High temperature deformation of pure titanium, (α+β) and β titanium alloys were studied by means of compression tests over the range of strain rate from 10
-1s
-1to 10
-3 s
-1 and at temperatures between 973 K and 1473 K, and the results obtained were analysed by using Zener-Hollomon parameter (
Z).
The following results were obtained ;
(1) Maximum flow stress, σ
max, was correlated with working temperature,
T, and strain rate, ε, approximately by the following deformation equation;
Z(=ε exp(
Q/
RT))=
A(sin
h(ασ
max))
nwhere
Q: hot-working activation energy, n: stress exponent,
R: gas constant,
A and a: constants.
(2)The value of
Q in α+β phase was much larger than that in β phase. So the deformation mechanism in α+β phase must be different from that in β phase. The value of
Q in β Ti was almost the same as the activation energy for the self-diffusion of Ti.
(3) Deformation structure became to equiaxed microstructure by continuous recrystallization in the range of
Z less than the critical value,
Zc. The recrystallized grain size was determined only by the deformation condition
Z, and did not depend on the initial grain size.
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