| The addition of rare earth?RE?elements can improve the combination mechanical property of Mg alloys,which can enhance the ductility,corrosion resistance,heat resistance with no reduce of high specific strength and stiffiness of Mg alloys.Among various RE elements,yttrium?Y?shows an excellent effect on improving the ductility of Mg alloys.However,the mechanism of this improvement does not reach an agreement,which shows plenty of room for research.In this paper,Mg-5wt%Y extruded alloy showed excellent tensile ductility along the extrusion direction.An in situ tensile test with three-dimensional X-ray diffraction?3DXRD?identified prismatic,basal,and pyramidal<a>slip in different grains during deformation based on the analysis of grain rotation.Ex situ slip trace analysis using electron backscatter diffraction confirms the extensive activation of non-basal slip systems,which can explain the high ductility of this material.Critical resolved shear stress?CRSS?ratios between non-basal slip and basal slip are estimated from Schmid factor analysis.Approximately 180 grains were indexed among the two layers?90grains in each layer?.The specimen shows a typical extrusion texture,where the<0001>axis of most grains are perpendicular to the extrusion direction?Z?.The COMs of all indexed grains are within a 1200?m×1200?m square area,which is consistent with the 1mm×1mm cross-section area of the specimen.Nine grains that were tracked in most subsequent load steps were analyzed in detail for the slip activity in each of them.The result shows that the grains activitied by basal slip have a higher Schmid factor than the grains activitied by non-basal slip,which means the slip modes relate seriously to the ratio between non-basal slip and basal slip.The estimated ratio of CRSSprism/CRSSbasal is 1.8-2.7;the estimated ratio of CRSSpyramidal<a>/CRSSbasal is 1.6-1.8.Enhanced non-basal<a>slip can account for the high tensile ductility of the Mg-Y alloy. |
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