Fe－Cr－Al合金的碳化物析出脆化及钇对脆性的影响

Carbide Precipitation Embrittlement in Fe-Cr-Al Alloys and Effects of Yttrium on Brittleness

通过力学性能测定、ＳＥＭ和ＴＥＭ分析发现，碳化物在α相晶界析出降低晶界结合强度，使Ｆｅ－（１５～２５）Ｃｒ－（４～５）Ａｌ合金严重脆化。在４７５℃时效时，此过程在１００～３００ｈ前起主导作用，时效时间超过１００～３００ｈ后，从α相均匀析出α＇相的作用增强，两个阶段的脆化特征不同。高温下晶粒长大通过降低晶粒间的协调变形能力减小合金的均匀应变。冷却过程中碳的偏聚和析出对高温脆化有更重要的贡献。Ｙ－Ｆｅ相微粒通过俘获α相中的碳消除碳的偏聚和析出、抑制４７５℃脆化和高温脆化。钇延缓α＇相析出和阻止晶粒长大的作用对抑制脆化也有贡献。

According to studies on mechanical properties and microstructures by SEM and TEM, it was indicated that, in Fe-(15～253)Cr-(4～5)Al alloys, carbids precipitation at grain boundaries held a dominat role on 475℃embrittlement before 100～300 h. After 100～300 h, role of α'-phase precipitated uniformly from α-phase matrix became dominant, and produced completely different kinetics features.The carbides precipitation, during cooling from heating temperature of specimens, also was the major factor causing high temperature embrittlement. Grain growth contribution to the embrittlement ouly through decreacing uniform deformation ability. Because the carbon atoms were captured by Y-Fe phase, the carbides precipitation would not occure in the alloys with more yttrium. That was the major reason for inhibiting 475℃embrittlement and high temperature embrittlement in these alloys. Besides, the actions of yttrium in delaying the precipitation of a'-phases and preventing the grain growth produced contributions on their anti-embrittlements too.