扩散连接技术在航空航天等领域精密、复杂结构部件的生产中受到越来越多的关注，连接温度是影响部件扩散连接后使用性能的关键因素。本工作采用热压工艺制备了TC4钛合金扩散连接样品，研究了热压温度对扩散连接区显微组织、力学性能及断裂机理的影响规律。结果表明，热压过程中扩散连接界面处的合金会发生动态再结晶，温度较低时，在扩散界面处再结晶形成细小α相，随着热压温度的升高，界面处的α相逐渐粗化；动态再结晶形成的α相与合金内部非扩散区α相的尺寸存在较大差异，由此产生的晶体学失配现象会显著降低扩散界面的性能，导致热压后的合金均在扩散区发生断裂，合金延伸率较低。热处理后扩散区的组织由初生α (α_p)相、针状次生α (α_s)相和少量β相组成，随连接温度的升高，α相的尺寸逐渐增大，界面处的晶体学失配得到改善，界面迁移程度增加，合金的抗拉强度提高到998.7 MPa，延伸率提高到17.5%，达到扩散连接前TC4钛合金的性能。

Diffusion bonding has been gaining increasing attention in the manufacturing of precise and intricate structural components in aerospace and other industries. The bonding temperature is a critical factor that affects the performance of the parts produced by diffusion bonding. This study explores the impact of hot-pressing temperature on the microstructure, mechanical properties, and fracture mechanism of TC4 titanium alloy joints formed through diffusion bonding. Samples were prepared using a hot-pressing technique. The findings reveal that dynamic recrystallization occurs at the diffusion bonding interface during the process. At lower temperatures, this recrystallization results in the formation of a fine α-phase at the interface. As the hot-pressing temperature increases, the α-phase progressively coarsens. Notably, there is a substantial disparity between the size of the α-phase formed through dynamic recrystallization at the interface and that in the nondiffusion zone of the base material, leading to a crystallographic mismatch. This mismatch substantially reduces the properties at the diffusion interface and consequently leads to fracture in the diffusion-bonded joints within the bonding zone after hot pressing. In the post-heat treatment, the diffusion zone consists of primary α (α_p) phase, needle-like secondary α (α_s) phase, and β phase. Elevating the bonding temperature gradually increases the size of the α phase, thereby improving the crystallographic match at the bonding interface and facilitating interface migration. After the heat treatment at 970 ^oC, the tensile strength and elongation of the 950 ^oC diffusion-bonded TC4 Alloy joints were measured at 998.7 MPa and 17.5%, respectively, achieving the performance levels of the alloy before diffusion bonding.