IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
Fig.2 Crystal orientation map of
phase for heat treated wire
sample. Inverse pole figure
contour shows primary
concentration near to (1 1 -2 2)
was deformed by two modes
(namely wire drawing and cold
rolling), followed by β solution
annealing at 1273 K/1 hour
and slow cooling to
room temperature, resulting
in α+β→β→α+β phase
transformations. The evolution
of crystallographic texture in
the transformed product has
been characterized using X-ray
Diffraction (XRD) and SEM-
EBSD (Scanning Electron
Microscopy-Electron Back
Scattered Diffraction)
techniques. Fig. 1 shows the
XRD intensity of the various (h k
i l) α crystallographic planes, for
the wire/sheet samples before
and after heat treatment,
compared with the powder
sample. An increased relative
intensity of certain plane
suggests preferential
crystallographic alignment or
'texture'. Before heat treatment,
a 'deformation texture' of [1 0 -
1 0] α //AD (Axial direction) for
the wire sample, and a (0 0 0
2) α /ND (Normal direction)
texture for the sheet sample was
observed. Heat treatment
resulted in a different and more
pronounced 'transformation
texture' of [1 1 -2 2] α //AD for
the wire, and (1 1 -2 0) α //ND
for the sheet sample. SEM-
EBSD analysis was used to
study microscopic detail of
texture. Fig. 2 and 3 show the
'Crystal Orientation Map' for
the heat treated wire, sheet
samples respectively, depicting
the type of crystallographic
planes (color indexed) which
are aligned with the sample
surface. The EBSD result is in
concordance with XRD. The
comparison of crystallographic
orientation of α lamellae and its
neighboring β lamellae showed
'Burgers Orientation Relation'
(BOR) to be obeyed. Thus, the
alloy is seen to acquire a
'deformation texture' dictated by
Fig.3 Crystal orientation map
of α and β lamellas for heat
treated sheet sample.-grains
are oriented with (1 1 -2 0)
alignment.
the deformation mode. Heat
treatment leads to high
temperature β-texture and a
distinct 'transformation texture'
of α, as dictated by the
orientation relationship during
β to α transformation.
106 FUEL CYCLE