Hot Deformation Behavior and Workability of (SiCp + Mg2B2O5w)/6061 Al Hybrid and SiCp/6061 Al Composites

The hot deformation behavior of (3 vol% SiCp + 3 vol% Mg2B2O5w)/6061 Al (W3P3) hybrid composite and 6 vol% SiCp/6061 Al (P-6) composite have been characterized in the temperature range of 300-450 degrees C and strain rate range of 0.0001-0.1 s(-1) using isothermal constant true strain rate tests. The flow behavior and processing maps have been investigated using the corrected data to eliminate the effect of friction. Under the same deformation conditions, the compressive resistance of the singular composite remains superior to that of the hybrid composites. The processing map of W3P3 hybrid composite exhibits a single hot working domain at the temperature between 350 and 450 degrees C with strain rate between 0.0001 and 0.003 s(-1) (domain A). Two hot working domains exist for P6 composite: (i) 300-400 degrees C/0.0001-0.003 s(-1) (domain B1); (ii) 380-450 degrees C/0.01-0.1 s(-1) (domain B2). The processing maps also reveal the flow instability of the two composites, which is associated with whiskers breakage, whisker/matrix interfacial debonding, SiCp/matrix interfacial decohesion, adiabatic shear bands or flow localization, and wedge cracking in the corresponding regions. The estimated apparent activation energies are about 224 kJ mol(-1) in domain A for W3P3 hybrid composite, 177 kJ mol(-1) in domain B1 and 263 kJ mol(-1) in domain B2 for P-6 composite, respectively. These values are higher than that for self-diffusion in Al (142 kJ mol(-1)), suggesting that there is a significant contribution from the back stress caused by the presence of particles and/or whiskers in the matrix. The deformation mechanisms corresponding to domain B1 and domain B2 are dislocation climb controlled creep and cross-slip for P-6 composite, respectively. For W3P3 hybrid composite, the deformation mechanisms contain dislocation climb controlled creep and grain boundary sliding caused by DRX in domain A.