Abstract
Multi principal element alloys have attracted interests as a promising way to balance the bottleneck of the “inverse relationship” between high hardness and high fracture toughness. In the present study, the authors demonstrate the effects of Ti addition on the microstructures and mechanical properties of the CoCrFeNiTix alloys (x values in molar ratio, x = 0.7, 1.0, and 1.2), which exhibits a multi-phase structure containing face-centered cubic phase and various secondary phases, such as sigma, Laves, and (Cr,Fe)-rich phase. Throughout the combined experimental examination and modeling, we show that superb hardness (~9.3 GPa) and excellent compressive strength (~2.4 GPa) in our alloy system are attributed to solid-solution strengthening of the matrix and the formation of hard secondary phases. In addition, high indentation fracture toughness is also derived from the toughening mechanism interplay within the multiple-phase microstructure. At the fundamental level, the results suggest that multi-principal element alloys containing dual or multi-phase structures may provide a solution for developing structural alloys with enhanced strength-toughness synergy.
Highlights
Since their discovery half a century ago, topologically closed packed (TCP) atomic structures [1,2] have been attracting the interest of academia and industries because of their corrosion resistance [3], superior hydrogen absorption [4], and excellent high-temperature creep resistance [5]
The inherent brittleness of TCP phase-based materials prevents them from having wider applications in industries
The brittleness of TCP phases originates from their close-packed complex atomic structure [6], which makes dislocation nucleation/movement very difficult [7]
Summary
Since their discovery half a century ago, topologically closed packed (TCP) atomic structures [1,2] have been attracting the interest of academia and industries because of their corrosion resistance [3], superior hydrogen absorption [4], and excellent high-temperature creep resistance [5]. Because of their exceptional mechanical properties at high temperature, TCP phase materials have been considered competent candidates for the industrial/structural application at the elevated temperature condition, such as nuclear reactor components and spaceship engines.
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