4th International Conference on Advances in Solidification Processes
8-11th July 2014, Beaumont Estates, Old Windsor, UK

Prof Lars Arnberg - NTNU, Norway

Lars Arnberg
LARS ARNBERG received his doctorate degree in Inorganic Chemistry from Stockholm University in 1979. After spending 2 years as a post doc at MIT, he was hired by the Swedish Institute of Metals Research where he conducted research on powder metallurgy and rapid solidification technology and managed a research department. In 1990 Lars Arnberg was appointed a Professor of Metallurgy at the Norwegian University of Science and Technology. His main field of research and teaching is solidification and casting of metals, particularly light metals. This research includes fundamental studies of crystal nucleation and growth as well as studies of casting defects and process technology. Lars Arnberg has a wide international network; he has research cooperation with leading groups in the area of solidification in Europe, USA, Australia and Asia. He has more than 250 publications and has received national and international rewards for his research.

Abstract

Influence on trace element on the microstructure of Al-Si foundry alloys

Thomas Hartmut Ludwig1, Paul Louis Schaffer2 and Lars Arnberg1

1Norwegian University of Science and Technology, Norway
2Hydro Aluminium, Norway

Recent estimates predict a decrease of the quality of raw materials for aluminium production and an increased use of scrap metal in primary metal production. Therefore higher levels of trace elements must be tolerated in future aluminium alloys, including Al-Si foundry alloys. The present paper presents investigations of the influence of calcium, phosphorous, nickel and vanadium on the microstructure of hypoeutectic Al-Si foundry alloys.

It has been found that phosphorous in concentrations down to 3 ppm form aluminium phosphide particles (AlP) that nucleate eutectic silicon very efficiently at low undercooling and therefore has a major influence on the Al-Si eutectic microstructure – eutectic silicon forms coarse plates at low undercooling. Calcium in amounts exceeding 40 ppm form the intermetallic phase Al2Si2Ca that nucleates on the aluminium phosphides and deactivates the phosphides, preventing them from nucleating eutectic silicon resulting in a reduction of the eutectic temperature and a refinement of the Al-Si eutectic. Calcium does not, however, cause a flake-to-fibrous transition (chemical modification) of the eutectic silicon.

Nickel partitions into the Al3Ni phase, which is well distributed in the Al-Si eutectic and forms a close system with the eutectic Si. In commercial Al-Si alloys where Fe is present, Ni partitions into the Al9FeNi phase.

Vanadium also dissolves into the Fe-rich phases of commercial Al-Si alloys. Traces of V were found in β-Al5FeSi and α-Al8Fe2Si phases. When the V-concentration exceeded 0.2 wt%, most of the vanadium formed a pre-eutectic polyhedral Si2V phase.