Role of Ni and Co in tailoring magnetic and mechanical properties of Fe84Si2B13P1 metallic glass

Abstract

The disastrous annealing embrittlement of Fe-based metallic glasses with excellent soft magnetic properties is a long-standing issue. In order to alleviate the annealing embrittlement without worsening the soft magnetic properties, ferromagnetic elements Co and Ni are introduced to the Fe84Si2B13P1 metallic glasses. The microstructure, mechanical and magnetic properties are investigated by synchrotron diffraction, two-point bending test and magnetometry. It is found that, in contrast to Co, proper Ni substitution for Fe significantly optimizes the Hc of Fe84Si2B13P1 metallic glasses and keeps the Bs at a high level. According to bending tests, the ductile-brittle transition temperature of the metallic glasses increases slightly with Ni substitution and decreases prominently with Co substitution. Ultimately, the ductile Fe82Ni2Si2B13P1 metallic glasses with Bs of 1.65 T and Hc of 3.4 A/m have been successfully obtained. Macroscopically, the cheerful propensity to form well-distributed shear bands during bending of Ni-substituted annealed alloys contributes to their good ductility. Furthermore, the alteration of ductile-brittle transition temperature can be conducted by the structural change at the medium-range scale as revealed by the pair distribution function measurements. After annealing the compression at atomic scale ranging from 6 Å to 16 Å of Co-substituted metallic glasses may hinder the creation of well-distributed shear bands and give rise to the deterioration of bending ductility. This work provides a perspective to understand the ductile-brittle transition of metallic glasses from the atomic scale.