Hot Deformation and Processing Maps of B4C/6061Al Nanocomposites Fabricated by Spark Plasma Sintering

We developed 3 vol.% B4C/6061Al nanocomposites by spark plasma sintering. We then characterized their flow and hot deformation behaviors using isothermal compression tests at deformation temperatures of 673-823 K and strain rates of 0.001-1 s(-1). Results indicated that their steady flow characteristic can be described by the Zener-Hollomon parameter (Z) as a hyperbolic-sine function of flow stress. Based on pinning effect from B4C nanoparticles, the estimated activation energy was calculated to be 274.80 kJ/mol. At the unstable deformation condition (723 K/1 s(-1)) with high Z, flow localization appeared; the main softening mechanisms involved are dynamic recovery and dynamic recrystallization (DRX). At the stable deformation condition (823 K/0.001 s(-1)) with low Z, adequate DRX occurred. Based on the processing map and microstructure evolution, the optimum hot working conditions for B4C/6061Al nanocomposites were determined to be a deformation temperature of 773-823 K and a strain rate of 0.001-0.003 s(-1). These working conditions were verified by a hot extrusion test.