Influence of extrusion conditions on the superplastic properties of a Mg-8%Li alloy processed at room temperature by equal-channel angular pressing

Furui, M., Kitamura, H., Anada, H. and Langdon, T.G. (2006) Influence of extrusion conditions on the superplastic properties of a Mg-8%Li alloy processed at room temperature by equal-channel angular pressing. Kainer, K.U. (ed.) In Magnesium: Proceedings of the 7th International Conference on Magnesium Alloys and their Applications. Wiley-VCH Verlag. pp. 419-424 .

Abstract

It is well known that alpha+beta duplex structure Mg-Li alloys exhibit an excellent superplastic ductility at intermediate temperatures. Moreover, many researchers have demonstrated that the ductility enhancement in Mg alloys could be achieved by refining its grain structure using conventional thermo-mechanical treatments, powder metallurgy and severe plastic deformation. Among the severe plastic deformation methods, equal-channel angular pressing (ECAP) can produce uncontaminated, fully dense and large bulk materials with submicrometer or even nanometer grain structures effectively.
Processing by ECAP was successfully performed on a Mg-8mass%Li alloy at room temperature using a solid die having an internal channel angle of 135 degree. A refined and uniform dispersion of the alpha and beta phases was achieved by applying ECAP processing for four passes at room temperature by comparison with the alloy in the extruded condition. The elongations to failure in tensile testing increase with a decrease in the extrusion temperature but they are reasonably independent of the extrusion speed within the range from 1-10mm/s. The Mg-8%Li alloy exhibits excellent superplastic properties at 473K after extrusion and ECAP including a maximum elongation of 1780%. The strain rate sensitivity was measured as 0.4-0.6 under the optimum superplastic conditions.

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Contributors

Author: T.G. Langdon

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