Mechanical properties and Hall-Petch relationship of the extruded Mg-Zn-Y alloys with different volume fractions of icosahedral phase

초록

The effect of the volume fraction (0.6-8.4%) of the icosahedral phase (I-phase) on the microstructure, texture and mechanical properties of extruded Mg-Zn-Y alloys was examined. During extrusion, the eutectic and divorced eutectic I-phase in the cast microstructures was broken into small particles, and the particles were dispersed along the extrusion direction, forming parallel particle bands. The broken Iphase particles promoted grain refinement via a particle-stimulated nucleation mechanism and led to basal texture weakening through dynamic recrystallization. The work hardening rate increased with an increase in the volume fraction of I-phase. However, the strength decreased with an increase in the volume fraction of I-phase due to the texture softening effect. To incorporate the texture softening effect into the Hall-Petch relation, a modified Hall-Petch equation, which simultaneously considers the effects of grain size and texture on strength, was developed using the Schmid factors for basal slip. The proposed equation predicts smaller Hall-Petch slope, friction stress and yield strength with easier activation of basal slip, agreeing with the experimental observations. (C) 2018 Elsevier B.V. All rights reserved.

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