Microstructure refinement and second phase particle regulation of Mo–Y₂O₃ alloys by minor TiC additive

The oxide dispersion strengthened Mo alloys (ODS-Mo) prepared by traditional ball milling and subsequent sintering technique generally possess comparatively coarse Mo grains and large oxide particles at Mo grain boundaries (GBs), which obviously suppress the corresponding strengthening effect of oxide addition. In this work, the Y₂O₃ and TiC particles were simultaneously doped into Mo alloys using ball-milling and subsequent low temperature sintering. Accompanied by TiC addition, the Mo–Y₂O₃ grains are sharply refined from 3.12 to 1.36 μm. In particular, Y₂O₃ and TiC can form smaller Y–Ti–O–C quaternary phase particles (~230 nm) at Mo GBs compared to single Y₂O₃ particles (~420 nm), so as to these new formed Y–Ti–O–C particles can more effectively pin and hinder GBs movement. In addition to Y–Ti–O–C particles at GBs, Y₂O₃, TiO_x, and TiC_x nanoparticles (<100 nm) also exist within Mo grains, which is significantly different from traditional ODS-Mo. The appearance of TiO_x phase indicates that some active Ti within TiC can adsorb oxygen impurities of Mo matrix to form a new strengthening phase, thus strengthening and purifying Mo matrix. Furthermore, the pure Mo, Mo–Y₂O₃, and Mo–Y₂O₃–TiC alloys have similar relative densities (97.4%–98.0%). More importantly, the Mo–Y₂O₃–TiC alloys exhibit higher hardness (HV_0.2 (425 ± 25)) compared to Mo–Y₂O₃ alloys (HV_0.2 (370 ± 25)). This work could provide a relevant strategy for the preparation of ultrafine Mo alloys by facile ball-milling.