In-situ TiC particles reinforced AA2219 Al-6.3Cu alloy joint via ultrasonic frequency double-pulsed arc

Enhancement in the mechanical properties of AA2219 Al-6.3Cu(wt.%) alloy arc-welded joints is a guarantee for an excellent service reliability of large aerospace components. This work demonstrates a novel strategy for reinforcing simultaneously in strength and ductility of Al-6.3Cu alloy arc-welded joint enabled by introducing TiC particles (TiC_p) embedding into filler wire assisted with a distinctive ultrasonic frequency double-pulsed (UFDP) arc. A fine-formation TiC_p/Al-6.3Cu joint characterized by refined α-Al equiaxed-grains in welded metal (WM) was successfully fabricated. Undergoing solution and aging treatments, the joint microstructure evolved into a hierarchical α-Al grain structure embedded with dense coherent θ''-Al₃Cu nano-precipitation (length ∼22.3 nm), which consists of refined, mediate-size and coarsen α-Al grains in WM, heat-affected zone (HAZ) and base metal (BM), respectively. Relying on a slight grain refinement strengthening and Orowan strengthening in WM, the yield and majority of plastic strain were confined into BM. The as-fabricated TiC_p/Al-6.3Cu joint exhibited an unprecedented joint coefficient of 93% (UTS 407 MPa) meanwhile an elongation of 16.4%. This work shares an inspiring view on the microstructural design of lightweight alloys arc-welded joint for an outstanding mechanical performance.