Fracture toughness of low porosity Dy123 bulks melt-processed in pure oxygen

Fracture toughness evaluations of specimens cut from low porosity Dy123 single-grain bulks melt-processed in pure oxygen were carried out at room temperature. While the porosity of a conventional Dy123 single-grain bulk melt-processed in air measured in the previous study is about 20%, those of the Dy123 bulks melt-processed in pure oxygen are below 4%. The minimum of the fracture toughness values of the low porosity bulk is 15% higher than that of the conventional bulk, and the maximum of the former and that of the latter are close to each other. The difference in the fracture toughness among these bulks is discussed in association with the porosity and the mechanical properties of the matrix evaluated by Vickers indentation tests