电子束焊热作用对DD407单晶熔凝区裂纹形成的影响

使用电子束焊对DD407单晶高温合金进行焊接，采用光学显微镜和扫描电镜观察分析了熔凝区裂纹形态及分布特征，采用EDS测定了试样枝晶干与枝晶间区域的化学成分，计算了元素的偏析比并分析了裂纹形成原因。结果表明：在电子束热作用下，DD407单晶熔凝区中主要产生纵向裂纹、横向裂纹、弧坑裂纹、晶间裂纹，当其它工艺参数不变时，熔凝区凝固裂纹含量随着电子束流的增大而先增大后减小；DD407单晶在焊接凝固过程中，杂晶区合金元素偏析严重，导致低熔点共晶组织聚集并形成低熔点液态薄膜，在凝固收缩拉应力作用下，使得杂晶区常形成凝固裂纹。

Effect of electron beam welding thermal on crack formation in fused region of single crystal superalloys DD407

Nickle base single crystal superalloys DD407 were welded by electron beam welding. the morphology and distribution of crack were analyzed by optical microscopy and scanning electron microscopy. the chemical component between dendrite dry and interdendritic area was measured by EDS. the segregation ration of elements was calculated and the causes of crack formation was analyzed. The results show that: longitudinal cracks, transverse cracks, crater cracks, intergranular cracks mainly were produced in fused region of DD407 under the thermal effect of the electron beam. With the increasing of electron beam current, the content of solidification cracks increase firstly and then decrease when other parameters remain unchanged. low melting point eutectics gather and form a low-melting liquid films due to the serious segregation of alloying elements in miscellaneous grain zone,thus the solidification cracks are often formed in miscellaneous grain zone in the solidification shrinkage tensile stress.