Ultrasonic assisted equal channel angular extrusion (UAE) as a novel hybrid method for continuous production of ultra-fine grained metals

The propagation of high-intensity ultrasonic vibration (UV) into metals can influence on mechanical and microstructure properties. The main objective of this research is to introduce a new hybrid method for improving limitations of the conventional equal channel angular extrusion (CECAE) process by using superimposed ultrasonic vibration on billet in the plastic deformation zone (PDZ) directly. The experimental set-up was designed and fabricated for the UAE process of commercially pure aluminum (99.5%) with two distinct wave propagation directions as laterally (L-UAE) or vertically (V-UAE). By combining of high-intensity UV with the ECAE process, ultra-fine grained (UFG) aluminum with grain size about ~2 µm was attained only with one pass, enabling even higher values of microhardness on processed samples. Moreover, the required load with UAE was about 30% lower than CECAE. Finite element simulations further confirmed the more plastic deformation during UAE than CECAE. The use of UV vertically against extrusion direction (V-UAE) showed better homogeneity in strain, grain size and hardness distributions.