Dynamic Fracture Toughness of High-Strength 5KhN3МА Steel

High-strength martensitic–austenitic 5KhN3MA steel is subjected to static and impact bending tests. The crack initiation and propagation energies, the dynamic fracture toughness, the critical ductile–brittle transition temperature, and the fracture microrelief parameters are estimated. The influence of a preliminary shock-wave action on the strength and the dynamic fracture toughness of the steel is studied. The high-rate shock-wave action is shown to increase the fracture toughness of the steel and to shift the brittleness threshold toward lower temperatures. The estimation of acoustic emission characteristics during static bending tests shows that a preliminary dynamic action significantly decreases the total number and the accumulation rate of acoustic emission signals considerably and shifts the final stage of fracture toward large deformation.