Solidified structure and mechanical properties control of 2319 aluminum alloy for ultrasonic vibration-assisted arc-directed energy deposition with different amplitudes

Abstract

This study utilized ultrasonic vibration (UV) as an auxiliary method for 2319 Al-Cu alloy prepared by arc-directed energy deposition (arc-DED) to address the poor internal quality and mechanical properties of arc-DEDed components due to high heat input and thermal cycling effects. The effects of different ultrasonic amplitudes on the solidification structure and mechanical properties of Al-Cu alloys were investigated. Results indicated that applying UV with 10 μm amplitude effectively suppresses metallurgical defects in the microstructure of as-built 2319 aluminum alloy and cleanses their inter-layer interfaces. Compared with the non-UV sample, under the action of UV with the amplitude of 10 μm, the grain size refinement reaches a maximum of 25 %. UV improves molten pool fluidity and reduces temperature gradients. However, UV with large amplitude can trigger excessive ultrasound heat effects and intense cavitation behavior, which is not conducive to improving the uniformity and refinement of the solidified microstructure. After UV treatment, the elongation of arc-DEDed 2319 Al-Cu alloy significantly increases, with improvements of 111.9 % (amplitude of 10 μm), 88.1 % (amplitude of 20 μm), and 61.2 % (amplitude of 30 μm) under different amplitude conditions. The UV with 10 μm amplitude can transform the intergranular fracture induced by pores and brittle second phases in the non-vibrated specimens into transgranular fracture, significantly enhancing the plasticity and toughness of the material. Based on this, the UV with 10 μm amplitude plays a significant role in grain refinement, defect healing, and the improvement of mechanical properties.