Microstructure and strain rate sensitivity of Mg-11Li-3Al-1Ca alloy

Abstract

As-cast and extruded Mg-11Li-3Al-1Ca alloys were successfully prepared. The microstructure of specimens was analyzed with OM, SEM, EDS and XRD. It was found that as-cast specimens were composed of β phase (Lithium), small pieces of divorced eutectic α phase (Magnesium), MgLi2Al and Al2Ca compounds. During the extrusion process, the microstructure was refined and partial recrystallization was observed. Uniaxial tension tests were carried out under different strain rate. The ultimate intensities were obviously higher than common β phase Mg-Li alloys to compare with past studies. Deformation capacity of the extruded specimen at room temperature was estimated by strain-rate sensitivity exponent (m value), which was 0.071. Serrated flows were apparent through out the deformation history and the phenomenon was interpreted through the competition between dynamic strain aging (DSA) of solute atoms and shearing of precipitates by dislocations. © 2010 The Japan Institute of Metal.