Controllable preparation of ultrafine bulk ODS W alloy with ultrahigh strength and improved ductility

Abstract

In order to alleviate the difficulties of coarse grains and poor mechanical properties in traditional hot worked bulk W alloys, we designed the entire chain preparation process including two-step freeze-drying, multi-step low temperature sintering and multi-step hot pressing. As a result, the hot worked bulk W-Y₂O₃ alloy in this work features finest grain size (650 nm) and finer subgrains, ultrafine intergranular and intragranular oxide nanoparticles (<50 nm), novel oxide compositions (Y₂WO₆ or Y₂O₃@Y₂WO₆ core-shell phase), and specific W(110)/Y₂WO₆ (232) (400), (432) or ($\overline{2}\overline{2}$2) coherent phase interfaces. Furthermore, the above microstructure characteristics endow W-Y₂O₃ alloy with highest strength (1401.0 MPa, 1284.4 MPa and 1039.1 MPa at 100 °C, 200 °C and 600 °C repectively), excellent ductility and outstanding structure thermal stability compare to traditional bulk ODS W alloy, which points out a new direction for the development of ex-situ precipitated second phase dispersion strengthened refractory metals.