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 Y 2 O 3 and TiC particles were simultaneously doped into Mo alloys using ball-milling and subsequent low temperature sintering. Accompanied by TiC addition, the Mo−Y 2 O 3 grains are sharply refined from 3.12 to 1.36 µm. In particular, Y 2 O 3 and TiC can form smaller Y−Ti−O−C quaternary phase particles (∼230 nm) at Mo GBs compared to single Y 2 O 3 particles (∼120 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, Y 2 O 3 , 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−Y 2 O 3 , and Mo−Y 2 O 3 −TiC alloys have similar relative densities (97.4%–98.0%). More importantly, the Mo−Y 2 O 3 −TiC alloys exhibit higher hardness (HV 0.2 (425 ± 25)) compared to Mo−Y 2 O 3 alloys (HV 0.2 (370 ± 25)). This work could provide a relevant strategy for the preparation of ultrafine Mo alloys by facile ball-milling.
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