Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrate...Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrated that the initial mi- crostructures resulted from austenization at different temperatures strongly affect the microstructure evolution during followed ART-annealing, even the ultrafine grained ferrite/austenite duplex structure with about 30% austenite could be obtained af- ter long time ART-annealing in all cases. Austenization in the intercritical region （between Ad and At3） gave a duplex structure after quenching, which was nearly not affected by followed annealing process. However, high temperature austenization （above A^3） resulted in a full martensite structure after quenching, which gradually transformed into a ferrite/austenite duplex structure during the following anneal- ing process. Based on the analysis of austenite fraction and carbon concentrate, it was found that not only carbon partitioning but also manganese paxtitioning in the austenite affected the stability of austenite and even dominated the development of lamellar ferrite and austenite duplex structure during intercritical annealing with different times. At last an austenite lath nucleation and thickening model was pro- posed to describe the microstructure evolution of medium mangenese steel during ART-annealing.展开更多
Most of BN was precipitated around the spherical MnS and formed the compound of MnS and BN during the isothermal treatment at 850 ℃ after austenizing at 950-1050 ℃. Most of MnS was transformed into polygon when aust...Most of BN was precipitated around the spherical MnS and formed the compound of MnS and BN during the isothermal treatment at 850 ℃ after austenizing at 950-1050 ℃. Most of MnS was transformed into polygon when austenized at 1 150 ℃ or above, which could not be the nuclei of BN anymore. During the insulation process at 850 ℃, MnS kept the state of monomer. The compound of MnS and BN at earlier time was of fine polycrystalline in spherality and BN was formed as a plate-like monocrystal on a certain part of the polycrystalline when its dimension reached 0.6 μm.展开更多
基金supported by National Basic Research Program of China(No.G2010CB630803) National High Technical Research and Development Programme of China (Nos.2009AA03Z519 and 2009AA033401)
文摘Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrated that the initial mi- crostructures resulted from austenization at different temperatures strongly affect the microstructure evolution during followed ART-annealing, even the ultrafine grained ferrite/austenite duplex structure with about 30% austenite could be obtained af- ter long time ART-annealing in all cases. Austenization in the intercritical region （between Ad and At3） gave a duplex structure after quenching, which was nearly not affected by followed annealing process. However, high temperature austenization （above A^3） resulted in a full martensite structure after quenching, which gradually transformed into a ferrite/austenite duplex structure during the following anneal- ing process. Based on the analysis of austenite fraction and carbon concentrate, it was found that not only carbon partitioning but also manganese paxtitioning in the austenite affected the stability of austenite and even dominated the development of lamellar ferrite and austenite duplex structure during intercritical annealing with different times. At last an austenite lath nucleation and thickening model was pro- posed to describe the microstructure evolution of medium mangenese steel during ART-annealing.
文摘Most of BN was precipitated around the spherical MnS and formed the compound of MnS and BN during the isothermal treatment at 850 ℃ after austenizing at 950-1050 ℃. Most of MnS was transformed into polygon when austenized at 1 150 ℃ or above, which could not be the nuclei of BN anymore. During the insulation process at 850 ℃, MnS kept the state of monomer. The compound of MnS and BN at earlier time was of fine polycrystalline in spherality and BN was formed as a plate-like monocrystal on a certain part of the polycrystalline when its dimension reached 0.6 μm.
