400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 SAE TECHNICAL PAPER SERIES 980090 Bolt-Load Retention Behavior of Die-Cast AZ91D and AE42 Magnesium K.Y. Sohn, J.A. Yurko and J.W. Jones University of Michigan J.E. Kearns and J.E. Allison Ford Motor Co. International Congress and Exposition Detroit, Michigan February 23-26,1998Downloaded from SAE International by Imperial College London, Saturday, September 08, 2018The appearance of this ISSN code at the bottom of this page indicates SAE’s consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay a $7.00 per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sec- tions 107 or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Sales and Satisfaction Department. Quantity reprint rates can be obtained from the Customer Sales and Satisfaction Department. To request permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior wri tten permission of the publisher. ISSN 0148-7191 Copyright 1998 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is pu blished in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 30 0 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USAAll SAE papers, standards, and selected books are abstracted and indexed in the Global Mobility DatabaseDownloaded from SAE International by Imperial College London, Saturday, September 08, 20181980090 Bolt-Load Retention Behavior of Die-Cast AZ91D and AE42 Magnesium K.Y. Sohn, J.A. Yurko1 and J.W. Jones University of Michigan J.E. Kearns and J.E. Allison Ford Motor Co. Copyright © 1998 Society of Automotive Engineers, Inc. ABSTRACT The effect of temperature and preload on the bolt load retention (BLR) behavior of AZ91D and AE42 magne- sium die castings was investigated. The results were compared to those of 380 aluminum die castings. Test temperatures from 125 to 175°C and preloads from 7 to 28 kN were investigated. The loss of preload for AZ91D was more sensitive to temperature than that observed for AE42, especially at low preloads. In general, retained bolt-load was lowest in AZ91D. All test assemblies were preloaded at room temperature and load levels increased when the assemblies reached test temperature. The load-increase was dependent on the preload level, test temperature, alloy, and results from thermal expansion mismatch between the steel bolt and the magnesium alloy components, mitigated by the onset of primary creep. Thermal exposure (aging) of AZ91D at 150°C improved BLR behavior. INTRODUCTION The magnesium alloy AZ91 is a commonly used alloy for many industrial applications, including many automobile components. AZ91 has low density, good castability and adequate mechanical properties [1,2]. The high tempera- ture creep resistance of AZ91, however, is relatively low [3,4]. Applications subjecte