Papers by Author: Dmytro Kevorkov

Abstract: The phase relationship of the Mg-Ni-Y system along the Mg-NiY line has been investigated using electron probe micro analysis (EPMA) at 673 K. Three two phase regions (Mg₂Y+τ₆, Mg₂Y+ MgNiY(τ₃), MgY+Mg₃Ni₂Y₄(τ₁)) and two three phase regions (Mg₂Y+Mg₃Ni₂Y₄(τ₁)+ MgNi₂Y₂(τ₂) and NiY+Mg₃Ni₂Y₄(τ₁)+MgNi₂Y₂(τ₂)) have been identified. One new ternary compound Mg₅NiY(τ₅) was found and reported for the first time. Ternary solubility of the Mg_8-13NiY(τ₆) compound has been established which extends from 77.10 at.% Mg until 86.77 at.% Mg along the Mg-NiY section. Solubility of the third element in the binary compounds, NiY, Mg₂Y and MgY has also been determined. Keywords: Mg alloy, phase identification, phase equilibrium, isothermal section.

Abstract: In this work, the partial isothermal section of the Al-Ca-Zn system in the region between 33.3 and 100 at.% Ca has been investigated at 350°C using key alloys. The actual composition of the alloys is measured by inductively coupled plasma technique. Phase relations and solubility limits of the binary and ternary compounds have been determined by means of electron probe microanalysis and X-ray diffraction. In the current work, a new ternary compound has been identified in this region with the Al₉Ca₃₁Zn₁₀ (IM1) composition. Binary compound Al₁₄Ca₁₃ (IM2) has an extended solid solubility into the ternary system. The homogeneity ranges of the Al₂Ca, the MgNi₂-type C36 phase Al_2-xCaZn_x (0.28≤x≤0.70) (IM3) at 350°C and CaZn₂ compounds in the pseudobinary Al₂Ca-CaZn₂ section have been determined at 350°C and the results are combined with the literature to construct the partial vertical Al₂Ca-CaZn₂ section and partial isothermal Al-Ca-Zn section at 350°C.

Abstract: In the present research, seven multi-phase diffusion couples, with terminal alloys having different microstructural features, were prepared and annealed for 4 weeks at 335°C. The phase relations and change of morphological characteristics of each phase were studied along the diffusion zone by means of scanning electron microscopy/energy dispersive X-ray spectroscopy and quantitative electron probe microanalysis. Depending on the different terminal compositions of the diffusion couples, the morphological evolution in the diffusion zone can be: tooth-like, matrix phase with isolated and/or dendritic precipitates. Electron back-scattered diffraction analysis was carried out to investigate the crystal orientation of the ternary compounds and the crystal orientation relations at the interface of the diffusion zones.