Effect of Dy211 content on fracture toughness of Dy123 bulks

To evaluate the fracture toughness of Dy123 with X mol% Dy211 (X = 15, 20 and 25) bulks, bending tests on V-notched specimens were carried out at room temperature. The average value of the fracture toughness for X = 25, 1.47 MPa m1/2, was higher than those for X = 15 and 20, 1.24 and 1.17 MPa m1/2, respectively. The porosity of specimens cut from the top region for X = 25 was extraordinarily low and the fracture toughness was high. According to the relation between the fracture toughness and the porosity, the fracture toughness of the material of no pore was estimated to be 1.75 MPa m1/2.