微合金钢中碳化物在奥氏体和铁素体中的沉淀析出动力学研究

Study on the precipitation kinetics of carbides in austenite and ferrite of microalloyed steels

根据多元复合析出相的固溶热力学计算和经典形核长大动力学理论,研究了Ti-Mo、Ti-Nb-Mo和Ti-NbMo-V复合微合金化钢中碳化物在奥氏体(γ)和铁素体(α)中沉淀析出规律。研究表明,在γ区,Ti-Mo钢中析出相主要为富Ti的(Ti,Mo)C粒子,在较高温度区间,Ti-Nb-Mo和Ti-Nb-Mo-V钢中主要析出富Ti富Nb的碳化物粒子。在α区,Ti-Mo和Ti-Nb-Mo钢中析出相主要为富Mo的碳化物粒子,Ti-Nb-Mo-V钢主要析出富V的碳化物粒子。Ti-Mo、Ti-Nb-Mo钢中析出相在γ中沉淀析出的PTT曲线和NrT曲线分别呈“C”和反“C”形,而(Ti,Nb,Mo,V)C在奥氏体中沉淀析出NrT曲线呈反“ε”形,随着温度降低开始析出时间先缩短后延长。(Ti,Nb,Mo,V)C在高温奥氏体区形核速率最快,(Ti,Nb,Mo)C次之,(Ti,Mo)C最慢,且对应形核的最快析出温度依次升高。在铁素体区,(Ti,Mo)C和(Ti,Nb,Mo)C的PTT曲线和NrT曲线分别呈现“ε”形和反“ε”形。Ti-Nb-Mo-V钢中碳化物在整个铁素体区的形核速率快于Ti-Mo和Ti-Nb-Mo钢。

According to the solid solution thermodynamic calculation of the multi-composite precipitated phases and the classical nucleation growth kinetic theory,the deposition and precipitation of carbides in austenite(γ)and ferrite(α)phases in Ti-Mo,Ti-Nb-Mo and Ti-Nb-Mo-V composite microalloyed-steels were studied.It is shown that inγphase,the precipitates in Ti-Mo steel are mainly Tienriched(Ti,Mo)C particles.In the higher temperature range,Ti-Nb-Mo and Ti-Nb-Mo-V steels mainly precipitate carbide particles enriched in Ti and Nb.In the ferritic zone,the precipitates in Ti-Mo and Ti-Nb-Mo steels are mainly Mo-enriched carbide particles,while in Ti-Nb-Mo-V steel,V-enriched carbide particles are mainly precipitated.The PTT and NrT curves of the precipitated phases in Ti-Mo and Ti-Nb-Mo steels show"C"and reverse"C"shapes,respectively,while the NrT curves of(Ti,Nb,Mo,V)C precipitated in austenite show reverse shapes"ε".As the temperature decreases,the precipitation time first decreases and then prolongs.The nucleation rate of(Ti,Nb,Mo,V)C is the fastest in the high-temperature austenitic zone,followed by(Ti,Nb,Mo)C,and that of(Ti,Mo)C is the slowest.The corresponding fastest nucleation precipitation temperature increases in sequence.In the ferritic region,the PTT and NrT curves of(Ti,Mo)C and(Ti,Nb,Mo)C are presented"ε"form and reverse"ε"shape,respectively.The nucleation rate of carbides in Ti-Nb-Mo-V steel is faster in the entire ferritic zone than in Ti-Mo and Ti-Nb-Mo steels.