Abstract
Molybdenum silicides are attractive high-temperature structural materials because of their excellent thermal stability and outstanding oxidation resistance at high temperatures. First-principles calculations were employed to investigate the effect of alloying elements (Cr, Nb, V, W, Al, Ga, and Ge) on the mechanical properties of Mo3Si. The structural stabilities of doped Mo3Si were calculated, showing that the Pm-3n structure was stable at the investigated low-doping concentration. The calculated elastic constants have also evaluated some essential mechanical properties of doped Mo3Si. Cr- and V-doping decreased the elastic modulus, while Al- and Nb-doping slightly increased the shear and Young’s modulus of Mo3Si. Furthermore, V-, Al- and Nb-doping decreased the B/G and Poisson ratio, suggesting that these elements could form strong covalent bonds, and decrease shear deformation and alloy ductility. Based on the three-dimensional contours and two-dimensional projection of the elastic modulus, Cr- and V-doping exhibited a significant influence on the anisotropy of the shear and Young’s modulus. According to charge density and density of states, the electronic structures of alloyed Mo3Si were further analyzed to reveal the doping effects.
Highlights
Molybdenum silicides are attractive high-temperature structural materials because of their excellent thermal stability and outstanding oxidation resistance at high temperatures [1,2,3,4,5,6]
It is of great significance to assess the structural stability for a doped system [18,19]
There are some small changes in density of states (DOS) with different doped elements
Summary
Molybdenum silicides are attractive high-temperature structural materials because of their excellent thermal stability and outstanding oxidation resistance at high temperatures [1,2,3,4,5,6]. Their brittleness at room temperature has restricted their engineering applications incredibly. For the Mo-Si system, there are three stable compounds: MoSi2 , Mo5 Si3 , and Mo3 Si. Notably, some studies [1,2,3,4] have focused on Mo5 Si3 and MoSi2 over the past few decades, while the research about Mo3 Si (another molybdenum silicide) is still limited, attributed to its relatively low fracture toughness and room temperature strength. The low fracture toughness of Mo3 Si is ascribed to its few active slip systems [7].
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