A much higher elongation of a warm rolled superplastic Al-Li-Cu-Mg-Zr alloy was madeunder two-stage strain rate tests comparing with the single ones.During initial stage ofdeformation a deformation-induced continuous recrystallization which converted a subgrainstructure into a recrystallized grain structure by a continuous increase in boundarymisorientations had occurred.The higher the strain rate,the faster the continuousrecrystallization and the finer the recrystallized grains.The fine recrystallized grain structureformed during the first stage deformation is the essential condition for the material to havehigh strain rate hardening and strain hardening during the low second stage superplasticdeformation.The combination of strain rate hardening and strain hardening is the reason whythe higher elongation may be obtained during two-stage superplastic deformation of the alloy.
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