电子束焊接QCr0.8/TC4焊缝反应层结构及成长分析

QCr0.8/TC4偏铜电子束焊接焊缝由熔合区及反应层组成,其中反应层的组织结构、相组成和反应程度是影响接头抗拉强度的主要因素.参考扩散理论,利用Fick第一定律计算了稳态扩散时Cu,Ti两种组元在界面处的扩散通量比.反应层中优先生成CuTi化合物,其在反应层中为连续生成及分布.通过能谱分析得出反应层的组成依次为Cu CuxTi区,CuTi基固溶体区.其中CuxTi为多种化合物的混合,如Cu4Ti,Cu3Ti,Cu2Ti等.由于电子束焊接接头冷却速度极快,TC4侧靠近熔合线处来不及生成第二相化合物,因此反应层处形成的连续金属间化合物CuTi层使该处变得硬脆且残余应力较大,成为影响接头力学性能的主要因素.

Analysis of structure and growth of QCr0.8/TC4 welded reaction layer by electron beam welding

QCr0.8/TC4 electron beam welding seam was composed of fusion zone and reaction layer, and the structure, phase composition and extent of reaction played important part in the joint tensile strength.According to the Fick diffusion law, the ratio of elements Cu and Ti diffusion flux can be calculated.In the reaction layer, CuTi was generated firstly, which was continuous and distributed in the reaction layer.The energy spectrum analysis indicated that the reaction layer composition was Cu +Cu_xTi zone and CuTi based solid solution zone.And CuxTi was the mixture of several compounds, such as Cu₄Ti, Cu₃Ti, and Cu₂Ti and so on.Due to the rapid cooling, The zone near TC4 fusion line couldn''t generate the second phase compound in the weld.Therefore, the continuous intermetallic compound CuTi rusulted in high residual stress and hard brittle layer, which was the main factor effecting the joint mechanical properties.