Correlation of mechanical anisotropy with fine grain strengthening for Sm2Co17-type sintered permanent magnets

Abstract

The as-solution-treated Sm2Co17-type magnets exhibiting a single 1:7H phase with different average grain sizes (D) were designed. Anisotropy of bending strength (Rbb) and compressive strength (Rmc) of the magnets were investigated. Moreover, the Rbb increases from 86 to 173 MPa with D decreasing from ∼52 to ∼18 μm for group c//h samples. The Hall–Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets, giving deep understanding of the mechanical anisotropy characteristics. The relatively high Hall–Petch coefficient KRbb (0.79 MPa⋅m1/2) gives rise to the largest Rbb (173 MPa) for group c//h samples. The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features (grain boundaries). Grain refinement is an effective way to enhance the mechanical properties of Sm2Co17-type sintered magnets.