The influence of grain size on fracture toughness in metals

Abstract

We perform computer modelling of the dislocation emission from the crack tip under the variable external stress in molibdenum. The following material properties are obtained: the number of dislocations in a grain, the energy of dislocation movement and fracture toughness. It is showm that the fracture toughness depends slightly on the grain size when the size is less than 50 µm and is constant when it is larger. This is because at this value of the grain size the plastic zone ceases to touch the grain boundary. The number of the dislocations in a grain and the dislocation ensemble movement energy grow rapidly with the grain size when the size is less than 50 µm and are constant when the grain size is larger.