Direct observations of nucleation in a nondilute multicomponent alloy
نویسندگان
چکیده
The chemical pathways leading to L12 nucleation from nondilute Ni-5.2 Al-14.2 Cr at. %, fcc , at 873 K are followed with radial distribution functions and isoconcentration surface analyses of direct-space atom-probe tomographic images. Although Cr atoms initially are randomly distributed, a distribution of congruent Ni3Al short-range-order domains SRO , R 0.6 nm, results from Al diffusion during quenching. Domain site occupancy develops as their number density increases leading to Al-rich phase separation by -nucleation, R =0.75 nm, after SRO occurs.
منابع مشابه
KINETICS OF -Fe NANOCRYSTALLIZATION IN Fe55Cr18Mo7B16C4 BULK AMORPHOUS ALLOY
Abstract: In this research work, crystallization kinetics of Fe55Cr18Mo7B16C4 alloy was evaluated by X-ray diffraction, TEM observations and differential scanning calorimetric tests. In practice, crystallization and growth mechanisms were investigated using DSC tests in four different heating rates. Results showed that a two -step crystallization process occurred in the alloy in which - Fe phas...
متن کاملNANOCRYSTALLIZATION MECHANISMS OF Fe52Cr18Mo7B16C4Nb3 BULK AMORPHOUS STEEL
Crystallization kinetics of Fe52Cr18Mo7B16C4Nb3 alloy was evaluated using X-ray diffraction, differential scanning calorimetric (DSC) tests and TEM observations in this research work. In effect, crystallization and growth mechanisms were investigated using DSC tests in four different heating rates (10, 20, 30, 40 K/min) and kinetic models (i.e. Kissinger- Starink, Ozawa, and Matusita methods). ...
متن کاملA DETAILED STUDY TOWARD THE NANO -CRYSTALLIZATION OF α – Fe IN Fe55-X Cr18Mo7B16C4 BULK AMORPHOUS ALLOY
Crystallization of α – Fe phase during annealing process of Fe55Cr18Mo7B16C4 bulk amorphous alloy has been evaluated by X- ray diffraction, differential scanning calorimetric tests and TEM observations in this research. In effect, crystallization mechanism and activation energy of crystallization were evaluated using DSC tests in four different heating rates (10, 20, 30, 40 K/min). A two -st...
متن کاملThe mechanism of morphogenesis in a phase-separating concentrated multicomponent alloy.
What determines the morphology of a decomposing alloy? Besides the well-established effect of the nucleation barrier, we demonstrate that, in a concentrated multicomponent Ni(Al,Cr) alloy, the details of the diffusion mechanism strongly affect the kinetic pathway of precipitation. Our argument is based on the combined use of atomic-scale observations, using three-dimensional atom-probe tomograp...
متن کاملOn the interplay between tungsten and tantalum atoms in Ni-based superalloys: An atom-probe tomographic and first-principles study
The partitioning behavior of W in a multicomponent Ni-based superalloy and in a ternary Ni–Al–W alloy is investigated using atom-probe tomography APT and first-principles calculations. APT observations indicate that whereas W partitions preferentially to the L12 -precipitates in the ternary alloy, its partitioning behavior is reversed in favor of the fcc -matrix in the multicomponent alloy. Fir...
متن کامل