The early stage of gamma prime precipitation in a nickel-silicon alloy

Journal Article · Sat Dec 01 04:00:00 EST 1984 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(84)90372-7· OSTI ID:5038694

Dvorack, M A; Chen, H; Polat, S

The gamma prime (..gamma../sup 1/) precipitation from supersaturated Ni-base superalloys has long been an interesting subject owing to their desirable mechanical properties for high temperature applications on one hand, and to their well behaved kinetic development in accordance with the diffusion-controlled coarsening theory on the other. Previous experimental observations in regard to the precipitation kinetics in these alloys have been primarily concentrated on the coarsening behavior at long aging times and relatively high temperatures; very little work has been done concerning the early stage of particle growth. This is so because the particle growth period is often too rapid to be detectable at high temperatures. Precipitation from a supersaturated solid solution usually occurs initially by nucleation, followed by growth, and completed by coarsening. Nucleation is a process by which embryos of the second phase are formed due to the reduction of the volume free energy in competition with the surface energy generated by the interface between the embryo and the matrix. Those embryos with radii larger than certain critical size will then grow while others dissolve. During the coarsening stage, larger particles grow at the expense of the smaller ones due to the higher solubility of the small particles which have a larger ratio of surface to volume. Although the theoretical treatment of such a precipitation process has been carried out in various degrees of sophistication, it is generally agreed that the most rigorous approach was the one developed by Lifshitz and Slyozov, and independently by Wagner: the commonly known LSW theory of Ostwald ripening.

• Research Organization: Department of Metallurgy and Mining Engineering and the Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois
• OSTI ID: 5038694
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 18:12; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
CHEMICAL REACTION KINETICS
CRYSTAL GROWTH
DIFFUSION
ELECTROMAGNETIC RADIATION
GAMMA RADIATION
GRAIN GROWTH
IONIZING RADIATIONS
KINETICS
MECHANICAL PROPERTIES
NICKEL ALLOYS
NICKEL BASE ALLOYS
NUCLEATION
PARTICLE SIZE
PRECIPITATION
RADIATIONS
REACTION KINETICS
SATURATION
SEPARATION PROCESSES
SILICON ALLOYS
SIZE
SOLUBILITY
SUPERSATURATION