日本金属学会誌

J. Japan Inst. Metals, Vol. 49, No. 3 (1985),
pp. 195-202

Deformation Behavior of Polycrystalline Alpha-Titanium at High Temperature

Meng~Xin Cui1 and Hiroshi Oikawa2

1Research Associate, Graduate School, Tohoku University, on leave from The Northeastern Institute of Heavy Machines, Tsitsihar
2Department of Materials Science, Faculty of Engineering, Tohoku University, Sendai

Abstract:

Tensile tests of commercially pure titanium, the grain size of which was about 0.1 mm, were conducted in argon at 843--1100 K under 3.3×10-6--3.3×10-2 s-1. The true strain-rate, \dotε, was related with the power law of the maximum (steady-state) stress, σ s, which was corrected for straining under the constant true strain-rate; the stress exponent n was 4.36±0.13. The activation energy for steady-state deformation, Qc, was estimated as 184.4±1.2 kJ/mol, taking the temperature dependence of shear modulus into account. This value of Qc is close to that for the tracer diffusion. Dorn equation is applied to a polycrystalline alpha-titanium using diffusion coefficients given by Dyment (1980) and shear moduli given by Fisher and Renken (1964): A=3.2≥nfrac()0pt{}{+1.0}{-0.8}×105 and n=4.20±0.07. The effect of grain size, d, was investigated in the range from 0.1 mm to 1.3 mm. The value of n does not depend on d. The factor A depends on d in fine-grained samples, but in coarse-grained samples, it becomes independent of d: A=7.0≥nfrac()0pt{}{+1.4}{-1.2}×104. Coarse-grained alpha titanium is significantly weak in respect of the normalized strength as compared with ordinary hcp metals.


(Received 1984/12/7)

Keywords:

hexagonal metal, polycrystalline alpha-titanium, tensile test, high temperature, steady-state creep, stress exponent, activation energy


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