Hardening evolution of AZ31B Mg sheet |
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Authors: | X.Y. Lou M. Li R.K. Boger S.R. Agnew R.H. Wagoner |
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Affiliation: | 1. Department of Materials Science and Engineering, The Ohio State University, 477 Watts Hall, 2041 College Road, Columbus, OH 43210, USA;2. Abaqus Central, Inc., 1440 Innovation Place, W. Lafayette, IN 47906-1000, USA;3. Department of Materials Science and Engineering, University of Virginia, 116 Engineer’s Way, P.O. Box 400745, Charlottesville, VA 22904, USA |
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Abstract: | The monotonic and cyclic mechanical behavior of O-temper AZ31B Mg sheet was measured in large-strain tension/compression and simple shear. Metallography, acoustic emission (AE), and texture measurements revealed twinning during in-plane compression and untwinning upon subsequent tension, producing asymmetric yield and hardening evolution. A working model of deformation mechanisms consistent with the results and with the literature was constructed on the basis of predominantly basal slip for initial tension, twinning for initial compression, and untwinning for tension following compression. The activation stress for twinning is larger than that for untwinning, presumably because of the need for nucleation. Increased accumulated hardening increases the twin nucleation stress, but has little effect on the untwinning stress. Multiple-cycle deformation tends to saturate, with larger strain cycles saturating more slowly. A novel analysis based on saturated cycling was used to estimate the relative magnitude of hardening effects related to twinning. For a 4% strain range, the obstacle strength of twins to slip is 3 MPa, approximately 1/3 the magnitude of textural hardening caused by twin formation (10 MPa). The difference in activation stress of twinning versus untwinning (11 MPa) is of the same magnitude as textural hardening. |
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Keywords: | Magnesium alloy Tension/compression testing Simple shear testing Texture Acoustic emission Plastic deformation Slip Twinning Untwinning |
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