Phase composition of heat-resisting alloy modified by ageing and alloyed by rhenium

• Main Authors: Koneva, Nina, Nikonenko, Elena, Popova, Natalya, Gibert, Ivan, Kozlov, Eduard
• Format: Conference Proceeding
• Language: English
• Subjects: Aging (metallurgy); Alloying elements; Aluminum; Annealing; Chromium; Crystallization; Crystallography; Heat resistant alloys; Heat treatment; Microstructure; Molybdenum; Morphology; Nickel base alloys; Phase composition; Qualitative analysis; Quantitative analysis; Rhenium; Sigma phase; Superalloys; Titanium; Transmission electron microscopy; Tungsten
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4966389

The paper presents the transmission electron microscope (TEM) investigations of the structure of Ni-Al-Cr-based superalloy which is obtained by directional crystallization technique. The structural TEM investigations are carried out in two stages: 1) annealing at 1150°C for 1 h and 2) annealing at 1100°C for 480 h. The qualitative and quantitative analysis is given for the structure, phase composition and morphology of heat-resisting alloy additionally alloyed by rhenium Re both in the original state and after thermal treatment. The heat-resisting alloy comprises ∼70 at % Ni, ∼17 at % Al and ∼5 at % Cr. The total amount of the primary alloying elements of Mo, W, Ta, Ti, Co, La was ∼7 at % and 0.4 at % Re. It is shown that the structure of the superalloy is represented by (γ + γ′)-phase mixture which has a morphologically correct crystallographic orientation and quasi-monocrystalline structure. σ-phase is formed in this superalloy due to rhenium. Since Re distribution in the alloy is not uniform, only a part of (γ + γ′)-phase quasi-cuboids is distorted. It is shown that Re modification distorts the ideal structure of (γ + γ′)-phase quasi-cuboids and results in the formation of β-, χ-and σ-phases.