Porosity in cored-wire-arc directed energy deposition of TiC/Al composite: formation mechanism and inhibition strategy

Porosity is an unavoidable problem in aluminium alloy wire-arc directed energy deposition (DED), becoming even more prominent in aluminium-matrix powder core wires, which significantly limits their performance and application potential. This study combines wire-arc DED technology with Al-matrix powder cored wire for the first time, successfully fabricating monolayer and multilayer composite components using a custom-designed TiC/Al-matrix powder core wire. The pore types and formation mechanisms in cored-wire-arc DED TiC/Al composites were systematically investigated. The findings indicate that: (1) Compared to conventional aluminium alloys, the Al-matrix powder core wire exhibited larger pores and higher porosity. Additionally, a novel pore type, enclosed by Ti and Si elements, was identified. (2) Pores concentrate near specimen edges due to the migration, aggregation, and prolonged stabilisation of large bubbles in the melt pool. (3) To mitigate porosity, strategies of spiral arc oscillation (SO) and ultrasonic vibration assisted (UA) was innovatively introduced, which effectively reducing porosity levels. SO enhances melt pool flow, reducing porosity by 47% relative to as-deposited (AD) specimens. UA induces cavitation effects and acoustic flow, enhancing Marangoni flow and reducing porosity by 63% in SO + UA specimens. This study presents a novel approach for high-performance aluminium-matrix composite fabrication.