Wire arc additive manufacturing of components using TiC/Ti reinforced Al-Zn-Mg-Cu alloy wire: Microstructure evolution, strengthening mechanism, and fracture behavior

This study addresses the challenges of uneven microstructure and hot cracking in wire arc additive manufacturing (WAAM) Al-Zn-Mg-Cu alloy, and the crack-free high-performance components were successfully prepared using cold metal transfer-based WAAM with TiC/Ti reinforced Al-Zn-Mg-Cu alloy wire. The results indicate that the microstructure of the as-deposited and T6 heat-treated samples comprises fine equiaxial grains, with an average size of approximately 8–9 μm. The grain refinement is mainly dependent on the heterogeneous nucleation of L12-Al3Ti phase, the constitutional supercooling zone formed by the Ti element, and the physical blocking growth layer of TiC particles. Compared to the as-deposited sample, the ultimate tensile strength of the T6 heat-treated sample in the horizontal direction reached 578.5 ± 5.6 MPa (an increase of 49.3 %), and the elongation was 6.4 ± 0.3 % (a decrease of 13.5 %). It is found that the high mechanical properties of the T6 heat-treated samples are mainly attributed to the combined effects of fine grain strengthening (67.1 MPa), solid solution strengthening (60.6 MPa) and precipitation strengthening (339.1 MPa). Additionally, both the as-deposited and T6 heat-treated samples presented a mixed fracture model, with cracks initiating at the brittle hard phase(L12-Al3Ti and Al18Mg3Ti2) and grain boundary, and then primarily propagating along the grain boundary. © 2024 Elsevier Inc.