Bainite Transformation of Low-carbon and Boron-containing Steel under Continuous Cooling

The effects of deformation temperature and strain on bainite transformation of low carbon steel and boroncontaining steel were investigated under continuous cooling conditions by means of dilatometric measurement and microstructure observation.The results show that with decreasing the deformation temperature from 1 000to 800 ℃and increasing strains,bainite start temperature for boron-containing low carbon steel increases,whereas it decreases for low carbon steel under the same condition.The bainite microstructures are easily obtained for boron-containing steel deformed at different temperatures and different strains compared with plain low carbon steel.With increasing the continuous cooling rate,the bainite start temperature under deformed condition is about 20 ℃ higher than that under undeformed condition for boron-containing steel,but it changes slightly when the cooling rate is 20℃/s or more.     

Experimental Study and Kinetic Calculation on Migration of γ/α Interface Boundary During High Temperature Aging for 2205 Duplex Stainless Steel

Aging treatments in the temperature range of 1000 to 1200 ℃ for different time intervals(10,30,and 60 min)in a solution-treated 2205 duplex stainless steel(DSS)are carried out respectively.The migration of γ/α interface boundary after different aging treatments is measured by optical metallograph and calculated by DICTRA software.The experimental results are in agreement with calculated ones.The migration of γ/α interface boundary with increased keeping time depends on the chemical potential of chromium in each phase.At aging temperature of 1100 ℃,the back diffusion effect of chromium results in the opposite direction migration of γ/α interface.Therefore,the ferrite volume fraction is lower at first and then it is higher after 1800 s diffusion.