Rolling-assisted laser directed energy deposition of Hastelloy X: experimental and numerical studies

Additively manufactured Hastelloy X (AM HX) typically features porosity and columnar grains due to directional heat flux, which causes anisotropy in mechanical properties. In this study, an in-situ rolling process was applied into laser directed energy deposition (L-DED) to fabricate this alloy. It was found that the rolling applied to every deposition layer can effectively squeeze the pores, refine the elongated grains, leading to an equiaxed grain structure with an average size of ∼24 μm and weakened texture. This leads to an apparent improvement in the tensile yield stress at room temperature compared to the unrolled condition (from 341 MPa to 651 MPa) while maintaining good ductility, as evidenced by a uniform elongation of around 10 %. Finite element analysis (FEA) confirms that rolling-assisted L-DED induces normal and shear stresses, resulting in dendrite fragments and stored strain. This stored strain serves as the site for metadynamic recrystallization during subsequent thermomechanical processes.