Papers by Keyword: A-286 Alloy

Abstract: The influence of initial soaking and parameters of plastic deformation on the deformability of A-286 superalloy have been presented. The hot-torsion tests were executed at constant strain rates of 0.1 and 1.0 s^-1, at testing temperatures in the range 900-1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of flow stresses and strain limits. Activation energy for hot working Q was assessed for the alloy after two variants of previous heating, i.e. 1100°C/2 h and 1150°C/2 h.

Abstract: The influence of prolonged aging on the precipitation process of intermetallic phases, as well as carbide and boride in an Fe-Ni superalloy has been studied. The samples were subjected to a solution heat treatment at 980°C for 2 h and water quenched, and then aged at 715, 750 and 780°C for 0.5-500 h. The samples were analysed using transmission electron microscopy (TEM) and X-ray diffraction. Direct measurements on the electron micrographs allowed to calculate the mean diameter () of the γ’ phase. The growth step of the γ’ phase particles has been analysed on the basis of the LSW theory, as well as the activation energy of the γ’ phase coagulation has been estimated.

Abstract: The influence of prolonged ageing on the precipitation process of the secondary phases in an Fe-Ni superalloy of A-286 type has been studied. The samples were subjected to a solution heat treatment at 980°C for 2 h and water quenched, and then aged at temperatures of 715, 750 and 780°C at holding times from 0.5 to 500 h. Structural investigations were conducted using TEM and X-ray diffraction methods. The X-ray phase analyses performed on the isolates were obtained by anodic dissolution of the solid samples. After solution heat treatment the alloy has the structure of twinned austenite with a small amount of undissolved precipitates, such as carbide TiC, carbonitride TiC_0.3N_0.7, nitride TiN_0.3, carbosulfide Ti₄C₂S₂, Laves phase Ni₂Si, and boride MoB. The application of ageing causes precipitation processes of γ-Ni₃(Al,Ti), G (Ni₁₆Ti₆Si₇), η (Ni₃Ti), β (NiTi) and σ (Cr_0.46Mo_0.40Si_0.14) intermetallic phases, as well as the carbide M₂₃C₆. It was found that the main phase precipitating during alloy ageing was the γ intermetallic phase.

Abstract: The influence of prolonged ageing on the kinetics of the precipitation process of the secondary phases in an A-286 type Fe-Ni superalloy has been studied. The samples were subjected to a solution heat treatment at 980°C for 2 h and water quenched, and then aged at temperatures of 715, 750 and 780°C at holding times from 0.5 to 500 h. Structural investigations were conducted using X-ray diffraction methods. The values of the austenite lattice constant were estimated with the use of the cos²θ extrapolation function, and by the Toraya (WPPF) and Rietveld methods. It was found that the largest decrease in the austenite lattice constant took place during the initial period of ageing at all investigated temperatures, which corresponds to the spinodal decomposition of supersaturated austenite and formation of the γ'-Ni₃(Al,Ti) intermetallic phase. Good agreement between the values of the austenite lattice constant determined using the extrapolation function and the Rietveld method was found.

Abstract: The paper presents the results of research concerning the influence of hot deformation parameters on the structure and substructure as well as the plastic properties of a Fe–Ni austenitic alloy. The research was performed on a torsion plastometer in the range of temperatures of 900÷1150°C, at a strain rate 0.1 and 1.0 s-1. Plastic flow curves have been drawn up and the interrelations have been determined between the process parameters and the recrystallized grain size, inhomogeneity and shape. Functional relations between the Zener-Hollomon parameter and the mean grain size after dynamic recrystallization have been developed and the hot deformation activation energy has been estimated. The examination of substructure on TEM allowed the calculation of structural parameters: the average subgrain area and the mean dislocation density. A detailed investigation has shown that the substructure is inhomogeneous, consists of dense dislocation walls, subgrains and recrystallized regions.