Al-Cr-Mn体系的热力学模拟

摘要

In order to build up Ti-Al-Cr-Mn thermodynamical database, the Al-rich corner of the Al-Cr-Mn system in Ti-Al-Cr-Mn system was assessed by CALPHAD method. The model of stoichiometric compounds, such as Al6Mn and Al12Mn were considered as Alm(Cr, Mn)n, θ_Al7Cr, η_Al11Cr2 and μ_Al4(Cr, Mn) were modeled as Alm(Al,Cr, Mn)n. The model of T_HTAl11Mn4 and γ2_αAl8(Cr, Mn)5 were taken as (Al,Mn)29(Cr, Mn)10 and (Al,Cr)12(Al,Cr, Mn)5(Al,Cr, Mn)9,respectively. After that, a serious of thermodynamic optimization and phase diagram calculation were carried. By comparing the calculated the experimental ones, it is shown that the present calculated results are in good agreement with most of the experimental ones, however, Al8(Cr, Mn)5 compound only exists as γ2_αAls(Cr, Mn)5 formal at 1 283 K, the phase diagram of γ1_βAl8(Cr, Mn)5 is also presented. By analyzing Al-Mn system, it is found that γ1_βAls(Cr, Mn)5 is not stable at 1 283 K, η_Al11Cr2 is presented at 1 173 K where it can not be found in the experimental ones. By investigating the Al-Cr system, it is found that η_Al11Cr2 is formed by liquid+AL4Cr→Al11Cr2 at temperature below 1 204 K, so when extrapolating into Al-Cr-Mn ternary system, η_Al11Cr2 will exist stably.%为了建立Ti-Al-Cr-Mn系的热力学数据库,对该四元系中子三元系Al-Cr-Mn体系的富Al角作了热力学评估.对于该三元系中的化学计量比化合物,如Al<,6>Mn和Al<,12>Mn等采用模型Al<,m>(Cr,Mn)<,n>,θ Al<,7>Cr、η_Al<,11>Cr2及μ_Al<,4>(Cr,Mn)相选用点阵模型Al<,m>(Al,Cr,Mn)<,n>,T_HTAl<,11>Mn<,4>及γ2_aAl<,8>(Cr,Mn)<,5>相的点阵模型分别处理为(Al,Mn)<,29>(Cr,Mn)<,10>和(Al,Cr)<,12>(Al,Cr,Mn)<,5>(Al,Cr,Mn)<,9>.并对该系进行一系列热力学优化及相图计算并与相应的实验结果作了比较,发现计算结果与大部分实验结果基本吻合,但在1 283 K等温面中,Al<,8>(Cr,Mn)<,5>化合物只存在一个γ2_aAl<,8>(Cr,Mn)<,5>结构,而实验相图中还存在γ1 βAl<,8>(Cr,Mn)<,5>结构.分析Al-Mn体系认为,γ1_βAl<,8>(Cr,Mn)<,5>在1 283 K时不会稳定存在,且1173 K等温面中出现η_Al<,11>Cr2相,而实验相图中不存在该相.通过对Al-Cr系调研可以发现,η_Al<,11>Cr2相在温度下降到1204 K时通过L+Al<,4>Cr→Al<,11>Cr2生成,因此,在外推Al-Cr-Mn三元系时,η Al<,11>Cr2相在1173 K时会稳定存在.