Journal
SCRIPTA MATERIALIA
Volume 221, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.scriptamat.2022.114966
Keywords
High-entropy alloys; Wear resistance; bcc to hcp transition; High-resolution transmission electron microscopy; Partial dislocation dipole; Atom shuffling
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Funding
- Fundamental Research Program of Shenzhen Science and Technology Innovation Commossion [JCYJ20210324131405015]
- Innovation and Technology Commission (ITC) of the Government of the HKASR, China
- PolyU Research Office [BBR1, BBX2]
- Research Committee of PolyU [RK3J, RK2N]
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In this paper, cold rolling and different annealing temperatures were applied to the as-cast TiZrHfTa0.5 alloy. The study found that the most bcc -> hcp phase transition occurred in the cold-rolled plus 870 degrees C-annealed specimens. Atomic-scale observations revealed that this phase transition was further activated in the self-organized gradient worn subsurface, where a dual-phase structure with increased hcp phase fraction accommodated the sliding-caused plasticity.
In this paper, cold rolling (55% reduction in thickness) plus different annealing temperatures were performed on the as-cast TiZrHfTa0.5 metastable refractory high-entropy alloy. The most bcc -> hcp phase transition was found in the cold-rolled plus 870 degrees C-annealed specimens (average grain size of similar to 30 mu m), which exhibit the lowest coefficient of frictions (0.12-0.15) and wear rates ((4.08-9.68) x 10(-5) mm(3)/N m) under the dry-sliding loads of 16 N to 64 N at room temperature, relative to the as-cast and cold-rolled specimens with lower annealing temperatures. Atomic-scale observations revealed that composition-segregated bcc -> hcp phase transition is further activated in the self-organized gradient worn subsurface, where the dual-phase structure with increased hcp phase fraction continues accommodating the repeated sliding-caused plasticity. Accordingly, two kinds of atomic movement mechanisms of bcc -> hcp phase transition were dissected to be mainly executed by the cooperation of atom shuffling or/and partial dislocation dipoles gliding.
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