The structure, thickness and chemistry of antiphase domain boundaries in heat-treated, rapidly solidified Ni3Al

Citation
Jf. Perez et al., The structure, thickness and chemistry of antiphase domain boundaries in heat-treated, rapidly solidified Ni3Al, PHIL MAG A, 79(1), 1999, pp. 179-192
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS ANDMECHANICAL PROPERTIES
ISSN journal
1364-2804 → ACNP
Volume
79
Issue
1
Year of publication
1999
Pages
179 - 192
Database
ISI
SICI code
1364-2804(199901)79:1<179:TSTACO>2.0.ZU;2-7
Abstract
Antiphase boundaries (APBs) in a rapidly solidified Ni3Al alloy have been e xamined by transmission electron microscopy in the as-solidified state and after annealing. Dark field imaging suggests that the APE thickness increas es with temperature during annealing and that a dark, disordered phase appe ars at temperatures above about 800 degrees C. The boundary region at high temperatures has a chemical composition close to that expected from the pha se diagram for the disordered phase, namely containing about 15 at.% Al. Ex amination of APBs by high-resolution electron microscopy does not confirm t he disorder. however, and the so-called disordered regions showing dark con trast may in fact be caused by the significantly modified chemistry of thes e ordered regions. It is not clear whether disorder may form at high temper ature when the average alloy composition enters the two-phase ordered + dis ordered region, or whether simply extensive segregation takes place to the APB without the true appearance of a second, disordered phase. Similar effe cts occurring at grain boundaries would lead to a structure dependent on bo th composition and temperature, with the mechanical behaviour of the materi al depending on the structural state.