IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
dissolver cell is given in Fig.1.
The piping engineering of all
the cells have been completed
except the dissolver cell. 3D
drawings of these have helped
in visualizing effectively the
erection and maintenance
problems. Most of the
packages for piping have been
tendered out. The erection of
equipment and piping will be
completed and the plant will be
ready for commissioning by
2009.
The construction of the head
end facility, in which FBTR and
PFBR spent fuel will be
dismantled, is in progress. The
detailed design of this facility
has been completed by the
consultants. This facility will be
integrated with the rest of the
plant by 2010.
IV.C. Materials for Fuel Cycle
IV.C.1. Athermal Decomposition Modes of Phase in a Ti-5%Ta-1.8%Nb Alloy
Titanium alloys are chosen for
a variety of industrial
applications due to their high
strength/weight ratio and
excellent corrosion resistance,
which can be achieved by
tailoring the microstructure.
The origin of a myriad of
microstructures is due to a
variety of phase
transformations of the high
temperature BCC β phase,
which is unstable at room
temperature. However, the
stability of β phase at room
temperature can be influenced
by addition of β stabilizing
elements and cooling rate.
Lean β as well as solute rich
alloys undergo a diffusionless
martensitic transformation. In
the former alloys, β quenching
results in a hexagonal
martensite while in the latter an
orthorhombic martensite forms.
Another class of transformation
namely the displacive omega
transformation is also reported
to occur in group IV metals Ti,
Zr, Hf etc. The presence of
both martensite and omega
phase in a Ti-5Ta-1.8Nb alloy
subjected to isothermal
treatments in different phase
fields has been investigated.
Transmission Electron
Microscopy studies established
that the α+β Ti-5Ta-1.8Nb
(a)
(b)
β
α
0.5 µm
0.05 µm
Fig.1 (a) Transformed β microstructure on isothermal treatment in α + β phase field below Ms temperature; inset
is the diffraction pattern showing the presence of α,β and ω phases (b) Darkfield micrograph showing
fine ellipsoidal particles of ω phase in retained β
104 FUEL CYCLE