钛合金的初始α片层组织特征对其热机械加工过程中的显微组织演化及力学性能具有重要影响，掌握初始α片层组织演化规律是实现钛合金微观组织和力学性能精准调控的前提条件。本工作通过中断炉冷热处理方法研究了Ti6246钛合金β→α相转变过程中初始α片层组织的演变规律，分析了晶界α相(α_GB)的生长行为及其对后续晶内α片层生长、微织构强度的影响。结果表明，钛合金由β单相区缓冷至α + β两相区的过程中，与两侧β晶粒都符合Burgers取向关系(BOR)的α_GB (2-BOR α_GB)优先在β晶界处形核。而后，与2-BOR α_GB取向相近的晶内α片层在α_GB处形核并向两侧β晶粒内生长，2-BOR α_GB与两侧α片层在晶界处形成较强的微织构。在α相生长早期，两侧β晶粒与2-BOR α_GB的BOR偏差越小，较强的微织构形成越早。除2-BOR α_GB优先发生β→α相转变外，与单侧β晶粒符合BOR的α_GB (1-BOR α_GB)也形核生长，但是，与1-BOR α_GB取向相近的晶内α片层仅在符合BOR的单侧β晶粒内形成，而在另一侧β晶粒中则形成取向不同的晶内α片层，在晶界处形成较弱的微织构。

The initial lamellar microstructure of titanium alloys significantly affects their microstructural evolution and mechanical property during thermo-mechanical treatments. Thus, the evolution of the initial lamellar microstructure must be explored to control the microstructure and enhance the mechanical property. The present work focuses on the evolution of the lamellar microstructure during β→α phase transformation via interrupted furnace cooling experiments to analyze the growth behavior of the grain boundary α phase (α_GB) and its effect on the subsequent growth of intragranular α lamellae and microtexture. Results show that when titanium alloy furnace cools from the β phase field to the α + β phase field, the α_GB holding Burgers orientation relationship (BOR) with both sides of β grains (2-BOR α_GB) has an advantage for early transformation at the β grain boundary. In particular, type II (49.5°/<110>) and type III (60°/<110>) β grain boundaries are preferential sites for the early nucleation of α_GB particles. As the temperature decreases, α lamellae holding similar orientation to 2-BOR α_GB grow to both sides of β grains. Thus, 2-BOR α_GB and both sides of α lamellae form a strong microtexture at the grain boundary. At the early growth period of the α phase, the smaller the θ_2-BOR (misorientation of the close-oriented α_GB variant pair of parents β1 and β2) of 2-BOR α_GB, the earlier the formation of a strong microtexture at the grain boundary. 2-BOR α_GB preferentially precipitates, whereas the α_GB holding BOR with only one side of the β grain (1-BOR α_GB) nucleates. α lamellae holding a similar orientation to 1-BOR α_GB grow to one side of the BOR-β grain (holding BOR with α_GB), whereas α lamellae with a different orientation grow in the non-BOR-β grain. Thus, 1-BOR α_GB and one side of α lamellae form a weak microtexture at the grain boundary.