Performance analysis of Mo(Si, Al)2 solid solutions based on valence electron structure

Abstract

In the present study, the valence electron structures (VESs) of Mo(Si1-xAlx)2 solid solution alloys were calculated according to the empirical electron theory (EET) of solids and molecules, and the relationship between VESs and their properties was determined. The results indicated that the hardness of the phases with the C11b crystal structure could be compared using the quantity of covalent electrons (CEs) and bonding energy on the strongest bonds, the strength by the ratio of the quantity of CEs to the total quantity of valence electrons, and the plasticity by the quantity of lattice electrons (LEs). It was found that the dissolution of Al in the MoSi2 phase could reduce the quantity of CEs, bonding energy, percentage of the total quantity of CEs relative to the total quantity of valence electrons and increase the quantity of LEs in Mo(Si1-xAlx)2 alloyed materials. These results indicated that alloying Al with MoSi2 would decrease the hardness value (HV) and strength and increase the plasticity of Mo(Si1-xAlx)2 solid solutions. Based on these results, samples of Mo(Si1-xAlx)2 solid solutions were prepared; when the Al content reached 12 at%, the hardness and bending strength of Mo(Si1-xAlx)2 solid solutions decreased by 24.84% and 14.96%, respectively, and the fracture toughness increased by 119.94% compared to that of the unalloyed MoSi2.