Hideyuki Ikeda

The Influence of Cr in Cu-Cr Alloys on the Bondability of Diffusion Bonding of Tantalum to Cu-Cr alloys

We have investigated an effect of bonding parameters on the joint strength of diffusion bonds between tantalum and copper (Case A), and between tantalum and Cu-Cr binary alloys (Case B). Main results obtained are as follows. In the case of A, it was made clear that intermetallic compounds were not formed within the bonded zone. The joint strength was increased with increasing of bonding temperature, on the bonding time of 1.8 ks and the bonding pressure of 5.6 MPa. The maximum joint strength was 275 MPa, which is equal to the tensile strength of the tantalum base metal, at bonding temperature of 1323 K on the same bonding time and pressure. The reasons why the joint strength was increased with increasing of bonding temperature or bonding pressure are decreasing of the non-bonded areas at the bonded zone. In the case of B, the joint strength was decreased when the Cr content was 0.56 at% or more in the Cu-Cr binary alloys under the bonding conditions of the bonding temperature of 1173 K, bonding time of 1.8 ks and bonding pressure of 5.6 MPa. Cr2Ta of intermetallic compound was formed within the bonded zone of the tantalum and the Cu-Cr alloy. Cr2Ta has increased controlling by diffusion rate. When the area of Cr2Ta formed within the bonded zone was 60% or less, the joint strength was equal to the tensile strength of the tantalum base metal. However, the joint strength was decreased remarkably the area of Cr2Ta was 80% on more within the bonded zone.