An atom probe investigation of the influence of trace impurities on the mechanical behavior of NiAl
Atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM) have been used to investigate the influence of trace metallic impurities on the enormous increase in the yield stress of boron-doped NiAl. Previous atom probe studies of NiAl containing 0.12 at. % boron had demonstrated that 0.026 at. % of the boron was in solid solution. The remainder reacted with trace metallic impurities, presumably present in high purity Ni, to form ultrafine MB{sub 2} precipitates ranging in size from less than 2 nm to 20 nm. Atom probe measurements had shown that their number densities were significant enough to make the dominant contribution to the observed increase in yield stress. An attempt was made in the present work to minimize the effect of these precipitates by an additional aging treatment. Field ion microscope (FIM) and TEM micrographs revealed that 2 nm precipitates coarsened significantly during aging. Microstructure of aged NiAl was consistent with observed mechanical behavior showing a significantly smaller increase in the yield stress. An approximate value of the Orowan stress, based on TEM estimates of the size and number density of the precipitates, is in reasonable agreement with the measured value. This APFIM/TEM investigation has indicated a practical approach to minimize the detrimental role of trace impurities in NiAl.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Oak Ridge Inst. for Science and Education, TN (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10106389
- Report Number(s):
- CONF-931009-11; ON: DE94002797
- Resource Relation:
- Conference: Fall meeting of the Minerals, Metals and Materials Society: physical metallurgy and materials,Pittsburgh, PA (United States),17-21 Oct 1993; Other Information: PBD: [1993]
- Country of Publication:
- United States
- Language:
- English
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