Study on thermal deformation behavior and microstructural evolution of 2 wt. % Al–Ti–C/7075Al composite materials

Abstract

Al–Ti–C/7075 aluminum matrix composites (referred to as 7075-ATC) containing uniformly distributed TiC particles and traces of TiAl₃ particles were produced by introducing 2 wt. % Al–Ti–C master alloy through stir casting. Isothermal thermal compression behavior at 300 °C–450 °C and 0.001 s⁻¹ to 1 s⁻¹ strain rates was studied in a Gleeble-3800 thermal simulation tester. Peak stress is influenced by deformation temperature and strain rate, reaching its maximum at low temperatures and high strain rates. The activation energy of the final thermal deformation is 150.11 kJ/mol, attributed to particle reinforcement. A sinusoidal hyperbolic Eigen structure equation for composites considering strain compensation is developed to describe the rheological stresses in composites. Dynamic recrystallization at 450 °C and a strain rate of 0.001 s⁻¹ enhances composite molding properties. After hot compression, composites exhibit higher activation energy (Q) than cast 7075 and in situ particle-reinforced 7075 due to the obstruction of dislocations by the particles, grain refinement, and pinning effect on the grains. Based on the experimental results, an intrinsic model considering strain compensation was developed to accurately predict the thermal deformation behavior. EBSD results indicated that dynamic softening primarily occurred through dynamic restitution and partial recrystallization. The efficiency of softening peaked at 39% under a strain of 0.6, deformation temperatures between 350 °C and 450 °C, and strain rates ranging from 0.0009 s⁻¹ to 0.0111 s⁻¹.