【摘 要】
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The effect of austenite deformation and continuous cooling on the evolution of microstructure in a high temperature processing(HTP)concept pipeline steel was investigated in this research.It was found
【机 构】
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Department of Materials Science and Engineering,The University of Sheffield,Sir Robert Hadfield Buil
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The effect of austenite deformation and continuous cooling on the evolution of microstructure in a high temperature processing(HTP)concept pipeline steel was investigated in this research.It was found that without austenite deformation,the transformed microstructure consists of blocky quasi-polygonal ferrite(QF)grains and parallel bainitic ferrite(BF)laths at a cooling rate of 0.5 °C/s.With increased cooling rates,the fraction of BF laths is raised and the microstructure reaches full BF at cooling rates of 5°C/s and higher.After austenite deformation,BF laths disappear at low cooling rates of 0.5~1°C/s and QF is the dominant phase.At a higher cooling rate of 5°C/s,the fraction of QF is reduced and acicualr ferrite(AF)becomes the main phase surrounded by QF grains.Increasing the cooling rate further,QF disappears and fthe raction of BF rises,finally leading to a BF dominant microstructure at a cooling rate of 50°C/s.Factors influencing these microstructure evolution characteristics were discussed,including segregation of niobium atoms at austenite grain boundary and the introduction of intragranular nucleation sites by deformation.
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