Фазовый состав и микроструктура доэвтектических сплавов Mo-Si-V, полученных в условиях неравновесной кристаллизации

Abstract

The phase composition, microstructure are investigated and the densities of Mo-15.3Si (at. %) hypoeutectic alloys alloyed with vanadium are determined. The main phase components of the alloys and their volumetric contents were determined by X-ray phase analysis (XRD) and X-ray microanalysis (RSMA) methods. The unit cell parameters of the main phases of Mo-Si-V alloys are calculated. It is shown that with the introduction of up to 20.0 at. % of vanadium into the hypoeutectic alloy Mo-15.3Si, a structure is formed consisting of two solid solutions: (Mo,V)ss with silicon dissolved in it (up to 5.0 at. %) and (Mo,V)3Si with a silicon deficiency of about 4.0 at. % trelative to the stoichiometric composition. With an increase in the content of vanadium in alloys, the volume ratio of the metal component to the silicide ratio almost doubles. At the same time, the microhardness of the metal phase increases 1.5 times and reaches 887 HV, and the microhardness of silicide, on the contrary, decreases by 1.2 times and is 1057 HV. The dependences of the microhardness of the structural components of the alloys, as well as the parameters of their crystal lattices on the concentration of the alloying element in them, are consistent with the concepts of the formation of substitution solid solutions, both in the metal and in the silicide phases. The introduction of 20.0 at. % of vanadium into the Mo-15.3Si hypoeutectic alloy reduces its density, and, therefore, the mass of the alloy by 10.5% from 9.49 to 8.49 g/cm3.