Physicochemical Investigation of the Reaction of Components of the Si — Al — O — N — Ti System in the Si3N4 — Al2O3 — AlN — SiO2 — TiN — TiO2 Region. Part 2. Subsystems Si3N4 — AlN,TiN — AlN,Al2O3 — AlN

The reaction of components of the Si — Al — O — N — Ti system in its elements Si ₃N₄ — AlN, TiN — AlN, and Al ₂O ₃ — AlN was investigated by differential thermal and x-ray diffraction analysis. It was established that upon hot pressing mixtures of Si₃N ₄ and AlN (up to 1950°C) free silicon is formed by the decomposition of Si ₃N₄, which reacts with oxygen present as an impurity to form SiO. When TiN reacts with AlN a phase with the spinel structure (Al₂₃O ₂₇N ₅), which can form only in the presence of excess oxygen, appears in addition to the initial components. Spinel is also produced by the reaction of Al ₂O₃ with AlN. In this case a eutectic between Al ₂₃O₂₇N₅ and Al₂O₃ is observed.     

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, xray 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 + 2Ca> + 17Al₁₂> exists at 150°C with the corresponding two-phase fields. The temperature dependence of the homogeneity range of the Mgbased solid solution was determined, and also the temperatures of the phase transformations which occur in the investigated range of compositions in the system.     

Phase equilibria in the α-Ti-Al-Si region of the Ti-Si-Al system

An experimental investigation of the phase relations in the titanium (Ti)-aluminum (Al)-silicon (Si) system was undertaken by differential thermal analysis, x-ray diffraction, metallography, and microprobe analysis. The present measurements when combined with those from an earlier investigation at this laboratory provide data for 56 alloy compositions in the Ti-Al-Si system. The combined results allowed the construction of a solidus projection, a melting diagram including both solidus and liquidus, partial isothermal sections at 1270 °C and 1250 °C, three isopleths with a constant percentage of one or another component, and a reaction scheme.     

Physicochemical Interactions in Systems Formed by Trivalent REM with Group IVp Elements. Part 2. Phase Diagrams

A major aspect is considered of the physicochemical interaction in binary systems formed by REM with group IV p elements, namely the phase diagrams. The general regularities and the differences between these phase diagrams are considered for REM – X systems (X = Si, Ge, Sn, and Pb), particularly the relationship between the phase diagram topology and the crystallochemistry of the compounds formed. A comparison is performed for predicted and experimentally constructed phase diagrams.     

Structure and properties of as-cast Ti-Dy alloys

A prediction of the Ti-Dy phase diagram was given, according to which the system is of eutectic type with the eutectic coordinates 1270 °C and 82 at.% Dy. Experimental verification on the two key-alloys confirmed the type of system, as well as the eutectic coordinates. The last were established to be 1280 °C and 82 at.% Dy. The eutectic is fine with a grain size of about 0.2 μm. The hypo-eutectic alloy 95Ti-5Dy showed high plasticity at contraction that is on the level of pure titanium. The Ti-Dy system is proposed as a basis of composite materials of eutectic type.