Improving the laser powder bed fusion processability of A2618 alloy: Investigation on TiB2 addition strategies via single scan track approach

Processing aluminum alloys by Laser Powder Bed Fusion (L-PBF) is of great interest for components production in various industries; however, their processability is quite challenging due to their susceptibility to solidification cracking. One effective strategy to overcome this problem is the addition of inoculants to modify their solidification mechanism and to prevent crack initiation. In this context, this study focuses on the processability of the A2618 alloy with the addition of TiB2 as an inoculant using different ex situ strategies: low- and high-energy mechanical mixing and plasma coating respectively. The Single Scan Tracks (SSTs) approach was used to investigate the quality and stability of tracks that greatly influence the quality of printed parts and optimize the process parameters for the three feedstocks. The comparison between the systems enabled the identification of slight differences between powders in terms of the processability window, revealing the influence of the inoculant dispersion method on the processability of the A2618 alloy. Electron Backscatter Diffraction (EBSD) analysis carried out on the SST cross-sections confirmed significant differences between the three powders in terms of grain refinement. In addition to the microstructure refinement and the absence of solidification cracks, the analysis revealed the effectiveness of the plasma coating method which allows for obtaining a uniform and homogeneous distribution of the reinforcement on the aluminum particles' surface. Bulk samples were then produced to validate the optimization study results: the characterization of the cubic samples revealed a dense (99.9%) and crack-free microstructure, with a homogeneous distribution of the reinforcement phase.