Strong yet ductile self-passivating W-10Cr alloy by laser powder bed fusion

Compared to pure tungsten, self-passivating tungsten alloys (SPTAs) for the future nuclear fusion armour are expected to offer a major safety guarantee in a loss-of-coolant accident (LOCA) event. Here we used laser powder bed fusion (LPBF) to print a self-passivating W-10Cr system. The main challenges for processing W-10Cr alloys are balling phenomena and chromium loss due to their melting point differences. After laser parameters optimizations, W-10Cr blocks with relatively dense and smooth surface were fabricated. As-built specimens exhibited an inhomogeneous microstructure with W-rich regions and Cr-rich ones. In the Cr-rich region, ultrafine equiaxed grains were obtained in view of Spinodal decomposition. Owing to the co-contribution of Spinodal decomposition and fine-grain structure, the compressive strength, fracture strain and Vickers hardness (HV0.005) of W-10Cr alloy reach 1451 MPa, 21.5% and 9.4 GPa, which are obviously superior to pure tungsten counterparts, with the improvement of 41%, 115% and 43%, respectively. Based on the indentation responses, as-measured indentation hardness followed typical indentation size effect (ISE). A higher contribution from elastically surface work in the early part of indentation is responsible for the hardening mechanism of W-10Cr alloy. Additionally, the strengthening and toughening mechanisms associated with improved properties are also discussed. The mechanistic insights into the deformation behavior have extensive implications for the development of additively manufactured SPTAs with exceptional mechanical properties. •A W-10Cr self-passivating alloy was first printed in situ via LPBF.•The laser energy density of ∼313 J/mm3 led to highest properties.•Fine-grain structures were obtained due to Spinodal decomposition.•As-measured indentation hardness followed typical indentation size effect.•Improved properties were attributed to the fine-grain strengthening, etc.