| |
Simonovic, D., & Sluiter, M. H. F. (2009). Impurity diffusion activation energies in Al from first principles. Physical Review B (Condensed Matter and Materials Physics), 79(5), 054304–54312.
Abstract: Activation energies for vacancy-mediated impurity diffusion in face-centered-cubic aluminum have been computed ab initio for all technologically important alloying elements, as well as for most of the lanthanides. The so-called five-frequency rate model is used to establish the limiting vacancy interchange process. Many elements were shown to be limited by Al-vacancy interchanges. For these elements we showed that the diffusion activation energy is rather close to that for Al self-diffusion, and additionally the diffusion pre-exponential factor is of the same order as that for Al self-diffusion. The diffusion activation energy is shown to exhibit a linear relation with the solute partial molar volume in Al. In contrast, transition metals are shown to deviate strongly from these generalities. Diffusion of transition-metal atoms is limited by solute-vacancy interchanges that require remarkably high activation energies. Transition-metal diffusivities in Al show strong trends with the number of d-valence electrons but not with partial molar volume.
Keywords: ab initio calculations, aluminium, impurities, reaction kinetics theory, self-diffusion, vacancies (crystal)
|
|
Lefebvre, W., Danoix, F., Hallem, H., Forbord, B., Bostel, A., & Marthinsen, K. (2009). Precipitation kinetic of Al3(Sc,Zr) dispersoids in aluminium. Journal of Alloys and Compounds, 470(1-2), 107–110.
Abstract: The non-isothermal formation of Sc- and Zr-containing dispersoids in Al-Zr-Sc ternary alloys has been investigated by atom probe tomography (APT). In the early stages of precipitation, a high number density of Sc-rich clusters form. These clusters subsequently transform into Al3Sc particles with a L12 structure. When Zr diffusion becomes significant, Zr atoms are found to segregate to Al3Sc/α-Al matrix interfaces. Further annealing at 748 K gives rise to a duplex core/shell structure.
Keywords: Al-Zr-Sc, Core-shell, Diffusion, Dispersoid, Dispersoids, Heating, Ramp
|
|
|
Yoshi-yama, T., Hasebe, K., & Mannami, M. -hiko. (1968). Al3Li Superlattice in Al-4.5wt.% Li Alloy. Journal of the Physical Society of Japan, 25(3), 908.
|
|
Amouyal, Y., Mao, Z., & Seidman, D. N. (2009). Phase partitioning and site-preference of hafnium in the gamma[sup [prime]](L1[sub 2])/ gamma(fcc) system in Ni-based superalloys: An atom-probe tomographic and first-principles study. Applied Physics Letters, 95(16), 161909.
Abstract: Atom-probe tomography (APT) and first-principles calculations are employed to investigate the partitioning of Hf in the gamma[prime](L12)/gamma(fcc) phases in two multicomponent Ni-based superalloys. APT results indicate strong partitioning of Hf atoms to the gamma(fcc)-phase. We perform first-principles calculations of the substitutional formation energy of Hf for a model gamma(Ni)/gamma[prime](Ni3Al) system indicating Hf partitioning to the gamma[prime]-phase. Additional calculations of the Hf–Cr binding energy suggest, however, that Cr atoms, which partition to the gamma-phase, have a strong attractive binding energy with Hf atoms, thus predicting a reversal of the Hf partitioning in favor of the gamma-phase due to alloying with Cr.
Keywords: ab initio calculations; aluminium alloys; atom probe field ion microscopy; binding energy; hafnium alloys; nickel alloys; phase diagrams; superalloys; tomography
|
|
Razafindrazaka, M., Tanguy, D., & Delafosse, D. (2009). Defect hardening modeled in 2D discrete dislocation dynamics. Materials Science and Engineering: A, 527(1-2), 150–156.
Abstract: Two-dimensional discrete dislocation dynamics simulations are used to model the plastic deformation of an fcc metallic material containing large densities of defects. An obstacle model is proposed, based on the line tension concept. Increasing yield strength and hardening are obtained when the obstacle density is increased and destroyable junctions are included. A high dislocation source density is used to obtain a good dissemination of dislocations. Over 30% of the total density is stored as junctions. Slip is shown to be localized within a few intense slip bands, whatever the obstacle density. This localization is quantified as a function of the density of obstacles.
Keywords: Dislocation theory, Hardening
|
|
|
