Recent advances in inoculation treatment for powder-based additive manufacturing of aluminium alloys

Powder-based additive manufacturing (AM) is revolutionizing the fabrication of advanced engineering metallic materials, including aluminium (Al) alloys, which are the workhorse materials in automobile and aerospace industries. However, challenges remain in the wider applications of AM to produce Al components due to the high tendency to form coarse, textured columnar grains, which causes hot-cracking and severe property anisotropy. The recent adoption of inoculation treatment in AM of Al alloys has been successful in achieving grain refinement, cracking elimination and property improvement, which is a step forward in this field. This paper surveys the emerging researches on inoculation treatment of AM-fabricated Al alloys and provides a comprehensive overview of different inoculation techniques for AM, the refining efficiencies of various inoculants and their underlying mechanisms. The uniqueness of this review includes substantive discussions on the mechanism of epitaxial grain growth during AM and a succinct comparison of the refining efficiency based on both experiment and crystallographic modelling. Critical challenges in the most recent alloy design strategy embedded with inoculation treatment are also discussed. Accordingly, outlooks for the immediate future in this area, gaps in the scientific understanding, and research needs for the expansion of AM in fabrication high-performance Al alloys are provided.