【摘要】 通过扫描和透射电镜研究了铸造Ti-45Al-8Nb-0.2W-0.2B-0.02Y合金中Nb偏析区的相结构及其经中温和高温热处理后的相变规律。结果表明,铸造合金中的偏析区由约1μm大小的ωo相(B82结构)及其所在的βo(B2结构)与细小的ω相关相混杂而成的基体组成。中温较长时间处理后合金的Nb偏析区部分转变为γ相,已经发现3种βo(ω)→γ相变机制,即由基体的片层外延生长成为等轴γ、βo直接形成γ以及与已经存在的γ形成真孪晶后向βo推进。剩余偏析区表现为βo内分布着ωo或表现为纯的βo相。高温较短时间处理可以消除Nb偏析区,使偏析区由βo及ωo相关相转变为α2相。更多还原

【Abstract】 Phases and transformation behavior of Nb-microsegregation zone after heat treated at medium and high temperature of Ti-45Al-8Nb-0. 2W-0. 2B-0. 02 Y alloy were analyzed by SEM and TEM. The results show that in the as-cast alloy,the Nb-microsegregation zone is consisted of micron-level ωophase( B82structure) distributing within a blurry mixture of βo( B2 structure) and ω-related phase. After heat treatment at medium temperature for a long time,γ phase forms in parts of the Nb-microsegregation zone by three mechanics,the coarsening growth of γ lamella in lamellar colonies,directly transforming from the βophase to γ phase and forming true-twin of the preexisting γ. The retained Nb-microsegregation zone exhibits ωodistributed βoor nearly pure βo. After heat treated at high temperature,Nbmicrosegregation zone is eliminated and the original βoand ω-related phases transform to α2phase.更多还原