ANALYSIS OF PHASE FORMATION PROCESSES IN COMPLEX ALLOYS
Abstract
The study focuses on the phase formation processes in heat-resistant nickel alloys, which are critically important for the aviation and energy industries. These alloys operate under extreme conditions of high temperatures (up to 1373K) and mechanical stresses, particularly in turbine blades of aircraft engines, where exceptional strength and durability are required.In multicomponent systems, the interaction of numerous elements leads to the formation of solid solutions (γ-matrix), intermetallic compounds (γ'-phase), carbides (MC, M23C6), borides (M3B2), and oxide films. Thermodynamic principles, particularly Gibbs free energy minimization, determine the stability of these phases, while kinetic factors, such as atomic diffusion, influence their formation rate.The main phases in nickel alloys include: γ-matrix – a solid solution based on nickel with a face-centered cubic structure, ensuring plasticity; γ'-phase (Ni3(Al, Ta)) – an intermetallic compound occupying up to 70% of the alloy volume in materials like CMSX-4 and serving as the primary strengthening phase; сarbides, which enhance wear resistance; borides, which strengthen grain boundaries; oxide films, which protect against oxidation and reduce its rate by 30–40% at 1373K.Each alloying element plays a specific role: nickel forms the base; aluminum and tantalum contribute to γ'-phase formation; chromium, molybdenum, and tungsten promote carbide formation; boron strengthens grain boundaries; rhenium and ruthenium slow diffusion, increasing creep resistance; rare-earth elements (Ce, Y, La, Nd) form protective oxide films, improving heat resistance.Heat treatment optimizes the γ'-phase particle size (30–40 nm), increasing strength by 10–15%. Adjusting the alloy composition ensures phase balance, preventing harmful topologically close-packed phases, such as the σ-phase. Cooling rate control affects element segregation, and diffusion management, particularly using rhenium, which slows diffusion by 20–30%, enhances durability (Rhenium effect).
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