Laser-arc hybrid additive manufactured Al[sbnd]Cu alloy for T-shaped structure: Microstructure evaluation and molten pool behavior

Abstract

T-shaped structure is widely used in the aeronautic and aerospace industries for the development of lightweight applications. However, poor metallurgical bonding and thermal defects by remelting at the intersection is prone to occur in the additive manufacturing of the structure. In this study, T-shaped structure of AlCu alloy was fabricated by laser-arc hybrid additive manufacturing (LAHAM), and the molten pool behavior of the process was analyzed. According to the remelting of intersection, it was divided into the top layer and the remaining layers. The remelting zone of intersection (RZI) was obvious in the top layer. During the solidification of molten pool from the boundary to the center, the ratio of temperature gradient G to solidification rate R (G/R) at the S/L interface decreased from 2.57 × 108 (K·s)/m2 to 9.27 × 107 (K·s)/m2, and promoted the transformation of equiaxed dendrites. In the remaining layers, the recoil pressure, much smaller G/R and larger G∙R made the grains as fine equiaxed along the z direction in the laser zone (LZ), while coarse columnar were observed in the arc zone (AZ). Due to the microstructure changes, the deposited T-shaped structure exhibited a yield strength of 146.5 ± 2.2 MPa and an ultimate tensile strength of 290.3 ± 5.9 MPa.