Quantitative expression of stress-strain curve including strain rate dependence in a Ti-Fe-O alloy was studied at temperatures between 77 and 293 K.
In order to evaluate the strain-rate-independent component, in the first place, the authors endeavored to obtain the stress-strain curve as the curve at 0 strain rate through relaxation tests under constant crosshead displacement. The relaxation-saturated stress-strain points made a single curve. The authors named this single curve as "Base Curve". The Base Curve was good fitted to the Swift's equation in the following form: σ
Base(ε)=
A(ε+
b)
n, where σ
Base(ε) is the stress on the Base Curve, ε the plastic strain,
n the exponent, and
A and
b are coefficients.
The stress-strain curves at the strain rate between 2.8×10
-5 and 3.0×10
-2 s
-1 were parallel to the Base Curve. Namely, the strain-rate-dependent component, σ
*, was independent of strain at a constant strain rate. The relation between σ
* and strain rate, γ, was expressed in the following form: σ
*=
Bγ
m, where
B coefficient and
m exponent.
Finally, the equation, σ=
A(ε+
b)
n+
Bγ
m, is derived for the expression of flow stress-plastic strain relation under the deformation at a constant strain rate.
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