Eleventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids
J. Phys. IV France 06 (1996) C8-859-C8-862
Internal Friction and Elastic Constants of Sintered TitaniumH. Ledbetter1, M. Dunn2 and S. Kim1
1 Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80303, U.S.A.
2 Center for Acoustics, Mechanics, and Materials, Mechanical Engineering Department, University of Colorado, Boulder, Colorado 80309, U.S.A.
Using a Marx-oscillator standing-wave resonance method, we measured the internal friction Q-1 of sintered titanium containing up to 26 volume-percent voids (c). The surprising Q-1-versus-c curve shape, an exponential increase, lead us to remeasure Q-1-versus-c by acoustic-resonance spectroscopy, which gave similar results. We hypothesized that both void shape and void size change with c. For the void shape, we confirmed this hypothesis by measuring longitundinal and transverse sound velocities vl and vt and comparing them with Mori-Tanaka model predictions. As c increases from 0 to 0.26, effective void shape changes from near spherical to oblate spheroidal with an aspect ratio near 0.05. Optical microscopy confirmed the void-size change. We outline a model based on wave-scattering theory that explains the observed Q-1-c behavior. Increased particle size with increased c provides the dominant factor for the exponential Q-1 increase.
© EDP Sciences 1996