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Phase transition of Ni_(55-x)Co_(x)Mn_(20)Ga_(25)(8.5≤x≤11.0)alloys with different compositions and magnetic fields

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Rare Metals 2023年第2期42卷 572-578页

作者： Xiao wang jing-min wang Hui Hua Cheng-Bao Jiang Key Laboratory of Aerospace Materials and Performance(ministry of Education) School of Materials Science and EngineeringBeihang UniversityBeijing100191China

Studies on Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys(FSMAs)have been quite active topics in recent *** 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 *** effects of both composition and magnetic field on phase transitions were *** the increase in substitution of Co for Ni,the magnetic transition temperatures increase gradually but the martensitic transformation temperature decreases quite *** 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 *** 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 *** magnetic contributions,including the magnetocrystalline anisotropy and the Zeeman energy,to the thermodynamics of the martensitic transformation are considered to understand the observed unusual *** work results in new insights into the understanding of Co-doped Ni–Mn-based ferromagnetic shape memory alloys.

关键词： Ni-Mn-Ga Ferromagnetic shape memory alloys Martensitic transformation Magnetic properties Magnetocaloric effect

Topological Insulators on the Ruby Lattice with Rashba Spin-Orbit Coupling

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Communications in Theoretical Physics 2013年第7期60卷 129-135页

作者： HOU jing-min wang Guo-Xiang Department of Physics Southeast University Nanjing 211189 China

We investigate a tight-binding model of the ruby lattice with Rashba spin-orbit coupling. We calculate the band structure of the lattice and evaluate the Z2 topological indices. According to the Z2 topological indices and the band structure, we present the phase diagrams of the lattice with different filling fractions. We findthat topological insulators occur in some range of parameters at 1/6, 1/3, 1/2, 2/3 and 5/6 filling fractions. We analyze and discuss the characteristics of these topological insulators and their edge states.

关键词： topological insulators ruby lattice rashba spin-coupling

A linear elastic Ni_(50)Mn_(25)Ga_9Cu_(16) martensitic alloy

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Rare Metals 2013年第1期32卷 29-32页

作者： Cong-Wei wang jing-min wang Cheng-Bao Jiang Key Laboratory of Aerospace Materials and Performance (ministry of Education) School of Materials Science and Engineering Beiing University of Aeronautics and Astronautics

The linear elasticity was studied in a martens- tic alloy NisoMn25Ga9Cu16. A 0.4 % linear elastic strain is btained in the polycrystalline sample under compressive stress of 745 MPa. The elastic modulus is 186 GPa. The obtained linear elastic strain and elastic modulus are much higher than that of ternary Ni-Mn-Ga martensitic alloys.~.bstract The linear elasticity was studied in a martens- tic alloy NisoMn25Ga9Cu16. A 0.4 % linear elastic strain is ~btained in the polycrystalline sample under compressive stress of 745 MPa. The elastic modulus is 186 GPa. The obtained linear elastic strain and elastic modulus are much higher than that of ternary Ni-Mn-Ga martensitic alloys.

关键词： Ni-Mn-Ga Linear elasticity Elasticmodulus Martensite

Microstructure,orientation and magnetostrictive properties of Fe_(81)Ga_(19) polycrystal grown with Bridgman method

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Rare Metals 2023年第12期42卷 4184-4188页

作者： Sen-Kuan Meng Yi-Jun Chen jing-min wang Key Laboratory of Aerospace Materials and Performance(ministry of Education) School of Materials Science and EngineeringBeihang UniversityBeijing 100191China

The microstructure,orientation and magnetostrictive properties of a Fe_(81)Ga_(19)poly crystal grown by Bridgman method were investigated.A big central single crystal surrounded by some small crystals was *** X-ray back-reflection confirmed theorientation of the central crystal and deviation from thedirection for the edge *** boundaries were monitored in the *** was confirmed that orientations of all the subgrains were very close to the*** of the magnetostriction in different crystals indicated the strong anisotropy of the magnetostrictive *** work opens the possibility of preparing large-sized single crystal of FeGa alloys by using the Bridgman method.

关键词： FeGa Magnetostriction Crystal growth

Phase transition and mechanical properties of Ni_(30)Cu_(20)Mn_(37+x)Ga_(13-x)(x=0–4.5) alloys

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Rare Metals 2014年第5期33卷 547-551页

作者： Huan-Fang wang jing-min wang Cheng-Bao Jiang Hui-Bin Xu School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics

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.

关键词： Ferromagnetic shape memory alloys(FSMAs) Martensitic transformation Magnetostructural transition Mechanical properties

Shape memory effect of dual-phase NiMnGaTb ferromagnetic shape memory alloys

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Journal of Iron and Steel Research International 2019年第3期26卷 321-328页

作者： Jiang Zhang Yong-hong Ma Ruo-lin Wu jing-min wang Institute of Higher Education Beihang UniversityBeijing 100191China School of Materials Science and Engineering Beihang UniversityBeijing 100191China Central Iron&Steel Research Institute Beijing 100081China

The evolution of microstructure,reverse martensitic transformation and the conelated influence on shape memory effect was investigated in as-cast and directionally solidified dual-phase NiMnGaTb *** directionally solidified alloys exhibit single-crystal microstructure,preferred dendrite microstructure,and mussy dendrite microstructure in the specimens grown at a withdrawal rate(v)of 10,50 and 200,and 1000μm/s,*** precipitates dispersively distribute in the martensite matrix for the directionally solidified *** the refined grains and particle precipitates,the reverse martensitic transformation gradually shifts to lower temperatures and the temperature span is significantly *** directional solidification technology can effectively enhance the strains recovered due to shape memory effect C;sme)and decrease the compressive stress required to trigger the reorientation of twins(δ)via the realization of preferred orientation,while the maximalεsme and minimumδcan reach 4.96%and 14 MPa in v=10μm/s specimens,*** formation of dendrite morphology degrades the shape memory strain,andεsme decreases with the growth of secondary dendritic arms.

关键词： NiMnGaTb alloy Directional solidification Dual-phase microstructure Shape memory effect

Influence of cooling rate on magneto-structural transition and magnetocaloric effect of Ni_(30)Cu)8Co_(12)Mn_(37)Ga_(13) alloy

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Journal of Iron and Steel Research International 2017年第7期24卷 711-717页

作者： Zhu-jun Jiang Yu-ye Wu jing-min wang Cheng-bao Jiang School of Materials Science and Engineering Beihang University School of Physics and Nuclear Energy Engineering Beihang University

The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically *** 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）*** coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic *** 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 *** largestΔS_（mag） of 20.9J/（kg·K）is obtained at 307.5Kunder 5Tin the FC sample.

关键词： Ferromagnetic shape memory alloy Heat treatment Martensitic transformation Magnetocaloric effect Cooling rate Magneto-structural transition

Temperature stability of SmCo(2:17) magnets modified by Ni-Cr two-layer coating

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Rare Metals 2019年第3期38卷 238-244页

作者： Saira Bibi jing-min wang M. Faisal Rathore Cheng-Bao Jiang School of Materials Science and Engineering Beihang University National Center of Physics Quaid-e-Azam University

The oxidation resistance behavior of SmCo(2:17)-type high-temperature magnets modified with Ni-Cr two-layer coating was studied. The study depicts the mass gain kinetics and magnetic properties of uncoated and NiCr-modified magnets oxidized at high temperature(500 ℃) in air for 200 h. The oxidation test results illustrate that the mass gain of uncoated magnet is6.95 mg·cm^(-2) which is more than that(0.08 mg·cm^(-2)) of coated magnet after 200 h. For the magnetic properties concerned, there is a great loss for uncoated magnet, while for coated magnet, magnetic properties do not change much. The study of uncoated magnet through X-ray diffraction(XRD) and electron probe microanalysis(EPMA) shows that the invasion of oxygen at high temperature leads to the loss of magnetic properties by changing the microstructure of magnet.

关键词： SmCo(2:17) magnets Surface modification High temperature stability Ni-Cr coating

Hot corrosion of surface-modified Sm_(2)Co_(17) high-temperature magnet with Ni and Ni/Cr bilayer coatings in 75 wt% Na_(2)SO_(4)–NaCl mixture

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Rare Metals 2021年第9期40卷 2494-2500页

作者： Saira Bibi jing-min wang Tariq Mehmood Waheed Qamar Khan Cheng-Bao Jiang Key Laboratory of Aerospace Materials and Performance(ministry of Education) School of Materials Science and EngineeringBeihang UniversityBeijing 100191China Institute of Advanced Materials Bahauddin Zakariya UniversityMultan 60800Pakistan School of Space and Environment Beihang UniversityBeijing 100191China

Hot corrosion behavior of Sm_(2)(Co, Fe, Cu,Zr)17-type high-temperature magnetic alloy without and with a protective coating of Ni and Ni/Cr bilayer at 500 ℃ in a corrosive mixture of 75 wt% Na_(2)SO_(4)–NaCl for 100 h was reported in this paper. The obtained results of timedependent weight change established the parabolic growth of oxidized surface of bare magnets(8.87 mg·cm^(-2)),which caused a rapid loss of magnetic properties measured both at room and high temperatures(500 ℃). X-ray diffraction(XRD) analysis revealed the growth of oxides for bare magnet and Cr–oxides(Cr_(2) O_(3)), top layer of Ni/Cr bilayer coating, but in the case of single coating, Ni–sulfides formation indicated penetration of sulfur, which is further verified by electron probe microanalysis with energy dispersive spectroscopy(EPMA/EDS) *** showed that bilayer-coated samples(Ni/Cr) performed better than Ni-coated and bare samples.

关键词： Hot corrosion SmCo-based alloys Oxidation Coatings