Low-temperature embrittlement and fracture of metals with different crystal lattices - Dislocation mechanisms

The state of a low-temperature embrittlement (cold brittleness) and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals) with various crystal lattices (BCC, FCC, HCP) are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength) as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation) and after a low-temperature damaging (neutron) irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron) irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed) due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.