The influence of deformation-induced martensite on fatigue crack growth in metastable austenitic steels
- Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering
This paper discusses the influence of mechanically induced martensitic transformations on the fatigue crack growth rate in metastable austenitic steels. The behavior of 304L and 304LN stainless steels is used to clarify the transformation effect. Inducing a mechanical transformation to martensite reduces the fatigue crack growth rate and increases the threshold intensity for crack growth. However, the benefit decreases as the load ratio (R) increases, even though a higher R causes more extensive transformation. The experimental data can be explained on the assumption that the fatigue crack growth rate is governed by {Delta}K{sub eff} = K{sub max}-max{l_brace}K{sub min},K{sub t},K{sub c}{r_brace}, where K{sub t} is the transformation-induced relaxation of the cyclic stress intensity, and K{sub c} is the stress intensity for macroscopic crack closure. The relaxation, K{sub t}, is most important at low values of R, and at higher values of {Delta}K, the conditions under which the crack tip transformation has its most dramatic effect on the fatigue crack growth rate. The crack growth rate is also retarded by the dual-phase microstructure produced by the transformation at the crack tip. The microstructural effect appears to dominate at high load ratios, where K{sub min} > K{sub t}.
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 293066
- Report Number(s):
- CONF-970980--; ISBN 0-87339-382-1
- Country of Publication:
- United States
- Language:
- English
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