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Martensitic transformation of reversed austenite in a low-carbon 7Ni steel
Wei Hou, QinDong Liu*, JianFeng Gu*
aScience and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China,Chengdu, People’s Republic of China;
bInstitute of Materials Modification and Modelling, School ofMaterials Science and Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of China;
cChongqing Research Institute of Shanghai Jiao Tong University, Chongqing, People’s Republic of China
Abstract:
Reverse transformation plays an important role in phasecontrolling of 7Ni steel. However, little attention has beenpaid on the martensitic transformation behaviour of thismaterial. In this research, martensitic transformationkinetics and the martensite-start temperature (Ms) ofreversed austenite is studied in a 7Ni steel by dilatometryand microstructure analysis. It is shown that thetransformation kinetics can be described by an exponentialKoistinen-Marburger (KM) equation rather than by thetraditional KM equation. An abnormal phenomenon wasfound, namely that although reversed austenite is enrichedwith solute elements and has a smaller grain size, nodistinct decrease of Ms occurred. This may be caused by adecreased critical driving force for martensitic nucleation,including those associated with strain and interfacialenergies, as it was found that the orientation of freshmartensite is close to that of the surrounding temperedmartensite.
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