J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (3): 396-401.DOI: 10.1016/j.jmst.2018.09.032

• Research Article • Previous Articles     Next Articles

Resolution of a discrepancy of magnetic mechanism for Elinvar anomaly in Fe-Ni based alloys

Fangyu Qina, Wenlong Xiaoa, Fengshuang Lub, Yuanchao Jic, Xinqing Zhaoa*(), Xiaobing Renc   

  1. aSchool of Materials Science and Engineering, Beihang University, Beijing 100191, China
    bFunctional Materials Research Institute, Central Iron and Steel Research Institute, Beijing 100081, China
    cMulti-Disciplinary Materials Research Center, Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an, 710049, China;
  • Received:2018-07-21 Revised:2018-08-17 Accepted:2018-08-30 Online:2019-03-15 Published:2019-01-18
  • Contact: Zhao Xinqing
  • About author:

    1 These authors contributed equally to this work.

Abstract:

Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found, challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains’ formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.

Key words: Fe-Ni based alloys, Elastic modulus, Magnetism, Strain glass transition, Nanodomains