Abstract
Diffusion bondings of commercial copper-beryllium alloys of Cu-0.5 mass%Be and Cu-2 mass%Be alloys to an austenitic stainless steel SUS304 were carried out in a vacuum. Ni foil and Cu foil were used as an insert metal. Influences of the bonding conditions of bonding temperature, bonding time and the insert metal on the bondability have been investigated. And also an effect of artificial agings on the joint strength of the joints has been studied. Main results obtained are as follows;
(1) On the direct bonding of copper-beryllium alloy to stainless steel, bonding was impossible when the ratio of bonding temperature to solidus temperatures of Cu-0.5 mass%Be and Cu-2 mass%Be alloys Tg/TSLwas less than 0.78 and 0.82, respectively. However, the joint strength increased abruptly with rising the ratio.
(2) The joint strength of the joints with Cu foil was higher by about 100 MPa than that of the direct bonds at the bonding condition of 830°C×3.6 ks. The tensile fracture of the joint of Cu-0.5 mass%Be alloy to SUS304 with Ni foil was occurred in the copper alloy base metal. However, the joint strength of the joint of Cu-2 mass%Be alloy to SUS304 with Ni foil was the same value as that of the direct bond because of development of voids in the diffusion layer between the copper alloy and Ni foil.
(3) When the joint of Cu-0.5 mass%Be ally to SUS304 with Cu foil or without the insert metal were aged, the joint strength was higher than that of the as-bonded, but the joint strength of the joint with Ni foil was higher value of 540 MPa. Though the direct bond of Cu-2 mass%Be alloy to SUS304 fractured at the bond interface during solution heat treatment, but the joint strength of the joint with Cu foil was higher value of 520 MPa.
