In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples c...In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples calculations and experimental verification.The cal-culation result indicates that the doped Co atoms prefer to occupy the Ni sublattice.The Co atoms tend to flock together in terms of the lowest energy principle.Since the formation energy of the austenite is higher than that of the martensite,the alloys will undergo martensitic transfor-mation for the Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys(x=0-12.5).The magnetostructural coupling point of Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys is predicted in the vicinity of x=11-12.Based on the computational composition Ni_(37.5)Co_(12.5)Mn_(37.5)Ti_(12.5),the Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy with magnetostructural coupling near room temperature was experimentally developed by simultaneously increasing the Ti and Co contents.The largest magnetization change(ΔM)and magnetic entropy changes(ΔS_(m))obtained under magnetic field of 5 T for the martensitic transformation in the Ni_(36)Co_(14)Mn_(36)Ti_(14) alloy are about 87.6 A·m^(2)·kg^(-1)and 21 J·kg^(-1)·K^(-1),respectively.The fracture strength and strain for non-textured polycrystalline Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy reach 953 MPa and 12.3%,respectively.The results show that the alloy not only possesses a large magne-tocaloric effect but also has excellent mechanical proper-ties.In addition,the 6 M modulated martensite is evidenced in the Ni-Co-Mn-Ti alloys via transmission electron microscopy technique.展开更多
The relationship between microstructure and mechanical properties of Ti-Mo microalloyed steels composed of ferrite and bainite with nanometer-sized carbides and isothermally transformed at different temperatures and t...The relationship between microstructure and mechanical properties of Ti-Mo microalloyed steels composed of ferrite and bainite with nanometer-sized carbides and isothermally transformed at different temperatures and time was systematically investigated by tensile test, hardness test, and transmission electron microscopy. Ferrite formed at high temperatures exhibited both planar/curved sheet-like dispersions of interphase precipitates and random dispersion precipitates, with the interphase precipitates being the dominant morphology. In contrast, bainite formed at low temperatures exhibited only random dispersion precipitates. Furthermore, random dispersion precipitates and interphase precipitates were observed within the same ferrite grains. The mechanical properties of the ferrite specimen were superior to those of the bainite specimen. The stress-strain curves of both specimens indicated continuous yielding, high strength, and sufficient tensile elongation. The strengthening of the ferrite specimen was attributed to grain size strengthening, dislocation strengthening, and precipitation hardening, and the degree of precipitation strengthening was approximately 300 MPa.展开更多
基金financially supported by the National Natural Science Foundation of China (No.51771044)the Natural Science Foundation of Hebei Province (No.E2019501061)+2 种基金the Fundamental Research Funds for the Central Universities (No. N2023027)Program of Introducing Talents of Discipline Innovation to Universities 2.0 (No.BP0719037)LiaoNing Revitalization Talents Program (No.XLYC1802023)
文摘In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples calculations and experimental verification.The cal-culation result indicates that the doped Co atoms prefer to occupy the Ni sublattice.The Co atoms tend to flock together in terms of the lowest energy principle.Since the formation energy of the austenite is higher than that of the martensite,the alloys will undergo martensitic transfor-mation for the Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys(x=0-12.5).The magnetostructural coupling point of Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys is predicted in the vicinity of x=11-12.Based on the computational composition Ni_(37.5)Co_(12.5)Mn_(37.5)Ti_(12.5),the Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy with magnetostructural coupling near room temperature was experimentally developed by simultaneously increasing the Ti and Co contents.The largest magnetization change(ΔM)and magnetic entropy changes(ΔS_(m))obtained under magnetic field of 5 T for the martensitic transformation in the Ni_(36)Co_(14)Mn_(36)Ti_(14) alloy are about 87.6 A·m^(2)·kg^(-1)and 21 J·kg^(-1)·K^(-1),respectively.The fracture strength and strain for non-textured polycrystalline Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy reach 953 MPa and 12.3%,respectively.The results show that the alloy not only possesses a large magne-tocaloric effect but also has excellent mechanical proper-ties.In addition,the 6 M modulated martensite is evidenced in the Ni-Co-Mn-Ti alloys via transmission electron microscopy technique.
基金The authors gratefully appreciate the financial support by National Natural Science Foundation of China (51674079)China Postdoctoral Science Foundation (2016M600211).
文摘The relationship between microstructure and mechanical properties of Ti-Mo microalloyed steels composed of ferrite and bainite with nanometer-sized carbides and isothermally transformed at different temperatures and time was systematically investigated by tensile test, hardness test, and transmission electron microscopy. Ferrite formed at high temperatures exhibited both planar/curved sheet-like dispersions of interphase precipitates and random dispersion precipitates, with the interphase precipitates being the dominant morphology. In contrast, bainite formed at low temperatures exhibited only random dispersion precipitates. Furthermore, random dispersion precipitates and interphase precipitates were observed within the same ferrite grains. The mechanical properties of the ferrite specimen were superior to those of the bainite specimen. The stress-strain curves of both specimens indicated continuous yielding, high strength, and sufficient tensile elongation. The strengthening of the ferrite specimen was attributed to grain size strengthening, dislocation strengthening, and precipitation hardening, and the degree of precipitation strengthening was approximately 300 MPa.