Distribution of Mechanical Properties in a Single-Grain Sm123 Bulk Superconductor at Liquid Nitrogen Temperature

摘要

To investigate the mechanical properties of a single-grain Sm123 bulk superconductor with 10 wt% Ag at liquid nitrogen temperature, 3-point bending tests by monotonic and repeated c-axis loadings on specimens cut from the bulk were carried out. Monotonic loading tests revealed that the Young's modulus and the bending strength scatter from 66 to 149 GPa and 38 to 107 MPa, respectively. The maximum strength in the vicinity of the seed was equal to that of Y123 without Ag and slightly lower than that of Gd123 with 10 wt% Ag. On the other hand, the minimum strength obtained in the region remote from the seed was significantly lower than those of the other bulks. From observations on the fracture surfaces of the specimen with the minimum strength, densely gathered large pores were found in the surface region. The fracture stress for repeated loadings up to$5times 10^4 cycles$ranged from 70 to 90 MPa; the fatigue endurance limit for the numbering cycles was estimated to be 60 MPa.