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The effect of quench rate on the martensitic transformation in Fe−C alloys |
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| Authors: | G S Ansell S J Donachie R W Messler |
| Affiliation: | 1. Materials Division, Rensselaer Polytechnic Institute, Troy, N. Y. 2. Mercia Research Laboratory, International Nickel Co., Sterling Forest, Suffern, N. Y. 3. Grumman Aerospace Corp., Bethpage, L. I., N. Y. |
| Abstract: | The effect of very high quench rates on the transformation kinetics of a series of Fe?C and low-alloy steels and the morphology of an Fe?14Ni-0.76C alloy was investigated. TheM S temperatures of the Fe?C and Fe?C?X alloys increased between 90° and 122°C in a sigmoidal fashion over a quench rate range from 2,750° to 24,800°C per sec. The sensitivity of theM s temperature to the quench rate from the austenitizing temperature to 315°C was shown to be related to the influence of the third alloying element on the diffusivity of carbon in austenite. Transmission electron microscopy and optical metallography showed that the morphology of an Fe?14Ni?0.76C martensite is changed from a lath structure in slow quenched samples to a plate structure in fast quenched samples. The substructure of the untransformed austenite adjacent to the martensite plates changed from planar dislocation arrays to dislocation tangles with increased quench rate. These results were explained using a model for ferrous martensite strengthening based upon the extent of carbon segregation to imperfections in the austenite during cooling. |
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