TY - JOUR
T1 - Quantification of cyclic twinning-detwinning behavior during low-cycle fatigue of pure magnesium using high energy X-ray diffraction
AU - Murphy-Leonard, Aeriel D.
AU - Pagan, Darren C.
AU - Beaudoin, Armand
AU - Miller, Matthew P.
AU - Allison, John E.
N1 - Funding Information:
This work is supported by the U.S. Department of Energy , Office of Basic Energy Science, Division of Materials Science and Engineering under Award #DE-SC0008637 as part of the Center for PRedictive Integrated Structural Materials Science (PRISMS) at the University of Michigan . ADM also acknowledges the support of the National Science Foundation Fellowship. This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS) which is supported by the National Science Foundation under award DMR-1332208 . We thank Bruce Williams and CanmetMATERIALS for providing the materials for this research. We also thank Dr. Tracy Berman and Dr. Qianying Shi who assisted in the HEXD measurements. The data on which this paper was based is available on Materials Commons at https://doi.org/doi:10.13011/m3-cfgh-vh23 .
Publisher Copyright:
© 2019
PY - 2019/8
Y1 - 2019/8
N2 - The cyclic twinning and detwinning behavior of extruded Mg was investigated using in-situ high energy X-ray diffraction (HEXD) under fully-reversed low cycle fatigue conditions. Measurements were conducted at three levels of applied strain. The initial texture was such that the c-axis in most grains was perpendicular to the loading direction, an orientation in which extension twinning is favored during compressive loading. At strain amplitudes greater than 0.5%, tension-compression asymmetry was observed during cyclic loading and related to cyclic twinning and detwinning. The twinning and detwinning behavior were characterized by monitoring the evolution of X-ray diffraction peaks associated with the basal {0 0 0 2} planes throughout selected cycle. At cyclic strains greater than 0.5%, in-situ HEXD results show that twinning occurs during the compression portion of the cycle and, at early stages of fatigue, most twins are detwinned under reversed loading during the tensile portion of the cycle. It was also observed that as the number of fatigue cycles increases the twin volume fraction increases. After 100–200 fatigue cycles, the detwinning process was observed to be incomplete and a significant fraction of residual twins remained throughout an entire cycle. Using electron back scatter diffraction imaging on the surface of interrupted fatigue tests, twinning and detwinning behavior was investigated and the presence of persistent twins, including residual twins, was observed. At a lower applied strain (0.4%), twinning and tension-compression yield asymmetries associated with twinning were not observed.
AB - The cyclic twinning and detwinning behavior of extruded Mg was investigated using in-situ high energy X-ray diffraction (HEXD) under fully-reversed low cycle fatigue conditions. Measurements were conducted at three levels of applied strain. The initial texture was such that the c-axis in most grains was perpendicular to the loading direction, an orientation in which extension twinning is favored during compressive loading. At strain amplitudes greater than 0.5%, tension-compression asymmetry was observed during cyclic loading and related to cyclic twinning and detwinning. The twinning and detwinning behavior were characterized by monitoring the evolution of X-ray diffraction peaks associated with the basal {0 0 0 2} planes throughout selected cycle. At cyclic strains greater than 0.5%, in-situ HEXD results show that twinning occurs during the compression portion of the cycle and, at early stages of fatigue, most twins are detwinned under reversed loading during the tensile portion of the cycle. It was also observed that as the number of fatigue cycles increases the twin volume fraction increases. After 100–200 fatigue cycles, the detwinning process was observed to be incomplete and a significant fraction of residual twins remained throughout an entire cycle. Using electron back scatter diffraction imaging on the surface of interrupted fatigue tests, twinning and detwinning behavior was investigated and the presence of persistent twins, including residual twins, was observed. At a lower applied strain (0.4%), twinning and tension-compression yield asymmetries associated with twinning were not observed.
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U2 - 10.1016/j.ijfatigue.2019.04.011
DO - 10.1016/j.ijfatigue.2019.04.011
M3 - Article
AN - SCOPUS:85064261482
VL - 125
SP - 314
EP - 323
JO - International Journal of Fatigue
JF - International Journal of Fatigue
SN - 0142-1123
ER -