Nb对中锰TRIP钢临界退火过程中组织演变的影响

Effect of Nb on microstructure of medium-manganese trip steel during critical annealing

采用临界退火热处理工艺,利用场发射扫描电镜(FE-SEM)观察含铌和不含铌的两种热轧中锰TRIP钢在不同退火制度下的碳化物演变行为及铌对中锰TRIP钢微观组织、残留奥氏体体积分数与稳定性的影响。结果表明:试验钢经临界退火处理后获得超细晶铁素体与残留奥氏体复相组织。随着退火温度的提高,残留奥氏体体积分数出现先升高后降低的趋势;随着退火时间的延长,碳化物逐渐溶解,残留奥氏体体积分数逐渐增加,达到平衡后保持不变。Nb元素的加入可细化奥氏体晶粒,延缓碳化物溶解,推迟奥氏体转变,增加膜状奥氏体,提高奥氏体稳定性。

Carbide evolution behavior and the effects of niobium on the microstructure,retained austenite volume fraction and stability of two hot-rolled medium-manganese TRIP steels with and without niobium addition and under different intercritical annealing processes were studied by means of field emission scanning electron microscopy(FE-SEM).The results show that after the intercritical annealing treatment,an(ultrafine grained ferrite+retained austenite)dual-phase structure is obtained.With the increase of annealing temperature,the volume fraction of retained austenite first increases and then decreases;as the annealing time increases,the carbides dissolve gradually,the volume fraction of retained austenite increases gradually until equilibrium then unchanged.The Nb addition can refine austenite grains,delay carbide dissolution,delay austenite transformation,increase film austenite amount,and improve austenite stability.