TC17-TC11异种钛合金线性摩擦焊接头弯曲性能分析与改善

分析了TC11和TC17异种钛合金线性摩擦焊接接头的弯曲性能，探寻了焊缝区弯曲塑性的薄弱区。通过测试焊接接头的硬度、分析焊缝区组织、断口形貌，特别是弯曲试样表面滑移线形态，研究了弯曲断裂机制。通过焊后超声冲击以及高温固溶+时效热处理，探索了改善焊接接头弯曲塑性的工艺方法。研究结果表明，采用接头弯曲性能试验，可以更好地表征TC11和TC17异种钛合金线性摩擦焊接接头焊缝区的宏观性能；经焊后时效热处理的线性焊接头的弯曲角度只有TC17母材的38%，TC11母材的30%。弯曲塑性是其力学性能的薄弱环节；焊合区及TC17侧变形区是接头弯曲塑性的薄弱区，弯曲断口均呈脆性断裂特征。焊合区断口为细小等轴晶粒的晶间断裂，焊接界面对TC17侧的滑移有明显的阻碍作用，容易在焊合区TC17侧形成微观裂纹；TC17变形区的弯曲起裂断口是大面积滑移剪切所形成的剪切韧窝，而TC17侧变形区晶粒大而长，有利于形成更长的滑移线和更集中的位错聚集，所以弯曲试验时TC17侧变形区最容易开裂。焊后进行超声冲击处理，在试件表面形成了约20 μm厚度的变形层，接头的弯曲角度相对提高34%；接头进行高温固溶+时效处理后，接头的弯曲塑性提高，最高平均弯曲角度达到31.2°，相对提高82%。为钛合金线性摩擦焊接接头的宏观塑性性能分析与改善提出了一个有意义的研究方向。

Bending Property Analysis and Improvement of TC17-TC11 Dissimilar Titanium Alloy Linear Friction Welding Joint

The bending properties of the linear friction welded joints between TC11 and TC17 dissimilar titanium alloys was analyzed, and the weak areas of the bending plasticity of the weld zone was investigated. The mechanism of the welded joint's bending fracture was studied by hardness testing, microstructure and fracture morphology analysis. Especially, the sliding line on the bending workpiece surface was analyzed. By utilizing ultrasonic shock and high-temperature solid solution & aging heat treatment after welding, the methods that improve the bending plasticity of welded joints were explored. The results shown that the bending performance test could better characterize the macroscopic properties of the linear friction welding joints of TC11 and TC17 dissimilar titanium alloys. The bending angle of the linear friction welding joint after aging heat treatment is only 38% of the bending angle of TC17 base material and 30% of TC11 base material. It is found that bending plasticity is a weak property in the joint. The weld zone and the deformation zone on the TC17 side are the weak areas of the joint's bending plasticity, and the fracture has brittle fracture characteristics. The fracture type in the weld zone is the intergranular fracture with fine equiaxed grains. The welding interface has a significant hindrance to the slip on the TC17 side, where microscopic cracks are easily formed. The morphology of the bending fracture initiation in the deformation zone of TC17 contains shear dimples that are formed by large-area sliding shear. The grains in the TC17 side deformation zone are elongated, which prompts the formation of long slip lines and significant dislocation aggregation. Therefore, the deformation zone on the TC17 side is most likely to crack during the bending test. After implementing ultrasonic impact treatment to the welded joints, a deformation layer that is about 20 μm thick is formed on the surface of the test piece, and the bending angle of the joint increases 34%. With the high-temperature solid solution & aging treatment after welding, the bending plasticity of the joint was improved. The highest average bending angle reaches 31.2°, which represents an 82% increment. Analysis and improvement of the macroscopic plastic properties of the linear friction welded joints of the titanium alloys is represented as a significant topic of research.