A powder metallurgy nickel-based superalloy EP962NP was subjected to solid solution treated and cooled in four media (water, oil, air and furnace) followed by aging treatment to investigate the correlation between secondary γ′ (γs′) and tensile properties of the experimental alloy at 750 °C. Results show that the size of γs′ increases sharply with the decreasing cooling rate, and morphologies of γs′ depend on the cooling regime and present various characteristics including spherical, rod-shaped, cubic, etc. By implementing the heat treatment process of solid solution treatment (1210 °C/2 h, air cooling/AC) and two-step aging treatment (i.e., 870 °C/8 h, AC + 760 °C/16 h, AC), superior comprehensive mechanical properties can be obtained with ultimate tensile strength, yield strength and elongation of 1251 MPa, 1079 MPa and 13.3%, respectively, due to the high density of stacking faults. Interaction between γ′ and dislocations indicates that the deformation mechanism of the alloy exhibits stacking faults on (1‾11‾) [121] and microtwins, which depends on the size of γs′. The increasing size of γs′ precipitates drives a transition in the dominant deformation mechanism from stacking faults shearing to microtwinning.

The adiabatic stiffness constants Cik of binary and ternary Fe3AlxSiy alloys, 0 ⩽ x,y ⩽ 1.3, 0.6 ⩽ x + y ⩽ 1.3 have been measured in the temperature range 90–360 K. The stiffnesses were derived from the velocities at which ultrasonic pulses propagated in single crystals. Prior to the measurements of the Cik, the specimens had been quenched from successively lower temperatures: 1273, 1073 and 723 K. According to the current phase diagrams, the state of order of most of the present binary alloys changes in the quoted temperature range. In most cases this affects the Cik. For binary FeAl alloys there is a strong ΔE effect. From the stiffnesses, the dislocation line energies and tensions have been calculated within the framework of the linear anisotropic theory of elasticity.

The adiabatic stiffness constants Cik of four nickel-base alloys are determined in the temperature range 90 to 360 K: stoichiometric Ni3Al, γ′-105, γ′-PE16, NIMONIC 105. γ′-105 and γ′-PE16 are the γ-phases in the commercial superalloys NIMONIC 105 and NIMONIC PE16, respectively. The intermetallic compounds Ni3Al, γ′-105, and γ′-PE16 have the Ll2-crystal structure. The stiffness Cik is derived from the velocities at which ultrasonic pulses propagate along 〈110〉 directions in single crystals. The room-temperature stiffnes of Ni3Al is in excellent agreement with that published by Kayser and Stassis. For all four alloys the dislocation line energies and tensions of edge and screw dislocations are calculated within the framework of anisotropic theory of elasticity. Die adiabatischen elastischen Moduln Cik von vier Nickel-Basis-Legierungen werden im Temperaturbereich 90 bis 360 K bestimmt: stöchimetrisches Ni3Al, γ′-105, γ′-PE16, NIMONIC 105. γ′-105 und γ′-PE16 sind die γ′-Phasen in den kommerziellen Superlegierungen NIMONIC 105 bzw. NIMONIC PE16. Die intermetallischen Verbindungen Ni3Al, γ′-105 und γ′-PE16 haben die Ll2-Kristallstruktur. Die Konstanten Cik werden aus den Geschwindigkeiten berechnet, mit denen sich Ultraschallimpulse längs 〈110〉-Richtungen ausbreiten. Bei Raumtemperatur stimmen die gefundenen Konstanten sehr gut mit den von Kayser und Stassis publizierten überein. Für alle vier Legierungen werden die Versetzungslinienenergien und -spannungen im Rahmen linearer, anisotroper Elastizitätstheorie berechnet.