Ti2 AlNb 合金可以长时间在650~750℃条件下工作，具有高比强度、良好的室温断裂韧性和良好的抗蠕变 性等，被认为是最具应用潜力的高温轻质金属材料。 为研究在不同热处理制度下O相形核和长大过程，探索显微组织演化规 律和O相变体选择行为，采用包套轧制工艺作为加工方法，轧制材料名义成分为Ti-22Al-24Nb-0.5Mo(原子分数，%)。通 过轧制得到厚度为1mm的Ti2 AlNb合金板材。 对轧制后板材进行固溶时效处理后，O相大量析出；随着时效温度的提 高，O相板条越来越粗大，同时O相析出量先增加后减少，在930℃时O相析出体积分数达到最高，为52%。 在该热处 理制度下O相形核析出方式既有界面不稳定形核也有感生形核，但是O相在晶界附近的形核析出方式更多倾向于感生 形核，界面不稳定形核得到的O相数量上较少。 轧板在1000℃固溶、815℃时效以及920℃固溶、800℃时效这两种热处理 之后，得到的组织均为双态组织，轧制后的固溶时效过程基本没有对O相变体的析出造成影响。

Ti2 AlNb alloys can operate for extended periods at temperatures between 650 and 750 ℃, offering high specific strength, excellent room-temperature fracture toughness, and good creep resistance. These properties make Ti2 AlNb alloys one of the most promising lightweight metallic materials for high-temperature applications. The alloy sheets, with a final thickness of 1 mm, were produced via a clad rolling process, employing a nominal composition of Ti-22Al-24Nb-0.5Mo (at.%) as the rolling material. After the rolled sheets were subjected to solution aging treatment, a significant amount of O-phase precipitated. As the aging temperature increases, the O-phase lamellae grow coarser, and the amount of precipitated O-phase initially increases but then decreases. At 930 ℃, the volume fraction of the precipitated O-phase reaches its maximum value of 52%. Under this heat treatment regime, the nucleation mechanisms for O-phase precipitation include both interfacial instability nucleation and induced nucleation. However, near grain boundaries, the O-phase tends to nucleate and precipitate predominantly through induced nucleation, with fewer O-phase particles forming through interfacial instability nucleation. Following solution treatment at 1 000 ℃ and aging at 815 ℃, as well as solution treatment at 920 ℃ and aging at 800 ℃, the resulting microstructures are bimodal. The solution aging process after rolling has little effect on the precipitation of O-phase variants.