N. E. Dmitrieva

Investigation of the Phase Diagram and the Determination of Synthesis Conditions of Volume Amorphous Alloys in the Cu-Ni-Zr System at 1123 K

The phase equilibria in the Cu-Ni-Zr system in a field enriched by zirconium at 1123 K were investigated by the methods of X-ray and electron-probe microanalysis, microdurometry, and scanning calorimetry. A fragment of the isothermal section of the given system was constructed and the borders of areas of homogeneity of double phases of the Ni-Zr and Cu-Zr systems were defined. It was established that the double compounds NiZr and NiZr2 dissolve up to 33 and 12 at % Cu, respectively, and CuZr and CuZr2, dissolve up to 7 at % Ni.

Phase equilibria in Cu-Al-Zr system at 1073 K and aluminum concentration of less than 55 at %

X-ray diffraction and electron probe microanalysis were used to investigate phase equilibria in the ternary Cu-Al-Zr system at 1073 K in the Zr-rich region. The fragment of the isothermal section of the system was plotted. The regions of homogeneity of the ternary ZrCu2Al and ZrCuxAl2 − x phases were investigated. The type of phase equilibria between binary and ternary compounds of the Al-Cu-Zr system was established. It was found out that, at a Zr concentration above 55 at %, ternary compounds are not formed, and the Zr3Al and Zr2Cu phases were in equilibria with α-Zr at 1073 K.

Phase equilibria in Al-Ni-Zr system at 1123 K

Phase equilibria in ternary Al-Ni-Zr system have been studied using X-ray phase and electron probe microanalyses at 1123 K in the content range of 0–45 at % Al. A fragment of the isothermal section of this system has been plotted. The existence of three-phase equilibria Zr7Ni10 + Zr8Ni21 + Zr2Ni7, τ2-ZrNi2Al + NiAl + Zr2Ni7, NiAl + Ni3Al + Zr2Ni7, Zr7Ni10 + Zr2Ni7 + τ2-ZrNi2Al at 1123 K has been established for the first time. Phase based of binary compound Zr2Ni7 dissolves up to 13 at % aluminum. The crystalline structure of the τ7-Zr5Ni4Al phase has been determined, including structure type U3Si2, spatial group P4/mbm (a = 7.1852(7) Å, c = 3.3019(5) Å).

Interaction of aluminum with chromium and zirconium under equilibrium and non-equilibrium conditions

Crystallization processes in the aluminum-rich region of the ternary Al-Cr-Zr system were studied via the complex of the methods of physical and chemical analysis. It was found that in the equilibrium crystallization of these alloys along the Cr: Zr = 14: 5 section, aluminum and the CrAl7 intermetallic compound are crystallized, whereas under non-equilibrium conditions at quenching rates of 106 degree s−1, ZrAl3 phase and aluminum-based supersaturated solid solution are formed.

α- and β-phases of the Al-Mn-Si system

Homogeneity regions and crystal structures of ternary α- and β-phases based on Al9Mn2Si and Al9Mn3Si have been investigated at a temperature of 823 K by scanning electron microscopy, X-ray, and electron probe microanalysis techniques. It is established that the α-phase is formed in the composition region of 7.4–15.9 at % of Si at a manganese isoconcentrate of ∼18 at %. When the manganese concentration is 24–26%, the β-phase has a homogeneity region from 3.7 to 18.5 at % of Si and is situated parallel to the Al-Si side. A fragment of the isothermal section for the Al-Mn-Si system in an aluminum-rich alloy region has been constructed.

Determining the boundaries of second-type phase transitions in Ag–Mg–Cd alloys by means of diffusion couples

The interaction between elements in the transition zones of diffusion couples Mg + AgCd–alloy are studied. Isothermal sections of the Ag–Mg–Cd ternary system at 573 K are constructed. The existence of a Heusler phase based on H–Ag2MgCd compound is found in the field of the solid β′-solution. It is shown that the interdiffusion of components prevents the formation of ordered phases in the transition zones of bimetals, allowing us to determine the boundaries of second-type phase transitions in solid solutions.

Phase transformations in rapidly quenched Al–Cr–Zr alloys during heat treatment

Results from studying the effect zirconium has on solid-phase processes in aluminum–chromium alloys are presented. Rapidly quenched alloys are prepared via melt spinning. The quenching rate is ~106 K/s. By means of physicochemical analysis, it is shown that doping Al–Cr alloys with zirconium improves the thermal stability of supersaturated solid solutions and stabilizes their microcrystalline structure; this hinders the coagulation of intermetallic phases and thus improves the hardness of the alloys. It is found that supersaturated solid solutions of Cr and Zr in aluminum undergo stepwise decomposition; the temperature and time parameters of each step are shown in TTT diagrams.

Comparison of corrosion properties of equilibrium and fast-quenched Al-Fe-V alloys in chloride-containing solution

This article discusses the results of an investigation of the corrosion properties of fast-quenched and equilibrium alloys based on aluminum quenched with iron and vanadium. It has been demonstrated that the corrosion properties of the considered systems deteriorate with an increase of content of dopants, as well as with transition of alloys from a fast-quenched to equilibrium state. The observed effects are probably related to the deposition of new phases, which occur in an increase in content of dopant, as well as a result of thermal processing. The consequence of these processes is an increase in the total surface area of phase boundaries, which are the predominant locations of corrosion destructions.

Interaction of aluminum with niobium and scandium in equilibrium and nonequilibrium states

It was established by a complex of physicochemical methods that are only phase based on the binary intermetallics ScAl3 and NbAl3, containing neglible amount of doping additives, are found in in the system Al-Nb-Sc in equilibrium with aluminum. Aluminum and binary phases ScAl3 and NbAl3 come into eutectic equilibrium at 873 K. Joint doping of aluminum with niobium and scandium leads to a decrease in the extension of the range of a supersaturated solid solution based on aluminum.

Phase equilibria in the Al-Ni-Cu-Zr quaternary system at 1123 K and a zirconium concentration higher than 30 atomic percent

The phase equilibria in the Al-Ni-Cu-Zr quaternary system at 1123 K and a concentration of Zr higher than 30 at % have been determined using the methods of X-ray phase analysis, X-ray spectral microanalysis, scanning electron microscopy, and differential scanning calorimetry. An area of the existence of a quaternary liquid phase with a melting point of 1110 K at the concentrations of copper and zirconium equal to 15.1 and 58.0 at %, respectively, was detected in the system. The concentrations of other components vary in the range from 13.4 to 19.5 for Al and from 7.4 to 13.5 at % for Ni. For the first time, the existence of seven four-phase equilibria was determined experimentally.