Mechanical Behaviour

Metallurgical Transactions A

, 6:1693

First online:

Measurement of the mechanical state of a low alloy steel at elevated temperature

  • D. A. WoodfordAffiliated withCorporate Research and Development Center, General Electric Company

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Load relaxation tests on a Cr-Mo-V steel are used to generate stress-strain rate curves at high temperature. It is shown that the mechanical state as described by these curves is sensitive to the deformation history, such that the alloy undergoes a hardening and subsequent softening as strain is accumulated. However, these changes are quite small in successive tests and it is shown that results at different temperatures can be made to coincide by a suitable translation of the strain rate scale at nearly constant mechanical state. The result is a stress-strain rate curve over about twelve orders of magnitude in strain rate so that initial creep rates at stresses far beyond the range covered at each temperature can be estimated.

A previously proposed analytical expression for similar data on high purity aluminum fits the present data surprisingly well. From this expression a mechanical state, or hardness parameter, σ*, is obtained. For any value of stress, the value of σ* and its associated parameter, ε*, uniquely define the strain rate.