Nanovoid characterization of nominally pure aluminium using synchrotron small angle X-ray Scattering (SAXS) methods

Abstract

A small angle X-ray scattering (SAXS) study of nanovoids in 99.988 and 99.995 at.% aluminium is presented. Absolute intensity calibration using a glassy carbon standard is used to extract the weak SAXS signature from nanovoids introduced by thermal quenching. SAXS analysis methods, including Guinier, Porod and Indirect Transform, are used to obtain values for the void–size, number distribution and volume fraction, as well as measures of the void-metal matrix interface structure in quenched aluminium samples. The SAXS analysis has identified a residual impurity effect on void formation and has been used to characterize trends in nanovoid size, number distribution and interface structure as a function of ageing time at elevated temperatures (artificial ageing). The work presented here, including identification of experimental tools that can be readily improved, demonstrates that SAXS studies are capable of providing precise characterization of nanovoid structure in aluminium. This level of information will be useful in developing phenomenological models of void nucleation and growth capable of linking atomic scale phenomena to macroscopic material properties.

Keywords:

• nanovoids
• aluminium
• small-angle X-ray scattering
• nucleation and growth

Acknowledgements

The authors thank Prof. S. Saimoto for many helpful discussions and the Cornell High Energy Synchrotron Source (CHESS) for providing them with an excellent X-ray source, beamline instrumentation and support. CHESS is a national user facility supported by the National Science Foundation and the National Institute of Health/National Institute of General Medical Sciences under Award DMR-0225180. This work was financially supported by Queen’s University at Kingston, the Department of Physics, Engineering Physics and Astronomy, and the Natural Sciences Engineering Research Council of Canada.

Notes

1. The temperature vs. time data is used to measure the quench rate.

2. Both the pre-sample and post-sample beampaths were evacuated.

3. Note that T_sam is given by the ratio, T_sam = T_s/T_BG. Experimentally both T_s and T_BG are measured to provide a value for T_sam.

4. Note that .