D. Banerjee et al., SUBSTRUCTURE IN TITANIUM-ALLOY MARTENSITE, Philosophical magazine. A. Physics of condensed matter. Structure, defects and mechanical properties, 77(2), 1998, pp. 299-323
Hexagonal plate martensite in titanium alloys contains a dense substru
cture whose character and origins have not been completely addressed i
n the literature. The substructure is shown to consist of columnar dom
ains which extend along basal planes from the midrib of the martensite
plates to the habit plane and are bound in the third dimension by sho
rt segments of non-crystallographic surfaces roughly perpendicular to
the habit plane. The domain structure gives rise to various diffractio
n effects consisting of relrods of intensity along the c axis and relp
lanes of intensity roughly perpendicular to the non-crystallo graphic
interfaces. A mechanism for domain formation is proposed on the basis
of the Burgers mechanism for the bcc-to-hcp martensite transformation.
An atom shuffle which is an intrinsic part of this mechanism can occu
r in either of two alternative directions and will result in domains r
elated by the displacement vector 1/6[20<(23)over bar>]. The similiari
ty between this substructure and the domain structure in martensites o
f noble-metal alloys is pointed out, and orthorhombic martensite in a
titanium alloy is shown to contain a similar domain structure which ca
n form from an identical mechanism.