MECHANICAL CHARACTERIZATION BY DYNAMIC TENSILE LOADING OF 2017-ALUMINUM ALLOY JOINTS WELDED BY DIFFUSION BONDING

The mechanical properties of diffusion-welded joints of 2017 aluminium-copper alloys have been studied under dynamic loading with the help of a Hopkinson bar linear assembly. With the aim of comparing with previous results obtained under static loading, the strength, failure elongation and failure energy were evaluated in the welding temperature range from 475 to 600-degrees-C. Measurements of the above mechanical properties were also performed on treated specimens which were base-material specimens subjected to the same thermal cycle as the welded samples. It was found that for a welding temperature above 525-degrees-C the strength of the welded joints could reach values of the same order of magnitude as those of the treated samples. In contrast, the failure elongation and failure energy remained clearly lower, whatever the welding temperature was. For a given value of the welding pressure, the welding temperature dependence rate of the dynamic strength was shown to be increased with increasing welding time. With regard to the failure elongation or the relatively weak influence of the welding pressure on the joint strength, the spread in the experimental results (probably arising from the brittle nature of the sample failure mode) does not allow a clear conclusion. In spite of this restriction, it can be concluded that differences in the mechanical properties of the diffusion-welded joints could be evidenced by dynamic loading tests, even if no significant differences could be observed under static loading.