Critical strain / Recrystallization of an aluminium alloy

The aluminium alloy-2618 is a precipitation hardening alloy, used for various aircrafts and other engineering applications. The Al-Cu- Mg alloy containing approx. 2.5% Cu, 1.5% Mg, and small amounts of Ni, Fe, and Si, remainder Al, was deformed by rolling and stretching uniaxially, with reduction upto 25%. The materials was annealed from 460 to 540 degree C for 1 hour and the resulting microstructures were analyzed Critical strains for recrystalization were identified. The effect of initial grain size on critical strain was also studied. Size and volume fraction of recrystallized grains were Measured with the help of image analyzer. Variations in the values of critical strains and the subsequent grain growth have been co-related with initial grain size and annealing temperature. The deformation mode, rolling or uniaxial stretching had an effect on the critical strain values for Al-alloy 2618. (author)