The austenitizing temperature controls the carbon content of the austenite which,in turn,influences the structure and properties of cast irons after subsequent cooling to room temperature.In this paper,for a cast iron...The austenitizing temperature controls the carbon content of the austenite which,in turn,influences the structure and properties of cast irons after subsequent cooling to room temperature.In this paper,for a cast iron with known silicon content,a formula of calculating austenite carbon content at a certain austenitizing temperature was developed.This relationship can be used to more accurately select carbon content of austenite or austenitizing temperature to produce desired properties after subsequent cooling to room temperature.展开更多
Intercritical annealing（IA） at various temperatures followed by quenching and partitioning（IAQP） treatments was conducted on a cold-rolled Fe-0.2C-1.42Si-l.87Mn（wt%） sheet steel.Optimized microstructure and enha...Intercritical annealing（IA） at various temperatures followed by quenching and partitioning（IAQP） treatments was conducted on a cold-rolled Fe-0.2C-1.42Si-l.87Mn（wt%） sheet steel.Optimized microstructure and enhanced mechanical properties were achieved through appropriate adjustment of IA temperatures.The steel which was annealed at1,033 K for 600 s,then quenched to 573 K and partitioned at 693 K for 20 min,designated as 1033 QP steel,exhibits maximum 16.3 vol% retained austenite（RA） with good mechanical properties（ultimate tensile strength 886 MPa and total elongation 27%）.It was found that the thermal and mechanical stabilities of RA are mainly influenced by the combined effect of its average carbon content and amount of adjacent martensite.Furthermore,the transformation-induced plasticity effect increased the peak n-values observed at the second stage of the work hardening of IAQP steels.展开更多
The RAFM（reduced activation ferritic/martensitic）steels containing different tantalum contents（0wt.%,0.027wt.%,0.073wt.%）were designed and cast.Differential scanning calorimetry and optical microscopy were employe...The RAFM（reduced activation ferritic/martensitic）steels containing different tantalum contents（0wt.%,0.027wt.%,0.073wt.%）were designed and cast.Differential scanning calorimetry and optical microscopy were employed to explore the influence of tantalum content on the austenitic transformation of RAFM steels.The austenitic transformation kinetics was described by aphase-transformation model.The model,involving site saturation nucleation,diffusion-controlled growth and impingement correction,was established based on the classical Johnson-Mehl-Avrami-Kolmogorov model.The phase-transformation kinetics parameters,including D_0（pre-exponential factor for diffusion）and Q_d（activation energy for diffusion）,were calculated by fitting the experimental data and the kinetic model.The results indicated that the average grain size is decreased with the increase of tantalum.The values of A_（c1） and A_（c3） （onset and finish temperature of austenitic transformation,respectively）are increased by increasing the tantalum content.The increase of tantalum caused the decrease of D_0.However,Q_d is increased with the increase of tantalum.In addition,as a carbides forming element,tantalum would reduce the carbon diffusion coefficient and slow down the austenitic transformation rate.展开更多
基金supported by the scientific and technological project of China Textile Industry Association
文摘The austenitizing temperature controls the carbon content of the austenite which,in turn,influences the structure and properties of cast irons after subsequent cooling to room temperature.In this paper,for a cast iron with known silicon content,a formula of calculating austenite carbon content at a certain austenitizing temperature was developed.This relationship can be used to more accurately select carbon content of austenite or austenitizing temperature to produce desired properties after subsequent cooling to room temperature.
基金financially supported by the National Natural Science Foundation of China (No. 51174251)the National Basic Research Program of China (No. 2010CB630803)
文摘Intercritical annealing（IA） at various temperatures followed by quenching and partitioning（IAQP） treatments was conducted on a cold-rolled Fe-0.2C-1.42Si-l.87Mn（wt%） sheet steel.Optimized microstructure and enhanced mechanical properties were achieved through appropriate adjustment of IA temperatures.The steel which was annealed at1,033 K for 600 s,then quenched to 573 K and partitioned at 693 K for 20 min,designated as 1033 QP steel,exhibits maximum 16.3 vol% retained austenite（RA） with good mechanical properties（ultimate tensile strength 886 MPa and total elongation 27%）.It was found that the thermal and mechanical stabilities of RA are mainly influenced by the combined effect of its average carbon content and amount of adjacent martensite.Furthermore,the transformation-induced plasticity effect increased the peak n-values observed at the second stage of the work hardening of IAQP steels.
基金financially sponsored by the China National Funds for Distinguished Young Scientists (Granted No.51325401)the National Natural Science Foundation of China(Granted No.51501126)the National Magnetic Confinement Fusion Energy Research Program(Granted No.2015GB119001)
文摘The RAFM（reduced activation ferritic/martensitic）steels containing different tantalum contents（0wt.%,0.027wt.%,0.073wt.%）were designed and cast.Differential scanning calorimetry and optical microscopy were employed to explore the influence of tantalum content on the austenitic transformation of RAFM steels.The austenitic transformation kinetics was described by aphase-transformation model.The model,involving site saturation nucleation,diffusion-controlled growth and impingement correction,was established based on the classical Johnson-Mehl-Avrami-Kolmogorov model.The phase-transformation kinetics parameters,including D_0（pre-exponential factor for diffusion）and Q_d（activation energy for diffusion）,were calculated by fitting the experimental data and the kinetic model.The results indicated that the average grain size is decreased with the increase of tantalum.The values of A_（c1） and A_（c3） （onset and finish temperature of austenitic transformation,respectively）are increased by increasing the tantalum content.The increase of tantalum caused the decrease of D_0.However,Q_d is increased with the increase of tantalum.In addition,as a carbides forming element,tantalum would reduce the carbon diffusion coefficient and slow down the austenitic transformation rate.
