Improving mechanical properties of wire + arc additively manufactured maraging steel through plastic deformation enhanced aging response

Maraging steel gains ultrahigh strength through aging; however, wire + arc additively manufactured maraging steel features a columnar-dendritic structure with associated segregation and shows a much less pronounced aging response. In this paper, plastic deformation was introduced through interpass cold rolling during the layer-by-layer deposition process. After aging, mechanical testing showed a substantial strength improvement from 1410MPa (unrolled) to 1750MPa (50kN rolled). Rolling induced partial recrystallisation to break the dendritic structure and form high-angle grain boundaries, which promoted the atoms diffusion to enable a more uniform solutionizing process and improved the subsequent aging response by 105-110%. The main contribution of overall strengthening of the rolled alloy was attributed to the effective aging process, accounting for more than 95% of the entire strength increase.