【摘要】 对全片层Ti-45Al-8.5Nb-(W,B,Y)合金在900℃下进行长期热循环(500次和1000次)实验,采用扫描电镜(SEM)及透射电镜(TEM)研究该合金长期热循环后的显微组织不稳定性。结果表明:合金经热循环后主要产生两种类型的组织不稳定性:1)长期热循环特别是1000次热循环后,在Al偏析处易产生因晶界迁移引起的不连续粗化,随着循环次数的增加,元素扩散致使Al偏析逐渐减少;2)1000次热循环后,α2片层变细且发生断裂,这是由α2→γ相变导致的α2片层溶解所致。同时,γ晶粒在α2片层或(α2+γ)片层内部以任意方向形核。更多还原

【Abstract】 Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-(W,B,Y) alloy were investigated by SEM and TEM after long-term thermal cycling(500 and 1000 thermal cycles) at 900 °C. Two major categories of microstructure instability were produced in the alloy after the thermal cycling: 1) The discontinuous coarsening implies that grain boundary migrations are inclined to occur in the Al-segregation region after the long-term thermal cycling, especially after 1000 thermal cycles. Al-segregation can be reduced during the process of long-term thermal cycling as a result of element diffusion; 2) The α2 lamellae become thinner and are broken after 1000 thermal cycles caused by the dissolution of α2 lamellae through phase transformation of α2→γ. The γ grains nucleate within the α2 lamellae or(α2+γ) lamellae in a random direction.更多还原