Dissolving and Stabilizing Soft WB2 and MoB2 Phases into High-Entropy Borides via Boron-Metals Reactive Sintering to Attain Higher Hardness

• DOI: 10.48550/arxiv.1912.11743
• Publication Date: 2019-01-01
• Authors: Mingde Qin; Joshua Gild; Haoren Wang; Tyler Harrington; Kenneth S. Vecchio; Jian Luo
• Keywords: Spark Plasma Sintering; Chemical Mechanical Planarization; High-Entropy Alloys

Five single-phase WB2- and MoB2-containing high-entropy borides (HEBs) have been made via reactive spark plasma sintering of elemental boron metals. A large driving force enables the full dissolution 10-20 mol. % WB2 to form dense, HEBs, including (Ti0.2Zr0.2Hf0.2Mo0.2W0.2)B2, (Ti0.2Ta0.2Cr0.2Mo0.2W0.2)B2, (Zr0.2Hf0.2Nb0.2Ta0.2W0.2)B2, (Zr0.225Hf0.225Ta0.225Mo0.225W0.1)B2; successful fabrication such WB2-containing HEBs has not reported before. In processing science, this result serves perhaps best example demonstrating that phase formation in ceramics can strongly depend on kinetic route. scientifically interesting finding is containing softer and/or MoB2 components are significantly harder than (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 (with binary boride components). This exemplifies achieve unexpected properties.