Microstructure and Mechanical Properties of Ti/Cu/Fe Dissimilar Joints

The weldability of Ti/Cu/Fe trimetallic butt welds explosively bonded was investigated using the samples of different groove dimensions. The results indicated that the Ti/Cu dissimilar welds are free from cracks, and similar phase constituents are observed at Ti weld metal/Cu base metal interfaces. Cu4Ti intermetallics are formed adjacent to the Cu matrix (Cu weld metal/base metal). CuTi intermetallics with columnar structure is perpendicular to the interface and grow into the Ti weld metal. CuTi2 intermetallics show wide distribution with different morphology. Severe cracks are observed at Cu weld metal/Fe weld metal interface, attributed to the significant difference in melting point and low mutual solid solution between Fe and Cu alloys. During the solidification, it is found that liquid Cu penetrates into and weakens Fe grain boundaries. Ti weld metal near Cu matrix has a high microhardness (340 similar to 420 HV0.1). The fractography of the tensile sample confirms the quasi-cleavage fracture at Ti weld metal/Cu weld metal interface and intergranular fracture in the Fe weld metal. Possible ways to improve the welding process are also proposed.

Automated summary

The weldability of Ti/Cu/Fe trimetallic butt welds explosively bonded was investigated, and it was found that the welds were free from cracks and had similar phase constituents at the interfaces. Cu4Ti intermetallics were formed adjacent to the Cu alloy, while CuTi2 intermetallics showed a wide distribution with different morphology. Severe cracks were observed at the Cu/Fe interface, whereas quasi-cleavage fracture occurred at the Ti/Cu interface and intergranular fracture in the Fe weld metal.