473 Kで変形したマグネシウム多結晶における粒界付近の組織

Abstract

Polycrystalline specimens of magnesium have been deformed in tension at 473 K, and the behaviors of grain boundary deformation were investigated mainly by optical microscopy. Particular attension has been paid to the formation of a band region of grain boundary, which is a cell region formed by the localized grain boundary migration (i.e. bulging mechanism) and the polygonization in a region adjacent to the grain boundary. Results obtained are summarized as follows.(1) The specimens had a strong preferred orientation with the basal planes lying parallel to the tensile direction (rolling direction), therefore the Schmid factor for basal slip is small. At 473 K, however, basal slips have been activated in consequence of the relative difficulty in occurrence of non-basal slip and twinning.(2) When the orientation relationship between adjoining grains is chosen in such a way that the crystal rotation due to basal slips is opposed to each other, the band region of grain boundary forms preferentially.(3) Therefore, these results indicate that the additional stress concentration at grain boundary induced by deformation of grains is a dominating factor in the formation of the band region.