高Nb-TiAl合金连续升温过程的组织演变

Microstructure evolutions of high Nb-TiAl during continuous heating process

采用光学显微镜(OM)、扫描电子显微镜(SEM)、X线衍射仪(XRD)、差热分析仪(DSC)和热膨胀仪(DIL)等研究高Nb-TiAl合金(Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y,摩尔分数,%)在连续升温过程中的相变行为与显微组织演变。结果表明:高Nb-TiAl合金在升温过程中存在2个相变过程,1有序α2相→无序α相转变,2四方γ相→α相扩散型转变;在α2相→α相转变结束后,γ相→α相转变开始前,显微组织的近片层团尺寸随温度升高而减小,板条间距随温度升高而增大;随着温度的逐渐升高,γ相在母相α相的晶界、边界处逐渐消失。

Phase transformation and microstructure evolutions of Ti-45Al-8. 5Nb-0. 2W-0. 2B-0. 02 Y alloy during continuous heating were investigated using optical microscopy（ OM）,scanning electron microscopy（ SEM）,X-ray diffraction（ XRD）,differential scanning calorimetry（ DSC）,and dilatometry（ DIL）.Results indicate that two phase transformations were taken place during continuous heating process：ordered α2→disorder α and tetragonal γ→α. After α2transferred to α and before γ transferred to α,the near lamellar colonies decreased with the temperature increasing and the spacing size between laths increased with the temperature increasing.Meanwhile,with temperature increasing,γ phase disappeared on the grain boundaries and edges of parent α phase.