Origins of the mechanical property heterogeneity in a hybrid additive manufactured Hastelloy X

Hybrid additive manufacturing (hybrid-AM) technique is a new processing technique in which the large part of a component is fabricated by conventional manufacturing techniques and the complex parts are added flexibly via AM. This technique provides an efficient and economical method for manufacturing metallic components with different degrees of complexity. However, the mechanical properties of the substrate and the additive manufactured zone usually failed to match well while the underlying mechanism is still not fully understood. To address this problem, here we revealed the mechanisms of mechanical property heterogeneity in a hybrid-AMed Hastelloy X by microstructural characterization, thermo-mechanical simulations, and strengthening mechanism analyzing. The results demonstrate that the tensile properties and micro-hardness along the building direction show distinctive heterogeneity in the hybrid-AMed Hastelloy X, which is directly related to the evident microstructure changes. We attributed the microstructural variation to the different thermal histories of different regions during AM. Strengthening mechanism analysis indicated that the inhomogeneity of mechanical properties in the hybrid-AM Hastelloy X was mainly determined by the heterogeneous distribution of grain size, dislocation density, and crystallographic texture. EBSD, ECCI, and residual stress simulation all provided strong evidence for this conclusion. These findings shed new insights not only for achieving more homogeneous mechanical properties during the hybrid-AM process but also for laser additive repair and other fields.