Mechanical Properties of Samarium Cobalt: A Molecular Dynamics Study

Abstract

Sm-Co permanent magnets are usually very brittle which makes them vulnerable to even mild impacts. Recently, it is reported by simulation and confirmed by experiment that SmCo₅ can be plastically deformed via amorphous shear bands activated by external stress Since most Sm-Co magnets mainly consist of the Sm₂Co₁₇ phase, it is necessary to study how the Sm₂Co₁₇ phase can be deformed compared with the SmCo₅ phase (existing also in Sm-Co magnets). Specially, the mechanical properties of the two-phase composites with an interface are investigated. In this paper, we show that the Sm₂Co₁₇ phase can also be plastically deformed under tensile loading due to the formation of amorphous shear bands. We find that the interfacial stress between the SmCo₅ and SmSm₂Co₁₇ significantly affects the formation of amorphous shear bands. The formation energies of amorphous shear bands are lower than the energies needed for transgranular, intergranular and interphase cleavage. The two-phase samples notched at the interface are also deformed by tensile loading. When amorphous shear band is initiated in the SmSm₂Co₁₇ phase the sample quickly necks before failure. In contrast, when amorphous shear band is initiated in the SmCo₅ phase the sample can accommodate more strain. These results help us understand the intrinsic mechanical properties of Sm-Co magnets.

Keywords: Sm-Co, Plasticity, shear band, Amorphization