Atomic scale simulation of the strain rate and temperature dependence of crack growth and stacking faults in zirconium

Abstract

Molecular dynamics simulations of single crystal zirconium fracture were performed to study the deformation mechanisms active on the basal and prismatic planes. The effects of temperature (0 to 300 K) and strain rate (108–1010 s −1 ) were investigated. Crack tip orientation was found to strongly affect the fracture behaviour. On the basal plane twinning ({11¯21}<1¯126>) and emission of <c + a> type dislocations that then dissociated into partial dislocations around pyramidal I2 stacking faults were seen to occur during fracture. At higher strain rates (109 and 1010 s −1 ), twinning occurred. The emission of edge dislocations ( 1 3 <1¯210> type) was prevalent on the prismatic plane and were found to be strongly affected by temperature. At higher temperature (150 and 300 K), the dislocation density increased. The crack grew further at 150–300 K than at 0 K and the shielding effect of dislocations was limited due to their movement away from the crack tip. The addition of iodine at basal I2, pyramidal I1 and I2 stacking faults was seen to decrease the energy of its formation whereas for the prismatic stacking fault it was found to increase it. The iodine also changed the order of favourability of the stacking faults with basal I2 and pyramidal I1 stacking faults becoming much more favourable and prismatic going from most to least favourable.