Ni/Al-Hybrid Cellular Foams: An Interface Study by Combination of 3D-Phase Morphology Imaging, Microbeam Fracture Mechanics and In Situ Synchrotron Stress Analysis.

Jutta Luksch,Christoph Genzel,Patrick Gruenewald,Manuela Klaus,Florian Schaefer,Anne Jung,Frank Mücklich,Christoph Pauly,Christian Motz,Ralf Derr,Marc Laub

doi:10.3390/ma14133473

Abstract

Nickel(Ni)/aluminium(Al) hybrid foams are Al base foams coated with Ni by electrodeposition. Hybrid foams offer an enhanced energy absorption capacity. To ensure a good adhering Ni coating, necessary for a shear resistant interface, the influence of a chemical pre-treatment of the base foam was investigated by a combination of an interface morphology analysis by focused ion beam (FIB) tomography and in situ mechanical testing. The critical energy for interfacial decohesion from these microbending fracture tests in the scanning electron microscope (SEM) were contrasted to and the results validated by depth-resolved measurements of the evolving stresses in the Ni coating during three-point bending tests at the energy-dispersive diffraction (EDDI) beamline at the synchrotron BESSY II. Such a multi-method assessment of the interface decohesion resistance with respect to the interface morphology provides a reliable investigation strategy for further improvement of the interface morphology.

Highlights

Our results clearly underline that a pre-treatment of the Al base foam before the electrodeposition of the Ni coating improves the strength of the connection at the interface, the shear stiffness of the interface and the bending and buckling strength of the individual struts on the microscale of a foam, resulting in an increased strength and energy absorption capacity for the macroscopic foams
Energy-dispersive X-ray diffraction (XRD) in the synchrotron allowed us to measure the stress depth distribution in the Ni coating of a Ni/Al hybrid foam and revealed residual compressive stresses before and a slightly reduced in-plane tensile stress perpendicular to the bending axis during in situ three-point bending near the Ni/Al interface
During the in situ test the moment of the interface decohesion was measured as a decrease in the stress accommodated in the Ni layer that is followed by a small plateau prior to fracture of the coating as seen in most specimens (Figure 8)

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Foams are bio-inspired, cellular and lightweight materials that offer a unique energy absorption capacity e.g., as crash energy absorber [1,2,3,4] or as catalyst supports [5]. Hybrid foams belong to the group of composite foams and are characterized by a combination of different materials. Typical hybrid foams are copper (Cu)/Al hybrid foams [6,7,8] and

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