An electron microscopy study of tweed microstructures and premartensitic effects in high damping 53Cu45Mn2A1 alloy
Mayes, Larry Leroy
Perkins, A.J. (Jeff)
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The evolution of tweed microstructure upon aging a 53Cu45Mn2Al alloy was studied in the transmission electron microscope (TEM). Characteristic (110) tweed contrast develops after the alloy is aged for 4 hours or longer at 400 C, which apparently is just within the miscibility gap, and is then cooled to room temperature. The microstructure evolved is proposed to consist of a small proportion of Mn-rich regions in a Cu-rich matrix. As the phase separation proceeds, the Neel temperature and the FCC-to-FCT transition temperature both rise within these Mn-rich domains, and as a result they begin to display incipient lattice instabilities when observed at room temperature. This takes the form of a 'flickering' effect in the TEM image. The flickering consists of consistent and repetitive contrast variations at specific locations in the microstructure. The significance of these microstructural features to damping is discussed.
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