Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 675, Issue -, Pages 243-252Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2016.08.058
Keywords
Copper precipitation; Atom probe tomography; Precipitation hardening; Coarsening; Austenitic stainless steel
Categories
Funding
- National Natural Science Foundation of China [51371168, 51501188]
- National Natural Science Foundation of China Research Fund for International Young Scientists [51450110439]
- National Key Research and Development Program [2016YFB0300205]
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The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 degrees C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38 +/- 0.46 nm to 2.39 +/- 0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels. (C) 2016 Elsevier B.V. All rights reserved.
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