Materials Science and Engineering A 504 (2009) 24–35
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Materials Science and Engineering A
journal homepage: www.elsevier.com/locate/msea
Study of texture evolution in metastable -Ti alloy as a function of
strain path and its effect on transformation texture
Nilesh P. Gurao, Ashkar Ali A, Satyam Suwas
∗
Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India
article info
Article history:
Received 2 July 2008
Received in revised form
30 September 2008
Accepted 21 November 2008
Keywords:
Texture
Beta titanium alloys
Mode of rolling
Transformation texture
Recrystallization texture
abstract
Texture evolution in a low cost beta titanium alloy was studied for different modes of rolling and heat
treatments. The alloy was cold rolled by unidirectional and multi-step cross rolling. The cold rolled mate-
rial was either aged directly or recrystallized and then aged. The evolution of texture in and phases
were studied. The rolling texture of phase that is characterized by the gamma fiber is stronger for MSCR
than UDR; while the trend is reversed on recrystallization. The mode of rolling affects transformation
texture on aging with smaller lath size and stronger texture in UDR than in MSCR. The defect structure
in phase influences the evolution of texture on aging. A stronger defect structure in phase leads to
variant selection with the rolled samples showing fewer variants than the recrystallized samples.
© 2008 Elsevier B.V. All rights reserved.
1. Introduction
It is well known that alloying titanium with elements like Nb,
Mo, Ta, V, Hf etc leads to stabilizing the phase at room tempera-
ture, and hence the so-called metastable -Ti alloy. Upto a certain
amount of stabilizer content, the phase remains metastable,
which upon aging at a suitable temperature leads to the formation
of phase. These metastable -Ti alloys, characterized by high spe-
cific strength, sufficient ductility and fracture toughness along with
excellent corrosion resistance, find extensive use in structural and
biomedical applications. The most important feature of these alloys
which makes them suitable for various applications is that a bal-
ance of various properties can be achieved by subjecting them to
proper thermomechanical treatments. However, these alloys suf-
fer from a serious limitation of high cost [1], due to titanium itself
plus alloying elements like vanadium to stabilize the phase at
room temperature that renders them unsuitable for non-aerospace
applications. The full potential of these alloys has not yet being
exploited, particularly in the automobile industry, due to their high
cost and hence there has been a motivation for developing low
cost titanium alloys. One such alloy TIMETAL LCB
®
has been
developed by replacing the costly vanadium with cheap and eas-
ily available Fe–Mo and Fe–V masteralloys which are widely used
in steel industry. Processing of metastable -Ti alloys as needed to
∗
Corresponding author.
E-mail address: satyamsuwas@met.iisc.ernet.in (S. Suwas).
fabricate components, involves deformation plus thermal process-
ing. Both these processes lead to modification in crystallographic
texture.
It is well known that the phase of metastable -Ti alloys trans-
form to ( + ) structure. During phase transformation from to
phase, Burger’s orientation relationship [2] is generally followed,
i.e. {0001}
˛
101
ˇ
and {11
¯
20}
˛
111
ˇ
, however due to
symmetry of the crystal, a single orientation gives rise to 12
equivalent orientations with equal probability [3]. Under cer-
tain thermal and thermomechanical treatments, it is possible to
get higher probability for certain orientation, rather than all ori-
entations being equally probable. This phenomenon is known as
Variant selection. This effect which comes into play at the crys-
tallographic scale, also affects the morphology of the transformed
phase. Since texture plays an important role in determining
mechanical properties of HCP structured () Ti and Ti alloys due
to the inherent anisotropy of HCP crystal lattice, the knowledge of
to transformation is essential for processing property optimiza-
tion.
A number of comprehensive studies have been carried out on
the evolution of texture during hot deformation or heat treatment
in phase of ( + ) [4–13] or (
2
+ ) [14–18] titanium alloys and
the evolution of corresponding transformation texture. However,
in ( + ) Ti alloy, the high temperature phase cannot be retained
at room temperature; therefore, the experimental techniques are
not free from limitations. In the (
2
+ ) alloys although, the high
temperature phase can be retained, there is a limited scope
in changing the texture of high temperature phase. Therefore,
0921-5093/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.msea.2008.11.053