The Influence of Time, Atmosphere and Surface Roughness on the Interface Strength and Microstructure of AA6061–AA1050 Diffusion Bonded Components

Abstract

Diffusion bonding experiments followed by tensile testing were conducted on cylindrical pairs of AA6061–AA1050 aluminum alloys. The influence of bonding time, atmosphere and surface roughness on the resulting interface strength was studied. Metallurgical characterization was performed to study the quality of the bonded interface for different process conditions, and also to investigate the process of oxide formation on the specimen surface. Finite element analysis of the bonding experiments was used to study the thermo-mechanical fields during the bonding process. Using a cohesive zone approach for modelling the bonded interface, the bond strength for the different process parameters was quantified. The results demonstrate that high bond strength can be obtained even for specimens bonded in an air furnace, provided the surface roughness is low. When the surface roughness increases, specimens bonded in air show a reduction in interface strength, which is not observed for specimens bonded in vacuum. Inspection of the bonded interface suggests that this reduction in interface strength can be attributed to oxidation and pockets of air trapped between the asperities of the contact surface, which hinder diffusion and plastic flow.

A Study of Interface Bond Strength Following Hot Deformation Bonding of AA6061 at Different Temperatures and Loading Rates

“…The temperature and strain rate dependent flow stress for the Al6061 was determined from the hot compression experiments as will be discussed in the next section. The Taylor-Quinney coefficient was taken as 𝜂 = 0.9 while the thermal and properties of AA6061 were taken from [6]. The steel rams were defined as rigid bodies since they do not experience notable deformation compared to the specimens.…”

“…The time required for generating a mechanical bonding is short but generally results in a weak interface bond strength compared to metallurgical bonding. On the other hand, metallurgical bonding commonly requires a long dwelling time at the specific temperature due to the time required for diffusion processes between the layers to take place [6]. One promising method for obtaining a strong metallurgical bond in short time scales is joining by hot plastic deformation [7][8][9][10].…”