In the present work, β-phase formation along grain boundaries has been evaluated by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) analysis methods. The thickness of β-phase along grain boundaries, measured by STEM for a 1-year thermally treated sample, was estimated to be 15 - 20 nm. Etching effects of phosphoric acid solution and ammonium persulfate solution on the Al matrix are discussed. The effect of ASTM G67 nitric acid attack on different surfaces was investigated. Mass loss data was collected for several AA5xxx alloys using long-term (~ 12 months), constant temperature (40 to 70°C) exposure tests. Other samples were treated in thermal exposure furnaces with cyclic temperatures (40 to 45°C and 50 to 70°C) to represent the heating cycles in service conditions.

Subject
Metal surfaces, Mass loss, Thickness measurement, Magnesium alloys, Ammonium, Nitric acid, Heat, Sensitization, Phosphoric acid, Aluminum alloys, Grain boundary, Alloys, Samples
Keywords:
STEM, EDS, sensitization, β-phase, ASTM G67
© 2012 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2012
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.