Recent research activities in materials science indicate a clear trend towards heterostructured materials as they are a promising material class because of their superior properties compared to conventional materials [1]. In particular, their multi-layered architecture provides the opportunity to combine metals with completely different mechanical, thermal or electrical properties and use the composite sheet material for a variety of applications. To obtain a sufficient quantity of material for larger applications and tailor the resulting laminated metal composites (LMCs) the so-called accumulative roll bonding (ARB) process is in favor. The achievable layer thicknesses start at several mm and can reach down to just a few nm, while the sequence of the neighboring layers can be tailored easily by changing the initial stacking sequence. Nevertheless, there is still a lack of understanding of how and to which extent the interfaces between two neighboring sheets affect the overall mechanical properties.

In the present work, copper-based LMCs were produced by a maximum of ten ARB cycles resulting in a layer thickness range from ~280 µm down to ~50 nm as the overall sheet thickness remains constant during the entire production process. Intermediate heat treatments after two ARB cycles lead to a layered but intermediately recrystallized microstructure which is necessary to get equally deformed materials that only differ in the interface density. Micro-yielding tensile loading-unloading-reloading (LUR) tests were performed on the ARB-processed laminate materials as well as on monolithic copper material processed accordingly. As shown in previously published work by the authors, the amount of inelastic back-strain in monolithic materials strongly depends on the grain size [2]. In this study, we observed an additional effect in laminated metal composites, where the inelastic back-strain scales with the interface density. This new method allows quantifying the interface-related co-deformation effects in heterogeneous LMCs and their hardening contribution during plastic straining, as it is exemplarily shown for the AA5005/AA5754 system [3].

References

[1] Y. Zhu, X. Wu, Heterostructured materials, 2023, Progress in Materials Science 131.

[2] H. Mughrabi, H. W. Höppel, M. Kautz, R. Z. Valiev, Annealing treatments to enhance thermal and mechanical stability of ultrafine-grained metals produced by severe plastic deformation, 2003, Z. Metallkd. 94, 1079-1083.

[3] P. M. Pohl, M. Kuglstatter, M. Göken, H. W. Höppel, Quantifying co-deformation effects in metallic laminates by loading-unloading-reloading tensile tests, to be published