Refinement of A356 alloy using continuous rheological extrusion Al-Ti-V-B master alloy

Abstract

Based on thermodynamic calculations and continuous rheological extrusion (CRE) technology, Al-Ti-V-B master alloys were designed and prepared. The morphology and the distribution of the refined phases in the master alloys were analyzed by XRD, SEM, and TEM. The effects of master alloy addition and holding time on the microstructure and mechanical properties of A356 alloy were investigated. Under the optimum refiner addition of 0.3wt.% and the holding time of 20 min, the average grain size of the refined A356 alloy is 151.8±9.11 µm, 89.62% lower than that of original A356 alloy. The tensile strength and elongation of as-cast A356 refined alloy are 196.11 MPa and 5.75%, respectively. After T6 treatment, the tensile strength and elongation of A356 refined alloy are 290.1 MPa and 3.09%, respectively. The fracture morphology is characterized by a predominance of along-crystal fracture with a small amount of through-crystal fracture, attributed to the refined grains. Finer grains promote crack path deflection and localized plastic deformation, enhancing energy dissipation and reducing the tendency for brittle fracture. This study provides a novel approach to improving the mechanical properties of A356 alloy through grain refinement using CRE Al-Ti-V-B master alloy.