Title: Microstructure Transformation of Ultra-high Carbon Steel during Austempering at Temperature of 250℃~350℃
Abstract: Ultra-high carbon steel of the following composition was chosen for investigation,1.40wt% C,1.50 wt%Cr,1.50 wt%Al,balance Fe and a little impurities.Austempered bainitic morphology and formation mechanism under the isothermal temperature of 250℃~350℃ were discussed.The results showed that the incubation period shortens and transformation incompleteness increases with increasing isothermal temperature.At the same time,the bainite plate becomes thicker and grows more laterally.The residual austenite decomposes to become cementite and ferrite during the isothermal process after bainite transformation complete.For the samples with a slight baintite transformation,bainite continues to form during immediate aircooling.It was revealed that bainite transformation was controlled by two factors:stress and atomic diffusion. The stress predominates by shear mechanism under low isothermal temperature.The diffusion predominates by diffusion mechanism under high isothermal temperature,resulting in the thickness increase of the bainite plate.
Publication Year: 2014
Publication Date: 2014-01-01
Language: en
Type: article
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