4491734 X-ray detector and method of making same : Keik Yamaguchi, Kazuyuk Tomarikawa, Haruo Kurochi, Jiro Namikawa, Shigeru Matsumura, Ryo Takahashi, Shiro Mori, Tokyo, Japan assigned to Yokogawa Hokushin Electric Corporation

Abstract

Sm-Co permanent magnets are usually very brittle which makes them vulnerable to even mild impacts. Recently, it was 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). In addition, the mechanical properties of the two-phase composites with an interface should be 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 SmCo5 and Sm2Co17 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 the amorphous shear band is initiated in the Sm2Co17 phase, the sample quickly necks toward 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.