The effect of dislocation distribution in the boundaries of an arrested twin on the nucleation of micro-cracks at its tip was investigated. The twin was simulated by a double step pileup (cluster) of twinning dislocations located in adjacent slip planes. The equilibrium equations for dislocations were solved numerically. Clusters with different total numbers of dislocations and with different ratios of the numbers of dislocations at the upper and lower twin boundaries were considered. The formation of micro-cracks as a result of coalescence of head dislocations according to the force and thermally activated mechanisms was analyzed. The equilibrium configurations of a single twin boundary and of the twin were calculated. It was found that the condition for micro-crack formation at the twin tip considerably depended upon the ratio of the numbers of dislocations in twin boundaries. In the limit, this condition coincides with the condition of crack formation at the tip of a single twin boundary with the same total number of dislocations. It was shown that thermally activated formation of a micro-crack corresponds to lower values of the critical stress.

Effect of Dislocation Distribution in Twin Boundaries on the Nucleation of Microcracks at the Twin Tip. V.A.Fedorov, V.A.Kuranova, Y.I.Tyalin, S.N.Pluzhnikov: Physics of the Solid State, 2002, 44[6], 1102-5