Investigation on the interfacial microstructure and mechanical properties of the W-Cu joints fabricated by hot explosive welding

The welding of thick W onto Cu, with good bonding, has been a big challenge due to the large differences in physical properties between W and Cu. Among various novel methods, explosive welding is the promising one to produce bimetals with large size and great thickness. However, the cracking of brittle W under high strain rate limits its application. In this work, hot-explosive welding technique was explored to overcome this problem. A 2 mm thick W plate was preheated to 500 celcius and was successfully welded with pure Cu plate, without any cracks formed in W layer. The result suggests that preheating W to over its dynamic ductile-to-brittle transition temperature and decreasing the imported kinetic energy are two most important factors for the successful welding of thick W plate. The weldability window calculated using the parameters at 500 degrees C predicted the formation of a good wavy interface. The microstructures at W-Cu interface were characterized by optical microscope, SEM, EBSD and TEM. The mechanically mixed W-Cu phase and the 2 similar to 6 nm thick amorphous layer along the interface created strong bonding between the immiscible W and Cu. The measured interfacial compressive shear strength reached 188 MPa, indicating a good bonding strength of the interface.

Automated summary

This study focuses on the application of hot-explosive welding technique to address the challenges in welding W onto Cu. The results suggest that preheating W above its dynamic ductile-to-brittle transition temperature and reducing the input kinetic energy are two key factors for successful welding of thick W plates. The formation of mechanically mixed W-Cu phases and a few nanometers thick amorphous layer along the interface enhanced the bonding strength between W and Cu.