Konstantin A. Meleshevich

Phase Equilibria in the Mg – Al – Ca System (Region 50-100 mass% Mg)

Phase equilibria in the ternary system Mg – Al – Ca in the composition range 50-100 mass% Mg were studied by the methods of differential thermal, x‐ray diffraction, electron-probe and microscopic analysis. The projection of the liquidus surface on the concentration triangle, isothermal section at 150°C and polythermal sections at 4.5, 8.5, and 16 mass% Al were constructed. It was determined that additions of Al and Ca decrease the liquidus temperature of magnesium alloys (from 650 to 438°C). It is shown that the three-phase region + + exists at 150°C with the corresponding two-phase fields. The temperature dependence of the homogeneity range of the Mg‐based solid solution was determined, and also the temperatures of the phase transformations which occur in the investigated range of compositions in the system.

Alloy Constitution and Phase Equilibria in the Hf–Ru–Rh System. II. Liquidus Surface, Melting Diagram, and Vertical Sections of the Partial Hf–HfRu–HfRh System

According to the constitution of the solidus surface in the Hf–Ru–Rh system over the composition range 50−100 at.% Hf and the data obtained in studying the as-cast alloys by physicochemical analysis techniques, we constructed, for the first time, the liquidus surface of the partial Hf–HfRu–HfRh system on the composition triangle and its melting diagram. The vertical sections at 5 at.% Ru, 10 at.% Rh, and 75 and 80 at.% Hf at the ratio Ru : Rh = 1 : 1 are presented. The processes that occur when the alloys are crystallized are shown in the reaction scheme. The primary crystallization regions for a continuous series of solid solutions between isostructural (CsCl type) phases formed by the HfRu compound and its high-temperature modification (δ phase) as well as β-Hf and γ-Hf2Rh (Ti2Ni type) solid solutions are parts of the liquidus surface. An invariant four-phase equilibrium involving liquid, LU + δ ⇆ γ + , is observed at 1373°C in the system.

Phase Equilibria During Solidification in the Ti–TiAl–DyAl2–Dy Region of the Ti–Dy–Al System

Phase equilibria during solidification in the Ti–TiAl–DyAl2–Dy region of the Ti–Dy–Al system are studied by differential thermal analysis, X-ray diffraction, metallography, and electron microprobe analysis. The liquidus and solidus surfaces, vertical sections, and reaction scheme in the solidification range are presented. No ternary compounds are found in the studied composition range. It is shown that DyAl2 undergoes polymorphic transformation at ~1200°C. The αl and α2 phases that coexist only with solid phases in the binary Ti–Al system participate in equilibria with the liquid phase in the ternary Ti–Dy–Al system. The liquidus surface is characterized by the primary solidification fields of the phases based on βTi (β), high-temperature αTi (αh), lowtemperature αTi (αl), Ti3Al (α2), TiAl (γ), Dy2Al, Dy3Al2, DyAl, βDyAl2, αDyAl2, βDy, and αDy. The solidus surface has elven three-phase fields: β + (βDyAl2) + αl, (βDyAl2) + αl + α2, β + αh + (βDyAl2), αh + γ + (βDyAl2), (βDyAl2) + α2 + (αDyAl2), (DyAl) + (Dy3Al2) + (αDyAl2), (αDy) + β + αl, (DyAl2) + α2 + (Dy3Al2), (Dy3Al2) + α2 + (Dy2Al), α2 + αl + (Dy2Al), and αl + (αDy) + (Dy2Al). The first two fields result from invariant four-phase peritectic reactions, LP1 + β + (DyAl2) ⇄ αl and LP2 + αl + (βDyAl2) ⇄ α2 proceeding at 1130 ± 5°C and 1180 ± 7°C, respectively. The next eight three-phase fields result from invariant four-phase transition reactions: LU1 + β ⇄ αh + (βDyAl2) at 1325 ± 8°C, LU2 + αh ⇄ γ + (βDyAl2) at 1260°C, LU3 + (βDyAl2) ⇄ α2 + (αDyAl2) at 1060 ± 4°C, LU4 + (DyAl) ⇄ (Dy3Al2) + (αDyAl2) at 1010 ± 9°C, LU5 + (αDy) ⇄ β + αl at 970 ± 4°C, LU6 + (αDyAl2) ⇄ α2 + (Dy3Al2) at 960 ± 8°C, LU7 + (Dy3Al2) ⇄ α2 + (Dy2Al) at 955 ± 16°C, and LU8 + α2 ⇄ αl + (Dy2Al) at ~930°C. The three-phase αl + (αDy) + (Dy2Al) field results from an invariant eutectic process, LE ⇄ αl + (αDy) + (Dy2Al), at 910 ± 15°C. The two-phase region in the solidus surface has a temperature maximum at 1343 ± 5°C, corresponding to the invariant three-phase le1 ⇄ β + (βDyAl2) reaction.

The Constitution of Alloys and Phase Diagram of the Ternary Al–Cr–Pt System at 50–100 at.% Pt. I. Solidus Surface and Isothermal Section in the Al–Cr–Pt System at 1350 C in the Range 50–100 at.% Pt

The results of high-temperature diffraction, metallography, X-ray diffraction, electron microprobe analysis, and differential thermal analysis are used to specify the constitution of the Al–Pt system in the near-equiatomic range. The solidus surface is constructed for the first time on the composition triangle, and the constitution of the isothermal section at 1350°C in the range 50–100 at.% Pt of the Al–Cr–Pt ternary system is specified. The solidus surface consists of six single-phase surfaces corresponding to the ternary τ1 phase (unknown structure), solid solutions based on platinum, and four binary phases existing in the Al–Pt system; nine ruled surfaces bounding two-phase volumes; and four isothermal planes forming invariant four-phase equilibria with participation of a liquid phase. When temperature decreases from subsolidus to 1350°C, stability of the phase based on the <(Al, Cr)Pt2> compound (low-temperature modification) increases substantially. This phase takes part in equilibria with other intermediate phases and with the Pt-based solid solution.

Effect Of Formation Conditions of Thick Granular Films Based on Dispersed Co 3 b On Their Phase Composition and Magnetoresistance

An important scientific and technical problem on developing thick resistive granular films used in microelectronics and tool manufacturing is solved. Magnetoresistive Co-containing granular films are obtained by screen printing the pastes consisting of fine-grained cobalt boride Co3B and organic binder on a dielectric substrate. Then, the deposited films are heat treated in air with no protection at all. Differential thermal analysis and thermogravimetric analysis reveal that only ferromagnetic Co (FCC) and amorphous B2O3 are present in the structure of the films at T = 650–850°C. On this basis, the modes for the heat treatment of films are developed. The effect of magnetic field on the electrical resistance of films is studied.

Phase Equilibria in the Ti–Ti5Si3–Dy5Si3–Dy Region of the Ti–Dy–Si System

Differential thermal analysis, X-ray diffraction, and metallography are employed to examine the phase equilibria in the Ti–Ti5Si3–Dy5Si3–Dy region of the Ti–Dy–Si system. Isothermal sections at 1100 and 900°C, vertical sections at 5Si, 65Ti, and 65Dy isopleths, and a reaction scheme are constructed. The ternary compound TiDySi (τ) exists at experimental temperatures and has no appreciable homogeneity range. The isothermal sections at 1100 and 900°C are similar and characterized by five three-phase regions (β + (α-Dy) + τ, β + (Ti3Si) + τ, (Ti3Si) + τ + (Ti5Si3), (α-Dy) + τ + (Dy5Si3), and (Ti5Si3) + τ + (Dy5Si3)) and respective two-phase fields. Three invariant four-phase equilibria are found in solid state: β + (Ti5Si3) ⇄ (Ti3Si) + τ (U3), β + τ + (Ti3Si) ⇄ α (P2), and β + τ + (α-Dy) ⇄ α (P3) at ~1150, 900, and 885°C, respectively. There is also a threephase equilibrium, β + τ ⇄ α, at 845°C (p4). The phase equilibria are summarized in the reaction scheme.