Effect of pressure on microstructure and mechanical properties of diffusion bonded joints of Ti2AlNb alloy

Abstract

Direct solid diffusion bonding of Ti2AlNb alloy was carried out, and the effect of pressure on the microstructure and mechanical properties of the bonded joints was studied. Scanning electron microscopy was used to analyze the microstructure of the welded joint under different pressures. The tensile property of the joints with different pressures was tested and the variation trend of the tensile property with pressure was analyzed. The results show that with the increase of pressure, the deformation within the sample surface layer increased, and the dynamic recovery and recrystallization occurred in the deformed area at high temperature, which promotes the closing of voids on the bonding interface and the rise of well-bonded areas. A diffusion bonded joint of Ti2AlNb alloy can be divided into three parts：recrystallization zone, deformation zone and base metal. The recrystallization zone is mainly composed of equiaxed B2 phase and α2 phase. With the increase of pressure, the width of the recrystallization zone becomes wider obviously, and the strength of the bonded joint increases first and then decreases. When the welding parameters are 960 ℃-60 MPa-120 min, the welded joint had the best performance, and its tensile strength is 972 MPa, reaching 98% of the base metal. An excessive pressure coarsened the recrystallization grains, and cracks appeared at the interface of the recrystallized zone and the deformation zone, which deteriorated the performance of the bonded joint.

Keywords

• ti2alnb alloy
• diffusion bonding
• microstructure
• mechanical properties