Experimental Study of Interfacial Contacting Process Controlled by Power Law Creep

Interfacial contacting processes under a high temperature and a high bonding pressure (T = 973 K, P = 30 MPa) are experimentally studied, using oxygen free copper. The faying surfaces were machined by lathe, resulting in controlled regular surface asperities. The asperity angle of surface ridges was changed from 10 to 60 deg. The change in the interfacial deformation mode with the asperity angle has been investigated. Results show the interfacial contact process is strongly influenced by the asperity angle (shape of surface ridge). The bonding tests were carried out in high vacuum atmosphere (10−4 Pa) so that the surface oxide film need not be considered. Experimental results are in good agreement with the results calculated by a finite element model, in which the interfacial contact is assumed to be produced by power law creep alone. It was thus suggested that void coalescence is governed by power law creep under the present test conditions (T = 973 K and P = 30 MPa) except for the final stage of bonding. Experimental results also suggest that the elementary rate process of interfacial contact due to power law creep is classified into two types; surface folding and interfacial expansion. Here, the surface folding is the phenomenon that two faying surfaces are overlapped to each other and the interfacial expansion means that the bonded interface area is extended along the bond-interface.