Characteristics of superplasticity domain in the processing map for hot working of as-cast Mg-11.5Li-1.5Al alloy

Abstract

Processing map for hot working of as-cast Mg-11.5Li-1.5Al alloy has been developed in the temperature range 200 450degreesC and strain rate range 0.001-100 s(-1). The map exhibited a single domain with a peak efficiency of 65% occurring at 400degreesC and 0.001 s(-1). Under these conditions, the material exhibited abnormal elongation. On the basis of the elongation, the grain structure, the apparent activation energy for hot deformation (95 kJ mole (1)) and the peak efficiency of power dissipation (65% corresponding to a strain rate sensitivity of about 0.5), the domain is interpreted to represent superplasticity, At strain rates higher than about 10 s(-1), the material exhibits microstructural instability, while at temperatures of 450degreesC and it strain rate of 0.001 s (1), grain boundary cracking is observed