SUPERPLASTIC BEHAVIOR OF A FINE-GRAINED 2-PHASE MG-9WT-PERCENT LI ALLOY

A two-phase Mg-9Li alloy (where the composition is in weight per cent) was made fine grained (d≈6-35 μm) by extensive cold rolling into foils and press bonding the foils at low homologous temperatures. The material exhibited superplastic properties in the temperature range 423-523 K ((0.49-0.61)T/Tm) with elongations to failure as high as 460%. The creep rate was determined to be inversely proportional to approximately the square of grain size and to the second power of stress. The activation energy for superplastic flow was equal to that for lattice diffusion in the major b.c.c. β phase. The Mg-9Li laminate alloy was found to be similar in its flow characteristics to MA-21, a multicomponent Mg-8.1Li fine-grained commercial Soviet alloy. © 1990.