High Temperature X-Ray Decomposition Studies of Alpha Phase Nickel-Silicon and Beta Phase Copper-Aluminum-Nickel Alloys

In-situ high temperature X-ray diffraction studies have been performed in order to study the transformation mechanisms and associated kinetics regarding the decomposition and precipitation processes of two metallic alloys of commercial significance: Ni-12.5 at% Si and Cu-28.15 at% Al-3.88 at% Ni. Earlier resistivity measurements of the Ni-Si superalloy of the same composition yielded what was thought to be an apparent order-disorder instability temperature, below which formation of an ordered (gamma)' Ni(,3)Si phase occurred by a continuous transformation, and above which precipitation occurred by nucleation and growth processes. The X-ray results, however, have shown that the precipitation is actually dependent upon the thermal history of the specimen. In addition, cyclic heating and cooling of the specimen at elevated temperatures alters the growth rate of the ordered phase, thereby giving reason to believe that, for the particular composition studied, the growth of the ordered phase is simply based upon classical nucleation and growth phenomena.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Metallurgical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Dvorack, Michael Albert

• Engineering, Metallurgy

Identifier

(UMI)AAI8409766

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71803