FeCrAl不锈钢的平衡凝固相变与析出行为

Phase transformations and precipitation behavior in FeCrAl stainless steel during equilibrium solidification

借助Thermo-calc软件对FeCrAl不锈钢所属的Fe-(18~21)Cr-(3~5)Al-(0~0.03)C-(0~0.2)Si-(0~0.2)Mn多元体系在凝固过程中的相变及析出行为进行了研究.采用Thermo-calc中TCFE7数据库对该体系的垂直截面图进行计算,分析了不同组元对凝固和冷却过程中相变的影响,并得到FeCrAl不锈钢的平衡凝固相变路径图.结果表明FeCrAl不锈钢由1600℃平衡冷却至300℃的过程中完整的平衡相变路径为:L→AlN+αδFe→AlN+αδFe+Cr_7C_3→AlN+αδFe+Cr_7C_3+Cr_(23)C_6→AlN+αδFe+Cr_(23)C_6→AlN+αδFe+Cr_(23)C_6+σ→AlN+αδFe+Cr_(23)C_6+σ+α'→AlN+αδFe+Cr_(23)C_6+α'.凝固过程中Cr_7C_3与σ相是否析出分别取决于体系中C、Si含量;Al含量的提高可扩大αδFe+Cr_7C_3的稳定区,降低α'相的析出温度,抑制σ相的析出;Cr含量的提高可以减小αδFe+Cr_7C_3的稳定区,扩大σ相和α'相的稳定区.

The phase transformations and precipitation behavior were investigated by using Thermo-Calc software in the Fe- （ 18-21 ） Cr-（ 3- 5 ） Al- （ 0-0.03 ） C- （0-0.2 ） Si- （ 0-0. 2 ） M n multicomponent system relevant to FeCrAl stainless steel during solidification. The vertical sections of this system were calculated by using the TCFE7 database. Based on these vertical sections, the influence of different elements was analyzed in the phase transformations during solidification and a diagram of the phase-transformation path of FeCrAl stainless steel was obtained during equilibrium solidification. The results indicate that the full-phase transformation path of FeCrAl stainless steel during the cooling process from 1600 ℃ to 300℃ is as follows：L→AlN＋αδFe→AlN＋αδFe＋Cr7C3→AlN＋αδFe＋Cr7C3＋Cr（23）C6→AlN＋αδFe＋Cr（23）C6→AlN＋αδFe＋Cr（23）C6＋σ→AlN＋αδFe＋Cr（23）C6＋σ＋α＇→AlN＋αδFe＋Cr（23）C6＋α＇. The precipitation of Cr7C3 and σ, during the solidification process mainly depends on the carbon and silicon contents in the system, respectively. Increasing the aluminum content can enlarge the stable region of αδFe＋Cr7C3 , lower the precipitation temperature of α＇, and restrain σ precipitation. Increasing the chromium content can reduce the stable region of αδFe＋Cr7C3 and enlarge the stable region of σ and α＇.