New Characteristics and Bonding Mechanisms of the Directly Bonded W/Cu Plates

Directly bonded W/Cu plates find important applications in fields such as nuclear fusion reactors. However, the bonding process is difficult because W and Cu do not react nor form solid solutions with each other at any temperatures. In the current work, W/Cu bonded plates without any intermediate layer materials were successfully fabricated by hot pressing. The maximum shear strength of the prepared W/Cu plates was τ = 137.2 MPa. A large amount of WO_x crystal grains (1–2 μm in size) were formed in situ on the bonded interface of W plates. The WO_x grains and W protrusions formed on the W plates were embedded in Cu plates, which was the most important factor contributing to the bonding strength of the W/Cu bonded plates. The shearing and breaking process of the W/Cu bonded plates included three stages: stage I corresponded to the plastic deformation of Cu; stage II mainly included cutting and sliding friction occurring on the bonded interface of Cu; and breaking of W protrusions, debonding of WO_x grains, and tearing of Cu occurred in stage III.