Role of Inoculant Particles in Microstructure and Microhardness of Additively Manufactured Aluminum Alloys

Additive manufacturing (AM) of high strength aluminum alloys has traditionally been difficult due to solidification cracking; however, inoculants and weld pool agitation have been shown to mitigate these issues through grain refinement. While inoculation is increasingly applied in wire arc additive manufacturing (WAAM), the distribution and effect of inoculant particles within WAAM builds remains poorly characterized. Wire feedstocks of AA6061 and AA7075 inoculated with titanium and B₄C particles were deposited using WAAM and subsequently heat treated to the T6 and T73 conditions. Automated imaging combined with artificial intelligence (AI) assisted image analysis was then used to quantify inoculant particle characteristics over large cross-sectional areas, enabling higher throughput measurements than manual annotation. Because the inoculant particles are significantly harder than the α-Al matrix, preparation and etch development studies were performed to allow proper characterization of the material. Microhardness was measured for all conditions to assess localized mechanical response, and hardness trends were examined in relation to the quantified inoculant particle populations and other microstructural attributes. This work provides key insights into inoculant particle distributions in WAAM AA6061 and AA7075 and their relationship to microhardness and microstructure, supporting improved process–structure–property understanding for these aluminum alloys.