2007 Volume 49 Issue 166 Pages 197-202
Adhesion between two clean surfaces was investigated using a surface-activated bonding method in an ultrahigh vacuum (UHV) at room temperature. Adhesion was observed in all combinations of SUS440C/Ti-6Al-4V, INCONEL718/Ti-6Al-4V, A7075/SUS440C, SUS304/Al and INCONEL718/SUS440C. To understand the basic problems of UHV bonding, the influence of the surface roughness on bonding strength and interface structure has been studied. The surface roughness at the nanometer scale strongly influenced the bonding strength. In the case of SUS304 and Al, surfaces with less than l nm (RMS) had a high bonding strength of over 80 MPa. The interface does not have a thick reaction layer, only an amorphous layer on the order of several nanometers. Separation of the SUS304/Al interface by heat treatment has been also studied. A specimen heated at 823 K for 2 hr in a vacuum separated spontaneously without any external mechanical force. Separation occurred at the interface between the Al and the layer of the reaction products. This separation occurred only if the specimen was heated in a vacuum or argon atmosphere. The specimen did not separate when it was heated in air, nitrogen or oxygen atmospheres. The separated SUS304 could be re-bonded to Al at room temperature.