Abstract:In situ TiB₂ reinforced 6351 Al alloy composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 10 s⁻¹ and from 300 to 550 ℃, respectively, using Gleeble−1500D system. And the associated microstructural transformations and instability phenomena were studied by observations of the optical and transmission electron microscope. The power dissipation efficiency and instability parameter were calculated following the dynamic material model and plotted with the temperature and logarithm of strain rate to obtain processing maps for strains of 0.2, 0.4, and 0.6. The processing maps present the instability zones at higher strain rates. The result shows that with increasing strain, the instability zones enlarge. The microstructural examination shows that the interface separates even the particle cracks or aligns along the shear direction of the adiabatic shear band in the instability zones. Two domains of higher efficiencies correspond to dynamic recovery and dynamic recrystallization during the hot deformation. Using the processing maps, the optimum processing parameters of stain rates and temperatures can be chosen for effective hot deformation of TiB₂/6351 composites.

Key words: TiB₂/6351 composites; processing maps; dynamic recrystallization; flow instability