Content effects of in-situ synthesis TiC for grain refinement, porosity suppression and performance enhancement in wire arc additive manufactured Al-Cu alloy

Abstract

In wire arc additive manufactured (WAAM) Al-Cu alloys, coarse microstructure and porosity defects have long been critical factors limiting their performance. Fortunately, recent studies have shown that incorporating ceramic particles into additively manufactured components can effectively mitigate these issues. However, developing composite materials in WAAM remains a challenge. Hence, this study successfully fabricated Al-Cu alloy wire with varying TiC content (0.6, 1.2, 2.0 wt%) using an in-situ molten salt reaction method and systematically investigated its enhancement mechanisms on WAAM Al-Cu alloy. The results reveal that TiC addition significantly refines the grain structure, reduces porosity, and enhances mechanical properties. Notably, the alloy containing 1.2 wt% TiC exhibited the best overall properties, achieving a yield strength of 127.5 MPa, an ultimate tensile strength of 311.1 MPa, and an elongation of 12.4 %. Mechanistic analysis reveals that the grain refinement was primarily attributed to enhanced heterogeneous nucleation and the effective inhibition of grain boundary migration. The strengthening mechanisms were dominated by three dominant mechanisms: (i) grain refinement strengthening via the Hall-Petch effect induced by TiC particles, (ii) Orowan strengthening resulting from the dispersion of rigid TiC particles within the matrix, and (iii) Load-bearing strengthening enabled by robust interfacial bonding between TiC particles and the matrix. Furthermore, the improvement in ductility was mainly attributed to porosity reduction, a full columnar-to-equiaxed transition (CET), refined grain structures, and the formation of uniformly distributed fine precipitates. This study highlights the critical role of ceramic particle (TiC) content in optimizing WAAM Al-Cu alloy, offering valuable insights for designing and manufacturing of high-performance large-scale aluminum alloy components.