Ti2AlNb superalloy consisting of O-phase and B-phase often exhibits deformation heterogeneity and incompatibility due to the mechanical characteristics of phases. To study the size and distribution effects of the O-phase on the fracture properties of Ti2AlNb superalloy, three types of material with different O-phase sizes and distributions were prepared through heat treatments, and the tensile properties of the heat-treatment samples were investigated. An image-based crystal plasticity model was built based on the backscattered electron images of the superalloy to probe the effects of O-phase size and distribution on stress, strain partitioning, and fracture. The strain hardening and fracture behaviors were discussed in terms of the strain partitioning between O-phase and B-phase, and the formation and propagation of micro-cracks, respectively, by combining the simulation and experimental results. Simulation results show the stress and strain partitioning between O/B phase interfaces increases with the increase of O-phase size, and micro-cracks are formed when the local stress concentration exceeds the critical value. The presence of micro-cracks imposes high shear stress on the neighboring B-phase matrix and promotes fast crack propagation through the B-phase matrix, resulting in cleavage fracture. Inversely, micro-cracks tips can be alleviated when the stress concentration at O/B phase interfaces can be relaxed by the plastic deformation of the B-phase matrix. The variation of stress and strain partitioning with deformation during plastic deformation shows that strain partitioning isn't related to O-phase size, but stress partitioning depends on it. Thus, the effects of O-phase size on fracture mainly depend on stress partitioning. This paper presents a meaningful method to model the phase distribution, and the effects of O-phase size and distribution on stress, strain partitioning, and fracture behavior are studied.

由于相的机械特性，由O相和B相组成的Ti2AlNb高温合金经常表现出变形异质性和不相容性。为了研究O相的尺寸和分布对Ti2AlNb高温合金断裂性能的影响，通过热处理制备了三种O相尺寸和分布不同的材料，并对热处理样品的拉伸性能进行了研究。 。基于超合金的反向散射电子图像，建立了基于图像的晶体可塑性模型，以研究O相尺寸和分布对应力，应变分配和断裂的影响。分别从O相和B相之间的应变分配以及微裂纹的形成和传播方面讨论了应变硬化和断裂行为，通过结合仿真和实验结果。仿真结果表明，随着O相尺寸的增大，O / B相界面之间的应力和应变分配增加，当局部应力集中超过临界值时，会形成微裂纹。微裂纹的存在会在相邻的B相基体上施加高剪切应力，并促进裂纹通过B相基体的快速传播，从而导致解理断裂。相反，当通过B相基质的塑性变形可以放松O / B相界面处的应力集中时，可以缓解微裂纹尖端。塑性变形过程中应力和应变分配随变形的变化表明，应变分配与O相尺寸无关，而应力分配取决于它。从而，O相尺寸对断裂的影响主要取决于应力分配。本文提出了一种有意义的建模相分布的方法，并研究了O相尺寸和分布对应力，应变分配和断裂行为的影响。