ABSTRACT

Phase equilibria among the η-Fe₂Al₅ phase and its higher-ordered phases with the η framework structure were determined experimentally. The solubility range of the η phase at elevated temperature does not differ remarkably from that in previous studies, but this phase is found to undergo complicated phase transformations upon cooling. Four phases are present, namely η’, η”, η”’ and η^m, with higher-order atomic orderings in the c-axis chain sites of the orthorhombic crystal structure of the parent η phase. The η” and η”’ phases form on the Al-poor and Al-rich sides, respectively, in equilibrium with the ζ-FeAl₂ phase below ~415°C and θ-Fe₄Al₁₃ phase below ~405°C. The η’ and η^m phases become stable below 312°C and 343°C with the peritectoid reactions η’ → η^m + η”’ and η^m → η + η”, respectively. The η phase is not stable below 331°C with the eutectoid reaction of η^m + η”’ → η. On the basis of these findings, we unraveled the phase equilibria among the η-Fe₂Al₅ phase and its higher-ordered phases with the η framework structure.

摘要

通过实验确定了η -Fe ₂ Al ₅相及其具有η骨架结构的高阶相之间的相平衡。η相在高温下的溶解度范围与以前的研究没有显着差异，但是发现该相在冷却时会经历复杂的相变。存在四个相，即η ', η ”, η ”' 和η ^m，在母体η相的正交晶体结构的c轴链位中具有更高阶的原子排序。该η ”和η ''相分别在贫铝和富铝侧形成，与低于-415 °C的ζ- FeAl ₂相和低于〜405 °C的θ -Fe ₄ Al ₁₃相平衡。的η “和η^米相变得稳定低于312℃，343℃与包析反应η →交通” η^米 +  η “”和η^米→交通η  +  η ”表示。的η相不低于331℃，用稳定的共析反应η^米 +  η “”→η。基于这些发现，我们揭示了η -Fe ₂ Al ₅相及其具有η骨架结构的高阶相之间的相平衡。