Micro-mechanisms and precipitation kinetics of delta (δ) phase in Inconel 718 superalloy during aging
| Autor: | Hamed Mirzadeh, Mohsen Rafiei, Mehdi Malekan |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Precipitation (chemistry) Mechanical Engineering Diffusion Kinetics Metals and Alloys Thermodynamics 02 engineering and technology Activation energy 010402 general chemistry 021001 nanoscience & nanotechnology Kinetic energy 01 natural sciences 0104 chemical sciences Superalloy Mechanics of Materials Phase (matter) Materials Chemistry 0210 nano-technology Inconel |
| Zdroj: | Journal of Alloys and Compounds. 795:207-212 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/j.jallcom.2019.05.001 |
| Popis: | The formation of δ phase in Inconel 718 superalloy during aging was quantitatively studied based on improved analyzing techniques to unambiguously determine the mechanism of δ phase precipitation and its kinetics. Based on the general transformation rate expressed in terms of the time corresponding to the transformed fraction of 0.5 or 50% and also the modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation, the average activation energy for the formation of δ phase was determined as 212.4 kJ/mol and 197.5 kJ/mol, respectively. These values are comparable to the activation energy for diffusion of Nb in Ni (202.59 ± 4.71 kJ/mol). Therefore, the micro-mechanism for the formation of δ phase was characterized as the diffusion of Nb in the matrix. Based on the kinetic studies, the temperature of 1055.7 K (782.7 °C) was found as the lower bound for the formation of δ phase, which was consistent with the precipitation-temperature-time (PTT) plot developed for this material. Finally, a formula was obtained to quantitatively show the effects of aging temperature and cold rolling reduction on the transformation rate for the precipitation of δ phase. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect