ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Formation of austenite strongly influences the microstructures and mechanical propertiesof dual phase steels. In present work, austenization process during intercritical annealing was studiedin a Fe-C-Mn steel using Gleeble-1500 thermal simulator and quantitative microscopy. Theexperimental results show that austenite formation is separated into three different stages: (i) growthof high carbon austenite into pearlite rapidly until pearlite dissolution is completed; (ii) slowergrowth of austenite into ferrite; (iii) very slow equilibration between ferrite and austenite. Thethermodynamic and kinetic analyses show that growth of austenite into ferrite is controlled by carbondiffusion in austenite in the primary stage and manganese diffusion in ferrite in the subsequent stagebecause diffusion coefficient of Mn in ferrite is several orders of magnitude smaller than that of C inaustenite. The slow final equilibration between ferrite and austenite is obtained by manganesediffusion through the austenite. Based on the analysis, one dimensional diffusion model ofintercritical austenization was developed and solved using finite volume method on the assumptionthat solute flux was local balance at interface, and the kinetics calculated was compared withexperimental results. Simulated results indicate that growth of austenite reaches paraequilibrium inabout one second, but remains thousands of seconds to reach final equilibrium. Simulatedconcentration profiles show that manganese atoms transferred from ferrite congregate in austenitenear phase interface, which is consistent with the experimental phenomenon
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/18/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.575-578.1062.pdf
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