(011)γ/(101)γ order twin of γ lamella in a Ti-40 at.% Al alloy
Journal
Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
Journal Volume
65
Journal Issue
1
Pages
15-28
Date Issued
1992
Author(s)
Yang Y.S.
Abstract
Transmission electron microscopic study on a α2 + γ two-phases Ti-40 at.% Al alloy demonstrates that (011)γ/(101)γ twin does occur in TiAl. Differently-orientated γ regions are observed to coexist within the same γ lamella with the (011)γ/(101)γ twin plane as their boundary. The variants pair corresponding to these differently-orientated γ regions should come from variants which have the same stacking sequence. The mechanism for the formation of (011)γ/(101)γ twin plane is suggested to grow from the ‘APB-induced fault’ formed in the γ lamella during the precipitation transformation of α2→α2 + γ. Total strain induced by the structure change (h.c.p.→F.C.C.) and by the tetragonality of γ phase during the precipitation transformation can be minimized by a composite of (111)γ and (011)γ twins coexisting in γ lamellae. © 1992 Taylor & Francis Group, LLC.
Type
journal article