Effect of ordered domains on the fracture toughness of high Co-Ni secondary hardening steel

The mechanism on the sharp decrease in fracture toughness of the overaged high Co-Ni secondary hardening steel has been investigated. Experimental results showed that ordering process occurred and ordered domains were formed in the steel after overaging. The ordered domains will impede the movement of the dislocations and act as local brittle centers during deformation, which leads to the sharp decrease in the fracture toughness of the steel. Based on the effect of the reverted austenite films and ordered domains, a model was proposed to explain the behavior of the fracture toughness of the steel.