Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
A Study on Temperature and Strain Rate Dependences of Yield Stress, and Ductile-Brittle Transition in Mild Steel
Kazuyoshi NISHINOHiroo HONMA
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1970 Volume 56 Issue 7 Pages 859-868

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Abstract

The dependence of the yield stress of mild steel at low temperatures on grain size, strain rate and temperature was studied mainly by compressive deformation test.
(1) The following equation relating strain rate (ε), temprature (T) and frictional stress (σt) of Petch equation was obtained;
This is applicable when at is in the range of 8.7 to 28.2 kg/mm2. Strain rate exponent n and activation energy E are constant, both being independent on temperature, strain rate or stress. Above this stress level, n becomes larger but E is substantially invariable.
(2) According to the study on BCC metals, it can be said that they behave in a similar manner to mild steel. That is, is is in the range of 7 to 9, being constant and specific to BCC metals, and in addition, E is approximately proportional to an energy of μb3, where μ is the shear modulus and b the Burgers vector.
(3) The relations between strain rate, grain size and ductile-brittle transition temperature were studied by using the above equation, and the calculated temperatures are generally in accordance with the measured values.

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© The Iron and Steel Institute of Japan
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