Dislocation Activity in AZ31B Magnesium Deformed at Moderately Elevated Temperatures via EBSD

摘要

Activation of type slip in wrought magnesium has typicallybeen associated with forming temperatures of 200°C or higher,while contraction twinning has been observed to be moreprevalent at lower temperatures. A recent investigation showedthat when AZ31B sheets with strong basal texture were formed inbiaxial or plane strain tension at room temperature, contractiontwins were observed in banded structures. These bandedstructures disappeared at moderate forming temperatures of 75°Cand 125°C. The hypothesis is that type slip wassufficiently activated at the moderate forming temperatures thatthinning of the sheet was accommodated less by twinning andmore by slip. This paper uses mesoscale electron backscatterdiffraction continuum dislocation microscopy in an SEM todetermine type geometrically necessary dislocationdensity. Preliminary results suggest that the relative amount of geometrically necessary dislocations is unrelated to theonset of twinning.