Effects of Ag particle and pore distributions on fracture toughness of Dy123 bulks

Fracture toughness evaluations on Dy123 single-grain bulks with X wt.% Ag (X=5, 7.5 and 10) melt-processed in air were carried out at room temperature, and the scattering of the fracture toughness values is discussed in terms of the distributions of pore and Ag particle in these bulks. The fracture toughness is improved by the Ag addition; the average values are 1.34, 1.44 and 1.54 MPa m1/2 for X=5, 7.5 and 10, respectively. The porosity near the top surface of these bulks is distinctly low. In X=5, an increase of the fracture toughness value with decrease of the porosity is clearly observed. According to the extrapolation of data, it is deduced that the fracture toughness value at 0 % porosity will be 20 % higher than the average value