Partial pair correlation functions and viscosity of liquid Al–Si hypoeutectic alloys via high-energy X-ray diffraction experiments

Abstract

The liquid structure of Al–Si hypoeutectic binary alloys was characterized by diffraction experiments using a high-energy X-ray (synchrotron) beam source. The diffraction experiments were carried out for liquid pure Al, Al–3 wt% Si, Al–7 wt% Si, Al–10 wt% Si and Al–12.5 wt% Si alloys at several temperatures. The salient structure information such as structure factor (SF), pair distribution function (PDF), radial distribution function (RDF), coordination number (CN) and atomic packing densities (PD) were quantified as a function of Si concentration and melt temperatures. Reverse Monte Carlo (RMC) analysis was carried out using the diffraction experimental data to quantify the partial pair correlation functions, such as partial structure factor, partial pair distribution function (PPDF) and partial radial distribution function. Furthermore, the partial pair distribution function and the liquid atomic structure information were used in a semi-empirical model to evaluate the viscosity of these liquid alloys at various melt temperatures. The results show that the viscosity determined by semi-empirical methods using the atomic structure information is in good agreement with the experimentally determined viscosity values.

Keywords:

• liquid structure
• structure factor
• pair distribution function
• number density
• coordination number
• viscosity
• diffraction

Acknowledgements

This work was performed with the financial support of the Natural Science and Engineering Research Council (NSERC) of Canada and US Department of Energy (DOE) under contract number W-7405-Eng-82. The high-energy X-ray work at the MUCAT sector of the APS was supported by the US Department of Energy, Office of Science, Basic Energy Sciences under contract number W-31-109-Eng-38. Special acknowledgements are extended to Dr. Douglas Robinson, beam line scientist at Sector 6-ID-D, Advanced Photon Source, Argonne, IL, USA, for his cooperation and support in performing the liquid diffraction experiments. The authors gratefully acknowledge the financial support of General Motors Corporation, specifically the contribution from Dr. Michael J Walker and Dr. Carlton Fuerst.

Notes

Notes

1. http://www.isis.rl.ac.uk/RMC/downloads/useful.htm

2. RMCA v.3.14 program, http://wwwisis2.isis.rl.ac.uk/RMC/rmc.htm

3. General Electric Corporation, Schenectady, New York, USA.