Characterisation of fresh surface films formed on molten Mg-Nd alloy protected by different atmospheres

Mirak, A. R., Davidson, C. J. and Taylor, J. A. (2014). Characterisation of fresh surface films formed on molten Mg-Nd alloy protected by different atmospheres. In: Jacek Szuber, Proceedings of the 8th International Workshop on Semiconductor Surface Passivation. 8th International Workshop on Semiconductor Surface Passivation (SSP 2013), Krakow, Poland, (91-98). 08-12 September 2013. doi:10.1016/j.apsusc.2014.01.127


Author Mirak, A. R.
Davidson, C. J.
Taylor, J. A.
Title of paper Characterisation of fresh surface films formed on molten Mg-Nd alloy protected by different atmospheres
Conference name 8th International Workshop on Semiconductor Surface Passivation (SSP 2013)
Conference location Krakow, Poland
Conference dates 08-12 September 2013
Proceedings title Proceedings of the 8th International Workshop on Semiconductor Surface Passivation   Check publisher's open access policy
Journal name Applied Surface Science   Check publisher's open access policy
Place of Publication Amsterdam, Netherlands
Publisher Elsevier
Publication Year 2014
Year available 2014
Sub-type Fully published paper
DOI 10.1016/j.apsusc.2014.01.127
Open Access Status
ISSN 0169-4332
1873-5584
Editor Jacek Szuber
Volume 301
Start page 91
End page 98
Total pages 8
Collection year 2015
Language eng
Formatted Abstract/Summary
This study examines the early stages of surface oxidation of liquid Mg-3 wt%Nd under UPH argon, dry air, and air mixed with protective fluorine-bearing gases. Each of the gases were introduced as bubbles into solidifying castings. The chemistry and structure of the protective film inside the trapped bubbles were characterized by SEM and EDX analyses. Results show that due to Nd added to Mg alloy under dry air, a dense and wrinkled surface film that contains MgO and Nd2O3 are formed. Under fluorine-bearing gas mixtures, a dense and coherent surface film was found to be a mixed fluoride and oxide. For SF6, the film thickness was 50-100 nm thick while for HFC-R134a it was 35-45 nm. Needle shaped phases distributed in the Mg matrix and flake-like phases segregated on the inner bubble surface in proximity to the interdendritic regions of the alloy were both identified as Nd rich compounds. These were present under all gas conditions. The results obtained lead to a conclusion that HFC-R134a is capable of providing the most effective melt protection. The integrity and protective capability of the early surface film formation on the liquid Mg-Nd alloy was found to be significantly improved compared to pure Mg under identical gas conditions due to formation of a dense and compact MgO/Nd2O3 layer, regardless of whether fluorine species were also present.
Keyword Mg-Nd alloy
SEM
EDX
Surface films
Oxidation
Fluoridation
Protective gas
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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