针对α/β型TC18钛合金大型锻棒中心与边部的性能差异, 利用EBSD技术研究了β相的组织差异、织构差异及形变程度差异, 并考察了β相的这些差异对遵循Burgers关系的α_p相取向及球化速率的影响. 结果表明, 锻态TC18钛合金中的β相处于不同程度的形变状态, 随位置不同而具有不同的织构, 中心位置β相具有再结晶织构<100>的特点, 并且存在显著的晶粒尺寸不均匀性, 这些因素对中心与边部的性能差异有主要贡献. α_p相的球化过程主要在β相晶内亚晶界上完成, 前期随形貌由片状向方块状的变化, 取向关系变化很小; 后期向球形过渡时, 取向关系偏差较大. β相晶粒内的取向差是衡量加工硬化对强度贡献的有效参数, 而α/β两相的取向关系与理想Burgers关系的偏差是揭示球化速度和形变β相晶粒回复程度的有效参数.

To understand the differences in the mechanical properties between the center and surface regions of large size forged TC18 titanium alloy bar, electron backscatter diffraction (EBSD) technique is applied to reveal the differences in textures and strains in β phase in addition to the microstructures observation. The influence of the states of β phase on the deviation to the Burgers orientation relationship (OR) between α/β phases is also analyzed according to the acquired EBSD information. It is found that the β phases in different positions of forged bar are in different states of strain, textures and grain sizes. The β phase in the center shows strong <100> texture and coarse and inhomogeneous grain sizes which all contribute to the difference in properties. The spheroidization of α_p phase proceeded mainly within β grains at subgrain boundaries and the OR between two phases changed slightly as the lamella α_p phase transforms into block-like α_p phase, but changed strongly during transforming to globular morphology. The misorientation in β phase is an effective parameter to evaluate the contribution of work-hardening state for the enhancement of strength, whereas the level of the deviation to Burgers OR is an effective parameter to evaluate the spheroidizing rate and the recovery extent.