Gas Entrapment and Evolution in Aluminium Alloys Produced by Powder Metallurgy

摘要

Part of a comprehensive research program involving different aspects of degassingof powder metallurgy (PM) aluminum alloys is presented. Some fundamentals concerning gas entrapment and evolution such as the relationship between surface composition and chemical reactions are presented. A fundamental semiquantitive description of the degassing process based on thermodynamical and kinetic considerations is given. The consolidation processing of the Al-Si-X PM aluminum alloys is shown to require a degassing step which improves room and elevated temperature properties of the final product. The conventional degassing process was improved by the development of a vacuum degassing process in combination with a flushing procedure using argon or nitrogen; degassing of Al-20Si-X is shown to give products with superior properties. The research concerned rapidly solidified Al-20Si-X aluminum, compressed in vaccum tight containers (cans) with temperatures of the PM compact during evacuation and flushing chosen up to 550 C.