Laser additive repairing of high-strength 6061 aluminum alloy components

The high replacement cost of damaged high-strength aluminum (Al) alloy components in rail transit systems necessitates the development of reliable repair technologies. However, laser additive repair (LAR) of such alloys is often hindered by hot cracking, limiting their restorative potential. Here, we introduce tantalum (Ta) as an innovative grain refiner, which operates through the in-situ formation of Al 3 Ta intermetallic compounds that act as heterogeneous nucleation sites and inhibit grain boundary migration during solidification. This mechanism effectively mitigates hot cracking and enables robust LAR of high-strength 6061 Al alloy camshaft housing covers used in HXN3 diesel locomotives. Our results demonstrate that the addition of 2 wt% Ta effectively suppresses hot-tearing, suppresses columnar grain structures, and promotes significant grain refinement. Following the aging treatment, the 6061-Ta alloy achieves an optimal strength-ductility balance, with a tensile strength of ∼312 MPa and elongation of ∼8%, meeting the stringent specifications of GB/T 32182-2023 standard for railway application. Crucially, when applied to pre-experimental repairs of 6061 substrates, the 6061-Ta powder exhibits superior interfacial bonding strength, satisfying the requirements for LAR camshaft housing cover. The successful implementation of this protocol on actual components confirms its industrial viability. These findings establish Ta-modified 6061 alloy as a transformative material system for high-integrity LAR applications in railway maintenance, offering both technical and economic benefits for sustainable component lifecycle management.