Influence of Austenite Grain Size on Martensite Start Temperature of Nb-V-Ti Microalloyed Ultra-High Strength Steel

Abstract:

In order to investigate the effect of austenite grain size on martensite start temperature of Nb-V-Ti micro-alloyed ultra-high strength steel, the phase transformation features of Nb-V-Ti micro-alloyed steel was investigated. It has been found that martensite start temperature increased with the increase of austenite grain size as a consequence of the increase of austenitizing temperature. Based on microstructure observation, two types of MX carbonitrides with different compositions and morphologies have been identified. With the increase of the austenite grain size, both the volume fraction of precipitates and the dislocation density decreased, which may be induced by the strengthening of the austenite matrix directly and increasing the resistance of austenite to plastic deformation. Hence, the increase of martensite start temperature could be attributed to a decrease in volume fraction of precipitates and dislocation density.

• Periodical: Materials Science Forum (Volume 848)
• Pages: 624-632
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.848.624
• Online since: March 2016
• Authors: Ji Dong, Chen Xi Liu, Yong Chang Liu, Chong Li, Qian Ying Guo, Hui Jun Li
• Keywords: Austenite Grain Size, Dislocation Density, Martensite Start Temperature, Nb-V-Ti Microalloyed Ultra-High Strength Steel, Precipitate

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