M.J. Blackburn

Characterization of the microstructure and phase equilibria calculations for the powder metallurgy superalloy IN100

The microstructure of the Ni-based superalloy IN100 processed by a powder metallurgy route was evaluated to reveal the structures, volume fractions, distributions, and chemistries of the various phases present. These data were compared with those predicted by computational thermodynamics. It is shown that the microstructural parameters expected on the basis of global equilibrium conditions differ significantly from those measured experimentally. However, modification of these calculations by use of constrained and successive equilibria compensated for kinetic effects and led to accurate (or better) predictions of phase volume fractions and chemistries in this alloy. This demonstrated that such modified phase equilibria calculations could be powerful tools for modeling microstructures, even in complex multicomponent alloys processed under nonequilibrium conditions.

Techniques for microstructural characterization of powder-processed nickel-based superalloys

Methods are described for sample preparation of polycrystalline Ni-based superalloys in order to perform a detailed microstructural characterization. Specific techniques for the precise definition of the various phases present are outlined and these are shown to be useful for the measurement of size, volume fractions and distribution. A number of optical, scanning and transmission microscopy techniques are used to provide the necessary information.

Crystallization of Glassy Powder from Aluminum-Rare Earth- Transition Metal Alloys

The microstructures exhibited by gas atomized powders of two alloys, Al-6Gd-6Ni-1Fe and Al-5Y-10Ni (at. %), have been analyzed using electron microscopy. It was found that the microstructure depends critically on the particle size obtained during atomization. Small particles ( 30μm) are often fully crystalline, consisting of fine interspersed Al and intermetallic grains.

Microstructure And Ternary Phases In Al-rich Al-Y-Ni Alloys.

The results of a transmission electron microscopy study on the crystal structures and morphologies exhibited by each of the phases in a set of four Al-rich Al-Y-Ni alloys which contain 1.7–4.5 at. % Y and 3.5–10.1 at. % Ni are presented. It is shown that each alloy contains fcc-Al, a binary Al 3 Ni or Al 3 Y phase (depending on alloy composition), and a ternary phase. The same ternary phase was found in each alloy and this was found to correspond to a new phase Al 19 Ni 5 Y 3 (Cmcm, a=0.4025 nm, b=0.799 nm and c= 2.689 nm, Al 19 Ni 5 Gd 3 structure type). In many cases, the ternary particles also contain embedded slabs of the equilibrium Al 23 Ni 6 Y 4 phase. This phase mixture did not decompose even after extended annealing.