Competing deformation mechanisms in ARB Cu/Nb metallic multilayers as a function of layer thickness and temperature

Competing deformation mechanisms in ARB Cu/Nb metallic multilayers as a function of layer thickness and temperature

Snel, J.S.

Van der Zwaag, S. (mentor)

Aerospace Engineering

Novel Aerospace Materials

2016-04-13

This thesis investigated the mechanical properties and deformation behaviour of accumulative roll-bonded (ARB) Cu/Nb metallic multilayers at nanoscale layer thicknesses and temperatures up to 400 degrees Celsius. Samples with individual layer thicknesses between 7 and 63 nm were nanomechanically tested at room-temperature by micropillar compression and nanoindentation at quasi-static strain-rates. Yield strength, strain-rate sensitivities and activation volumes were obtained from the experiments. First a small scale study was performed to reveal the effects of microstructural variations and pillar taper on the obtained material parameters. The deformed micropillars were then studied under the SEM to link the experimental results to observated deformation behaviour at different thicknesses. Additionally the results obtained from nanoindentation and micropillar compression were compared. Finally, based on the experimental results and observations a deformation mechanism map was proposed for the material as a function of layer thickness. Next, the high-temperature properties of the material were investigated. Micropillar compression experiments were performed in-situ inside an SEM at temperatures of 20, 200 and 400 degrees Celsius. The influence of temperature on the mechanical properties and deformation behaviour at different layer thicknesses was studied by means of the obtained material parameters and SEM observations in pillar deformation. TEM cross-sections were fabricated and analyzed to further investigate and/or confirm some of the deformation-related suspicions. The results and observations were used to draw qualitative conclusions on the high-temperature performance of the material.

multilayer
nanoscale
micropillar compression
deformation mechanisms
high temperature

http://resolver.tudelft.nl/uuid:18e7cd2a-73c6-4edc-a778-3ab9dcee834b

Student theses

master thesis

(c) 2016 Snel, J.S.