Revealing essence of magnetostructural coupling of Ni-Co-Mn-Ti alloys by first-principles calculations and experimental verification

• Published in: Rare metals 2022-06, Vol.41 (6), p.1933-1947
• Main Authors: Guan, Zi-Qi, Bai, Jing, Zhang, Yu, Gu, Jiang-Long, Jiang, Xin-Jun, Liang, Xin-Zeng, Huang, Run-Kai, Zhang, Yu-Dong, Esling, Claude, Zhao, Xiang, Zuo, Liang
• Format: Article
• Language: English
• Subjects: Alloys; Biomaterials; Chemistry and Materials Science; Coupling; Energy; First principles; Fracture strength; Free energy; Heat of formation; Heusler alloys; Magnetic properties; Manganese; Martensite; Martensitic transformations; Materials Engineering; Materials Science; Mathematical analysis; Mechanical properties; Metallic Materials; Nanoscale Science and Technology; Nickel; Original Article; Physical Chemistry; Room temperature; Titanium base alloys; Verification
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-021-01947-2

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-principles calculations and experimental verification. The calculation 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 transformation 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 (Δ M ) and magnetic entropy changes (Δ S 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 magnetocaloric effect but also has excellent mechanical properties. In addition, the 6 M modulated martensite is evidenced in the Ni-Co-Mn-Ti alloys via transmission electron microscopy technique. Graphical abstract