Manifestations of dynamic strain ageing in 2090 Al-Li alloy

The manifestations of dynamic strain ageing in a commercial 2090 Al - Li alloy were investigated in a wide range of temperatures (-40 to 100 degrees C) and strain rates (4.16x10(-5) to 4.16x10(-3) s(-1)). Serrated yielding, as a macroscopic manifestation of dynamic strain ageing, occurs under all testing conditions. Negative strain-rate sensitivity of the flow stress is also observed. Temperature rise and strain rate reduction cause the increase of the yield strength and the work-hardening rate, as well as the decrease of elongation - the behavior being typical for the range in which C-type serrations appear. These phenomena are related to the dislocation substructure, in which features characteristic for solute atoms blocking of dislocations and Orowan bypassing are observed