Evolution of Y2O3 precipitates in ODS-316 L steel during reactive-inspired ball-milling and spark plasma sintering processes

Abstract

In this work, reactive-inspired ball-milling (RBM) and spark plasma sintering (SPS) were employed to produce an ODS-316 L steel. The evolution of Y2O3 particles during RBM and SPS processes was investigated, and the powder milled for different times was characterized for exploring the precipitation and coarsening behaviors of Y2O3 particles. It was found that Y2O3 particles with a metastable hexagonal structure precipitated in the early stage of ball-milling, and gradually transformed to a stable body centered cubic (BCC) structure during subsequent growth process. The size of Y2O3 particles maintained at about 3–4 nm and no longer increased significantly in the RBM stage, but their average size increased rapidly to about 12 nm after SPS. The HRTEM results of the alloy after SPS showed that Y2O3 particles inside the grains had a semi-coherent interface with the matrix. Compared with other methods, the united technology of RBM and SPS could significantly improve the tensile properties of the ODS-316 L steel. It was considered that the successful introduction of uniform and fine Y2O3 particles by RBM and the small size of austenite grains due to rapid sintering of SPS were responsible for the improved tensile properties.