Investigate the effect of molybdenum on precipitation in coiled strip cast niobium steels using correlative microscopy
Loading...
Files
Date
2016-02-04
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Microscopy and Microanalysis Society
Abstract
Steels containing both Nb and Mo have been reported to exhibit superior strength as compared to those containing only Nb. This has been explained by the formation of harder microstructures, such as bainite and acicular ferrite, and denser and finer precipitates promoted by the addition of Mo. For further improvement of this strengthening method, a fundamental understanding of the effect of Mo on precipitation in steels is necessary. Transmission electron microscopy (TEM) is commonly used for precipitation studies and provides direct imaging of the precipitates, however it only allows local observation and it is thus non statistical by nature and makes it difficult to estimate precipitates volume fraction. On the other hand, small angle neutron scattering (SANS) can be used as a statistical technique to quantitatively study precipitation. Consequently, TEM and SANS provide complementary information and are thus powerful when used in combination. SANS measurement was used to determine the size distribution and volume fraction of particles. Meanwhile, TEM observation was performed to obtain the distribution, morphology, chemistry and size of particles on the samples investigated by SANS. In this research, the effect of Mo on precipitate formation is studied in steels processed with the recently developed direct strip casting process and subsequent coiling treatment. Direct strip casting is a revolutionary casting technique that integrates casting and subsequent rolling together with rapid solidification and cooling rates, which not only simplifies the process, but also confers superior energy-saving as compared to conventional alloy thermomechanical processing. The strip cast samples were isothermally coiled at 700 ̊C for durations up to 10000 seconds. TEM results show that interphase precipitates were formed in both alloys and the size of particles were in the range of 10 nm. Additionally, SANS was used to quantify the precipitate size and volume fraction evolution during coiling.
Description
Keywords
Molybdenum, Refractory metals, Niobium, Steels, Ferrite, Transmission electron microscopy, Small angle scattering
Citation
Jiang, L., Dorin, T., Marceau, R., Wood, K., Hodgson, P., & Standford, N. (2016). Investigate the effect of molybdenum on precipitation in coiled strip cast niobium steels using correlative microscopy. Paper presented to ACMM24 : Australian Conference on Microscopy and Analysis : Melbourne Convention and Exhibition Centre, 31 Jan-4 Feb 2016, (pp. 81).