钎焊间隙对B-Ti57CuZrNi钎料钎焊TC4钛合金接头组织和高温力学性能的影响

Effect of Brazing Gap on Microstructure and High Temperature Mechanical Properties of TC4 Titanium Alloy Joint Brazed With B-Ti57CuZrNi Solder

采用B-Ti57CuZrNi钎料对TC4钛合金进行了930℃,30 min不同钎焊间隙下的对焊钎焊,研究了钎焊间隙对接头微观组织和高温力学性能的影响。结果表明,随钎焊间隙增大,接头缺陷增加,钎焊间隙<0.1 mm时焊缝填充较好,接头宏观无明显缺陷。0.06~0.30 mm间隙的钎缝组织为铸态组织,原基体界面存在一个大于30μm的扩散层,得到了有效的冶金结合。随钎焊间隙增大,钎缝整体宽度增加,钎缝铸态组织更明显,高温拉伸强度降低。钎焊间隙>0.1 mm时钎焊接头高温拉伸断裂均出现在焊缝,高温拉伸强度低于基体的,断裂形式为脆性断裂,而钎焊间隙<0.1mm时高温拉伸强度则高于基体的。从获得钎焊接头优良的400℃拉伸性能来考虑,钎焊间隙应<0.1 mm。

The butt brazing tests at 930 ℃ for 30 min of TC4 titanium alloy were carried out by using B-Ti57CuZrNi solder under different brazing gaps. The effects of the brazing gap on the microstructure and high temperature mechanical properties of the joints were investigated. The results show that the joint defects increase with the increase of the brazing gap.The good weld filling with no obvious defects is observed when the brazing gap is less than 0.1 mm. The microstructure of the brazing joint presents the characteristic of cast structure when the brazing gap is of 0.06-0.30 mm, and the diffusion layer with thickness bigger than 30 μm exists at the original interface, and effective metallurgical bonding is obtained. With the increase of the brazing gap, the width of the brazing seam increases, the cast microstructure of the brazing joint is more obvious, and the high temperature tensile strength decreases. When the brazing gap is bigger than 0.1mm, the high temperature tensile fracture of the brazed joint occurs in the weld. The high temperature tensile strength of the joint is lower than that of the matrix, and the fracture belongs to brittle fracture. When the brazing gap is less than 0.1mm, the high temperature tensile strength of the joint is higher than that of the matrix. Considering from obtaining good 400 ℃ tensile properties of the brazed joint, the brazing gap should be less than 0.1mm.