The three-dimensional (3D) atom-probe technique produces a reconstruction of the elemental chemical identities and three-dimensional positions of atoms field evaporated from a sharply pointed metal specimen, with a local radius of curvature of less than 50 nm. The number of atoms collected can be on the order of one million, representing an analysis volume of approximately 20 nm x 20 nm x 200 nm (80,000 nm(3)). This large amount of data allows for the identification of microstructural features in a sample, such as grain or heterophase boundaries, if the feature density is large enough. Correlation of the measured atomic positions with these identified features results in an atom-by-atom description of the chemical environment of crystallographic defects. This article outlines a data compilation technique for the generation of composition profiles in the vicinity of interfaces in a geometrically independent way. This approach is applied to quantitative determination of interfacial segregation of silver at a MgO/Cu(Ag) heterophase interface.

/pdf/analysis-of-three-dimensional-atom-probe-data-by-the-2win7bl4nm.pdf

Analysis of Three-dimensional Atom-probe Data by the Proximity Histogram

The effect of lattice misfit on the dislocation motion in superalloys during high-temperature low-stress creep

An experimental analysis of the γ ↔ γ + γ ′ phase transformations in two single-crystal Nickel-based superalloys is presented. The transformations are characterised macroscopically by differential thermal analysis and dilatometry measurements and microscopically by qualitative and quantitative metallography of samples quenched during various thermal cycles. This fully covers the large changes in precipitate morphology and volume fraction encountered in the upper temperature transformation domain (between 1100 and 1300°C). It is shown that dissolution and precipitation processes are strongly influenced by the local elastic distortions resulting from the lattice mismatch between the two phases. The complex microstructure evolution observed is explained by considering the successive equilibrium shapes of a coherent precipitate growing in more or less strong interaction with its neighbors.

Precipitation and dissolution processes in γ/γ′ single crystal nickel-based superalloys

Kinetics of the topological inversion of the γ/γ'-microstructure during creep of a nickel-based superalloy

Multimodal size distributions of γ′ precipitates during continuous cooling of UDIMET 720 Li

γ′ Precipitate splitting in Nickel-based superalloys: A 3-D finite element analysis

Chemically oriented γ′ plate development in a nickel base superalloy

A model for low stress cross-diffusional creep and directional coarsening of superalloys

From the first forged turbine blades made of iron base alloys to the present nickel base single-grain
turbine blades and vanes manufactured by directional solidification, an enormous amount of research
has been directed to attaining the hottest possible combustion chamber temperatures in jet engines
Temperature has been increased by about 15 K each year for the last two decades, improving the
thermodynamic efficiency of the engines The more recent developments concern the manufacturing
of single-grain parts made of nickel base superalloys with large amount of the γ ′ hardening phaseThis paper first presents the directional solidification process used to produce single-grain parts, the
formation of as-cast microstructures and the defects that can arise during solidification In the second
part the thermal treatments that are applied to the nickel base superalloys in order to enhance their
mechanical properties are detailed The effect of crystallographic orientation and of the γ / γ ′
microstructure on the mechanical properties is briefly presented, as well as the microstructural
changes that can possibly arise during service

/pdf/directionally-solidified-materials-nickel-base-superalloys-1w888jfvoo.pdf

Directionally Solidified Materials:Nickel-base Superalloys forGas Turbines

Cet article presente les resultats de l'analyse par sonde atomique des interfaces γ/γ' dans un superalliage monocristallin a base de nickel flue pendant 5 h a 1050 °C, sous une charge uniaxiale de compression de 100 MPa appliquee selon un axe (001). Des variations subtiles de composition sont detectees entre les deux types d'interfaces, paralleles ou perpendiculaires a la direction de la charge. Elles sont interpretees comme les premices de l'evolution morphologique des precipites conduisant a la mise en radeaux. La force motrice qui regit la migration des especes chimiques est discutee grâce a la connaissance du champ de contraintes local obtenu par un calcul aux elements finis.

https://mmm.edpsciences.org/articles/mmm/pdf/1996/03/mmm_1996__7_3_185_0.pdf

Alain Hazotte

Papers

γ′ Precipitate splitting in Nickel-based superalloys: A 3-D finite element analysis

Chemically oriented γ′ plate development in a nickel base superalloy

A model for low stress cross-diffusional creep and directional coarsening of superalloys

Directionally Solidified Materials:Nickel-base Superalloys forGas Turbines

Concentration gradients near heterophase boundaries in crept single crystal nickel base superalloys