Superplastic behavior of reciprocating extruded Mg-6Zn-1Y-0.6Ce-0.6Zr from rapidly solidified ribbons

Abstract

RRE-Mg66 alloy with a composition of Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6Zr was prepared by combinatorial processes of rapid solidification, reciprocating extrusion and extrusion. Microstructure was evaluated on SEM and TEM. The average grain size of the alloy is 0.7 μm, the size of the second phase at grain boundary is 0.15 μm, and the size of the intragranular precipitates in round shape is less than 20 nm. Superplastic behavior of the material was investigated in a temperature range of 150 to 250 °C and initial strain rate range of 3.3×10⁻⁴ to 3.3×10⁻² s⁻¹ in air. The highest elongation of 270% was obtained at 250 °C and 3.3× 10⁻³ s⁻¹. High-strain-rate superplasticity and low-temperature superplasticity were achieved. The superplasticity results from intragranular sliding (IGS) at temperatures from 170 to < 200 °C and grain boundaries sliding (GBS) at 250 °C. At 200 °C a combination of IGS and GBS contributes to the superplastic flow.

Keywords

rapid solidification / reciprocating extrusion / extrusion / superplasticity

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