Effects of solute and vacancy segregation on antiphase boundary migration in stoichiometric and Al-rich Fe3Al: A phase-field simulation study

Abstract Effects of segregation of solute atoms and vacancies on migration of antiphase boundaries (APBs) in stoichiometric (Fe-25 at%Al) and Al-rich (Fe-28 at%Al) Fe 3 Al at 673 K have been studied using a phase-field method in which local vacancy concentration is taken into account [Koizumi Y, Allen SM, Minamino Y. Acta Mater 2008;56:5861, ibid . 2009;57:3039]. Boundary mobility ( M ) of APBs having different phase-shift vectors of a/4 and a/2 (hereafter denoted as B 2-APB and D 0 3 -APB, respectively) was evaluated by measuring the boundary velocity of shrinking circular APBs. Similar effects of the segregation on the migration of B 2-APBs were observed in both compositions. Vacancies segregated and Al-atoms were depleted at B 2-APBs in both compositions. Vacancy concentration at B 2-APBs was up to 80% higher than that in the bulk. As a result, the migration of B 2-APBs was greatly enhanced by the vacancy segregation. In contrast, the segregation to D 0 3 -APBs showed a marked composition dependence. Vacancies were depleted and Al-atoms segregated at D 0 3 -APBs in the Al-rich Fe 3 Al, whereas vacancies segregated and Al-atoms were depleted at D 0 3 -APB in the stoichiometric Fe 3 Al. The Al segregation in the Al-rich Fe 3 Al decreased M of D 0 3 -APBs much more significantly than the Al-depletion in the stoichiometric Fe 3 Al. As the APDs shrank, D 0 3 -APBs broke away from the segregation atmospheres and the M increased rapidly in both compositions. A greater increase in the M due to the breakaway was observed in the Al-rich Fe 3 Al than in Fe 3 Al with the stoichiometric composition.