Migration of specific planar grain boundaries in bicrystals: application of magnetic fields and mechanical stresses

Abstract

Recent research on the dynamics of planar grain boundaries is reviewed. Novel measuring techniques developed for in situ observation and recording of magnetically and stress driven grain boundary migration are presented. The results of migration measurements obtained on bismuth, zinc and aluminum bicrystals are addressed. The experiments revealed that the inclination of a 〈112〉 tilt boundary in Bi has a very strong influence on its mobility. The migration of planar tilt grain boundaries with different misorientation angles was measured in situ in bicrystals of high purity zinc. The results proved that there is a pronounced misorientation dependence of grain boundary mobility in the investigated angular range. The shear stress induced migration of planar symmetric 〈100〉 tilt boundaries in aluminum bicrystals was observed to be accompanied by a lateral translation of the adjacent grains. The coupling between boundary motion and shearing is not confined to low angle and some low Σ high angle boundaries, but occurs also for non-coincidence high angle 〈100〉 tilt boundaries. It has been found that also for stress induced grain boundary motion there is a misorientation dependence of the migration activation parameters. Lower values of the activation enthalpy and the pre-exponential mobility factor can be associated with boundaries with tilt angles close to low Σ CSL orientation relationships.

Keywords

grain boundary / migration / magnetic driving force / stress / shear strain