Behaviors of the Solid Phase-Bonded Interface of Poly- and Single-Crystalline Coppers

Abstract

As fusion welding is liable to accompany changes in microscopic structure and mechanical properties of the weldment, solid phase welding, especially so-called diffusion bonding with a smaller plastic deformation, has received increasing attention recently.
The object of this study is to clarify the factors that govern the bond strength and the bonding process by investigating the behaviors of the solid phase-bonded interface, including the diffusion bonding process, under the various welding conditions.
The main results obtained were as follows:
(1) The bond strength of polycrystalline copper increased with an increase in the areal fraction of welding (F) which was determined by the welding pressure, temperature and time.
(2) The F value depended also upon the initial roughness of the bonding surface and the dependency was estimated by the sintering mechanism of metal powders.
(3) Disappearance or migration of the bonded interface was not observed in as-welded conditions, but the fully bonded strength was achieved in this state. The interface changes were observed firstly after the prolonged post-weld heating.
(4) Increase of the areal fraction of welding F was detected by the electric resistance measurement of the weldment.
(5) When the direction of welding pressure was near the [110] orientation of the single-crystal specimens and the easy sliding range was large, the more compact impingement and bonding was obtained, and the interface migration by post-weld heating was accelerated.