Joining of Nano- and Microstructured Metals
Doctoral Student:
Majid Ramezani Goldyani, Stevens Institute of Technology, USA, mramezan(at)stevens.edu
PI/Project Lead:
Marcus Rutner, Hamburg University of Technology, Germany, marcus.rutner(at)tuhh.de
Collaborator:
Michael Demkowicz, Massachusetts Institute of Technology, USA, demkowicz(at)mit.edu
Multilayered metal nanocomposites have gained interest in science and industry due to their unique properties. Enhanced properties of these nanocomposites compared to conventional metallic materials, such as radiation damage resistance, electrical and magnetic properties, strength and indentation hardness, ductility, and fatigue resistance, make them attractive for novel applications. An essential step towards industrial usage of multilayered nanocomposites is to be able to joining them. However, conventional joining processes cause localized heating around the joint and may compromise the integrity of the nanolayered composite cross section. In this research, Cu-Nb multilayered nanocomposites are synthesized by dc magnetron sputtering at room temperature on Si substrate. Various joining processes are introduced and performed and the advantages and drawbacks in regard to the processing and the nanomechanics of the joint are discussed. The nanostructure of the sputter-deposited Cu-Nb joint zone and adjacent heat affected zone is investigated by Scanning Electron Microscope imaging. Further, the hardness and strength of the joint area is studied by Atomic Force Microscopy. Findings of this research have been published Scripta Materialia (please refer to my recent publications).
Photo right by City University of New York
The first metal joining method of nanostructured metal composites has been introduced in a recent Scripta Materialia article.
Metal nanolaminate coatings are introduced as a new approach in post-weld treatment methods. A Cu/Ni nanolaminate coating is electrodeposited from a single Cu/Ni citrate bath onto a butt-welded tension-tension fatigue specimen. The nanolaminate coating consists of a Ni base layer and 160 alternating Cu and Ni layers. The specimen is tested in tension-tension fatigue with a stress range close to the yield strength of the specimen. This first study reveals surprisingly high lifetime extensions of welded joints. The tested specimens are examined using FIB/SEM and TEM. Local roughness measurements are carried out with AFM. This leads to observations on crack behavior of nanostructured Cu/Ni multilayers. The Cu layers show initial multi-crack formation, while the cracks arrest at the Cu/Ni interfaces. The Ni layers bridge those cracks and each Ni layer tears individually. Hypotheses are formed on the fatigue behaviour of Cu/Ni multilayers.
