MICROSTRUCTURAL DEVELOPMENT DURING COLD DEFORMATION AND RECRYSTALLIZATION OF 2014 AL-AL2O3 PARTICULATE COMPOSITE

The recrystallisation behaviour has been studied in a cold worked 2014 Al-Al2O3 particulate reinforced composite which was heat treated to produce two markedly different initial matrix microstructures. The composite was cold deformed to a reduction of either 30 or 50% and then annealed for various times at temperatures in the range 100-500-degrees-C. The microstructural development during recrystallisation was studied using optical and transmission electron microscopy (TEM). The recrystallisation kinetics were monitored via hardness measurements and the results correlated with the microstructural analysis. It was observed that the kinetics and temperature of recrystallisation were dependent on the original heat treatment. A detailed TEM investigation indicated that nucleation occurs preferentially at individual and clustered Al2O3 particles, but the progress of recrystallisation was controlled by the distribution of dispersoid particles in the matrix. Recrystallisation proceeded rapidly in the composite containing large stable dispersoids. In contrast, when precipitation occurred during annealing, recrystallisation was severely retarded and was controlled by the fine precipitate dispersion.