
文摘NiMnGaferromagnetic shape memory thin film was deposited onto Al foil using r.f.magnetron sputtering technique.The crystallization behavior of the film was investigated by XRD and DSC.The activation energy of crystallization of the film was calculated by Kissinger’s method.The results show that the crystallization temperature of NiMnGafree-standing thin film in martensite state is 372 ℃,and the activation energy of crystallization is about 191.9 kJ·mol-1.
基金supported by the National Natural Science Foundation of China(Grant Nos.51271065 and 51301054)the Program for New Century Excellent Talents in Heilongjiang Provincial Education Department,China(Grant No.1253-NCET-009)+1 种基金the Youth Academic Backbone in Heilongjiang Provincial Education Department,China(Grant No.1251G022)the Projects of Heilongjiang,China,and China Postdoctoral Science Foundation
文摘A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga alloy, the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe-Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50901026)the Youth Topnotch Inno-vative Talents Program of Harbin University of Science and Technology
文摘The effect of Co content on magnetic property and phase stability of Ni50-xMn25Ga25Cox ferromagnetic shape memory alloys has been investigated using first-principles calculations. The total energy difference between paramagnetic and ferromagnetic state of austenite plays an important role in the magnetic transition. The high Curie temperature can be attributed to the stronger Co-Mn exchange interaction as compared to the Ni-Mn one. The phase stability of Niso-xMn25Ga25Cox austenite increases with increasing Co content, which is discussed based on the electronic structure.
基金Project supported by the National Natural Science Foundation of China (Grant No 50671034)the Natural Science Foundation of Hebei Province,China (Grant No E2008000072)+1 种基金the Research Project of Hebei Provincial Office of Education,China (Grant No 2007306)the Project of Technological Research and Development of Hebei Province,China (Grant Nos 07215137 and 07215134)
文摘The martensitic transformation in Co37Ni34Al29 ribbon is characterized in detail by means of in-situ thermostatic x-ray diffraction and magnetic measurements.The results show a structural transition from the body-centred cubic to martensite with a tetragonal structure during cooling.Comparison between the results of the diffraction intensity with the magnetic susceptibility measurements indicates that the martensitic transformation takes place in several different steps during cooling from 273 to 163 K.During heating from 313 to 873 K,the peak width becomes very wide and the intensity turns very low.The γ-phase （face-centred cubic structure） emerges and increases gradually with temperature increasing from 873 to 1073 K.
基金the National Natural Science Foundation of China (Grant No.50271023) the Natural Science Foundation of Hebei Province (Grant No. 503031).
文摘The influence of stresses on martensitic transformation in Ni50Mn19Fe6Ga25 melt-spun ribbons was studied. X-ray diffraction examination shows that the ribbon has a pure cubic L21 phase at room temperature and that the ribbon surface exhibits [100] preferentially oriented texture, while the [110] axis is about 45° tilted from the normal of the ribbon. By calculating the d spacing at different angles with the length direction of the ribbon, the tension was observed. It was found that the direction of the stress was along [010] direction of the oriented textured grains. During cooling, there is no obvious structural transition observed in as-spun ribbons. However, when the ribbons were annealed at 900 K for 24 h, the tension along [010] direction disappeared and the structural transition from cubic to tetragonal occurred obviously during cooling. It indicates that it is the tension along [010] direction to suppress the martensitic transformation in the as-spun ribbons.
基金Project (1253-NCET-009) supported by Program for New Century Excellent Talents in Heilongjiang Provincial University,ChinaProject (1251G022) supported by Program for Youth Academic Backbone in Heilongjiang Provincial University,ChinaProjects (50901026,51301054) supported by the National Natural Science Foundation of China
文摘The effect of Co substitution on magnetic properties of Ni-Mn-Sn shape memory alloy was revealed by first-principles calculations. Large magnetization difference in Ni-Mn-Sn alloy obtained by addition of Co arises from enhancement of magnetization of austenite due to change of Mn-Mn interaction from anti-ferromagnetism to ferromagnetism. Total energy difference between paramagnetic and ferromagnetic austenite plays an important role in magnetic transition of Ni-Co-Mn-Sn. The altered Mn 3d states due to Co substitution give rise to difference in magnetic properties.
文摘The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （FSMA） composite and hybrid mechanism that can provide a fast response and a strong thrust. The caudal peduncle actuator was inspired by Scomber Scombrus which utilises thunniform mode swimming, which is the most efficient locomotion mode evolved in the aquatic environment, where the thrust is generated by the lift-based method, allowing high cruising speeds to be maintained for a long period of time. The morphology of an average size Scomber Scombrus （length in 310 mm） was investigated, and a 1：1 scale caudal peduncle actuator prototype was modelled and fabricated. The propulsive wave characteristics of the fish at steady speeds were employed as initial design objectives. Some key design parameters are investigated, i.e. aspect ratio （AR） （AR = 3.49）, Reynolds number （Re = 429 649）, reduced frequency （σ = 1.03）, Strouhal number （St = 0.306） and the maximum strain of the bent tail was estimated at ε = 1.11% which is in the range of superelasticity. The experimental test of the actuator was carried out in a water tank. By applying 7 V and 2.5 A, the actuator can reach the tip-to-tip rotational angle of 85° at 4 Hz.
基金Project supported by the New Century Excellent Talents in Heilongjiang Provincial University,China(Grant No.1253-NCET-009)the Youth Academic Backbone in Heilongjiang Provincial University,China(Grant No.1251G022)the National Natural Science Foundation of China(Grant Nos.50901026 and 51301054)
文摘The mechanism for the effects of pressure on the magnetic properties and the martensitic transformation of Ni-Mn- Sn shape memory alloys is revealed by first-principles calculations. It is found that the total energy difference between paramagnetic and ferromagnetic austenite states plays an important role in the magnetic transition of Ni-Mn-Sn under pressure. The pressure increases the relative stability of the martensite with respect to the anstenite, leading to an increase of the martensitic transformation temperature. Moreover, the effects of pressure on the magnetic properties and the martensitic transformation are discussed based on the electronic structure.
基金Project supported by the Chongqing City Funds for Distinguished Young ScientistsChina(Grant No.cstc2014jcyjjq50003)+5 种基金the Basic and Frontier Research Project of Chongqing CityChina(Grant No.cstc2013jj B50001)the Project of Chongqing Normal UniversityChina(Grant No.13XLB030)the Project of Scientific Research for High Level Talent in Colleges and Universities of Hebei ProvinceChina(Grant No.GCC2014042)
文摘The total energy, electronic structures, and magnetisms of the Al Cu2Mn-type Co2TiSb1-xSnx（x = 0, 0.25, 0.5） with the different lattice parameter ratios of c/a are studied by using the first-principles calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, a ferromagnetic shape memory effect can be expected to occur in these alloys. The Al Cu2Mn-type Co2TiSb1-xSnx（x = 0, 0.25, 0.5） alloys are weak ferrimagnets in the austenitic phase and martensitic phase.
基金supported by the National Key Research and Development Program of China(Nos.2022YFE0109500 and 2021YFB3501401)the National Natural Science Foundation of China(Nos.52171190 and 52301250).
文摘The mutual coupling of structure and magnetism is crucial for Heusler alloys.In this paper,Ni_(50)Mn_(34)Sb_(16-x)Ga_(x)(0≤x≤16)alloys were prepared by arc melting.Based on the test results of structure and magnetism,the magnetic-structural phase diagram of Ni_(50)Mn_(34)Sb_(16-x)Ga_(x)(0≤x≤16)was drawn.The structure changes from cubic to monoclinic and finally to tetragonal as the x increases at room temperature.Its phase diagram shows a morphotropic phase boundary(MPB)starting from a tricritical triple point(around the Ni_(50)Mn_(34)Sb_(5)Ga_(11)alloy)of a cubic paramagnetic phase,ferromagnetic monoclinic,and antiferromagnetic tetragonal phases.And Ni_(50)Mn_(34)Sb_(5)Ga_(11)alloy has experienced five different phase states:paramagnetic austenite→ferromagnetic austenite→antiferromagnetic martensite→ferromagnetic martensite→spin glass as the temperature decreased.Further study of the alloys’magnetostrictive properties near the MPB showed that as x increases,a negative strain initially appears,followed by a W-type that crosses negative and positive strains,and then a positive strain.This is caused by the inconsistency in the speed and degree of magnetic domain walls response with monoclinic and tetragonal coexisting structures.This indicates that coupling between structure and magnetism is critical to the properties of materials.This work provides valuable insights into the magnetostrictive behavior and structural evolution of Heusler alloys,particularly in the context of MPB systems,and offers guidance for the design and optimization of material properties through controlled magnetic-structural interactions.Kindly check and confirm the edit made in the title.The edit made in the title has been confirmed to be accurate.
基金financially supported by the National Basic Research Program of China(No.2012CB619404)the National Natural Science Foundations of China(Nos.51221163,51331001)+1 种基金Beijing Natural Science Foundation(No.2132126)the Fundamental Research Funds for Central Universities。
文摘Studies on Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys(FSMAs)have been quite active topics in recent years.Unlike previous reports where the amount of Co doping was generally less than 8 at%,in this work Ni_(55-x)Co_(x)Mn_(20)Ga_(25)(8.5≤x≤11.0)alloys were studied with high Co doping.Unusual effects of both composition and magnetic field on phase transitions were observed.With the increase in substitution of Co for Ni,the magnetic transition temperatures increase gradually but the martensitic transformation temperature decreases quite sharply.In particular,the average decrease in the martensitic transformation temperatures is up to 100 K which is nearly twice that in the case of Co content of less than 8 at%.Further,under an applied magnetic field ranging from 0.03 to 0.60 T,abnormal stabilization of a martensite phase with lower magnetization was monitored.Magnetic entropy change of 1.6 J·kg^(−1)·K^(−1)was induced at the martensitic transformation of Ni46.5Co8.5Mn20Ga25 alloy by an applied field of 1 T.The magnetic contributions,including the magnetocrystalline anisotropy and the Zeeman energy,to the thermodynamics of the martensitic transformation are considered to understand the observed unusual phenomena.This work results in new insights into the understanding of Co-doped Ni–Mn-based ferromagnetic shape memory alloys.
基金financially supported by the National Basic Research Program of China (No. 2012CB619404)the National Natural Science Foundation of China (Nos. 50925101, 51221163, and 51001004)+1 种基金Beijing Natural Science Foundation(No. 2132026)the Fundamental Research Funds for Central Universities (No. YWF-12-LZGF-052)
文摘Ni30Cu20Mn37＋xGa13-x（x = 0–4.5） alloys were studied with the phase transformation and mechanical properties. With the increase of Mn content, the martensitic transformation temperatures increase and the Curie temperature decreases. Simultaneously, the room temperature microstructure evolves from single phase of austenite to dual phases containing martensite and precipitation. Both the ductility and the strength of the polycrystalline alloys are significantly improved by the precipitation. Coupled magnetostructural transition from weak magnetic martensite to ferromagnetic austenite is obtained in both single-phase and ductile dual-phase alloys.
基金supported by the National Natural Science Foundation of China (Grant No. 10976007)the Fundamental Research Funds for the Central Universities (Grant Nos. ZYGX2009J046 and ZYGX2009X007)Royal Academy of Engineering-Research Exchanges with China and India Awards in UK
文摘This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry （DSC） methods. The structure type of Ni55.5Fe18Ga26.5-xSix alloys is determined by x-ray diffraction （XRD）, and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite （with Si content x = 0） to body-centred cubic austenite （with x = 2） at room temperature. The martensitic transformation temperatures of the Ni55.sFelsGa26.5-xSi~ alloys decrease almost linearly with increasing Si content in the Si content range of x _~ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga^Si alloy. The valence electronic concentrations, size factor, L21 degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.
基金Funded by the Foundation for Department of Science and Technology of Jiangxi Province (No.ZDG03800)the Foundation for Department of Education of Jiangxi Province(No.GJJ11579)
文摘A series of Ni-Fe-Ga alloys near the prototype Heusler composition （X2YZ） were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and annealing treatment were studied in detail by an optical microscope, X-ray diffraction, and differential scanning calorimeters methods. The experimental results show that the martensitic transformation temperatures increase almost linearly with increasing Ni content in all the NiFeGa alloys. Annealing the Ni55.5Fe18Ga26.5 alloy at 100-500 ℃ for 3 h and at 300 ℃ for 1-10 h shifts the martensitic transformation start temperature by almost 20 ℃ to high temperature. The variations in the martensitic transformation temperatures in these alloys are discussed in terms of structural differences resulting from alloy composition and annealing treatment.
基金supported by the National Natural Science Foundation of China (Grant No. 50971052)the Scientific Research Fund of Heilongjiang Provincial Education Department of China (Grant No. 11531059)
文摘The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed sintered specimens exhibit typical martensitic transformation behaviours. The martensite of the sintered specimen after annealing exhibits a ferromagnetic nature. Moreover, study of the fracture surface indicates that the transgranular fracture con- tributes to the higher ductility of sintered Ni-Mn-Ga alloy. In addition, the transformation strain in sintered Ni-Mn-Ga alloy is studied for the first time.
基金supported by the National Natural Science Foundations of China(Grant Nos.51331001, 51520105002,51601008,and 51601007)the Fundamental Research Funds for Central Universities
文摘The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where ordered phase is obtained in the furnace cooled（FC）sample while disordered phase is reserved in the water quenched（WQ）sample.The coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic order.Giant magnetic entropy change（ΔS_（mag））derived from magnetic field induced martensitic transformation is confirmed for both samples,and can be remarkably enhanced by the atomic ordering.The largestΔS_（mag） of 20.9J/（kg·K）is obtained at 307.5Kunder 5Tin the FC sample.
