Papers by Keyword: Intermetallides

Abstract: The article presents the results of obtaining complex-alloyed aluminum-zirconium alloys by aluminothermy of initial metal oxides. Aluminum-matrix Al-Zr-W alloys have been obtained by a metal-thermal reduction with an excessive amount of aluminum in the initial charge of zirconium and tungsten oxides. The process of synthesis is presented as partial reduction reactions of zirconium, tungsten and synthesis of intermetallic compounds. It is shown that thermodynamic parameters of the reactions are favorable for the process of formation of refractory metal alloys. It is found that the temperature reached during the melting process makes it possible to obtain intermetallids and to synthesize alloys at the out-of-furnace process in the form of a compact ingot. The composition of the alloys obtained has been determined by an X-ray phase and an element analysis. It is established that the alloys have a composite structure: intermetallides Al₃Zr and Al₄W are distributed in the aluminum matrix.

Abstract: In this paper, the processes of forming the samples of powder materials based on the titanium – nickel and nickel – aluminium systems were investigated. The possibility of conducting self-propagating high-temperature synthesis (SHS) in the nickel – aluminium system without protective atmosphere is shown. The initial heating temperature of the starting mixture is the main factor determining the flow of this process. Its growth leads to an increase of the synthesis speed. The number of the oxides decreases at the same time. Thermodynamic calculations of the combustion reactions were performed under different conditions. Phase analysis has shown the presence of the intermetallic compounds, which correspond to the phase diagram of the nickel – aluminium system. Thermodynamic calculations confirmed the assumption of preferential oxidation of metallic sodium when it was added to the mixture of powders in the titanium – nickel system. Technological features of obtaining products of various functional purposes are justified. The performed research confirms the effectiveness and promising use of self-propagating high-temperature synthesis for the products fabrication by powder metallurgy methods.

Abstract: Simple model has been formulated to describe intermetallic formation in surface layers during ion implantation. The isothermal conditions have been assumed. The reaction scheme includes three stages (a) Ni+Al→NiAl (b) 3Ni+Al→Ni₃Al (c) Ni₃Al+2Al→3NiAl. The finiteness of relaxation time taking into consideration in the model leads to specific distributions of elements and new phases. The general approach is illustrated with the help of some example.