Low temperature anelasticity in Ti6Al4V alloy and Ti6Al4V-SiCf composite

Internal friction and dynamic Young modulus measurements have been performed in the temperature range 80-350 K on the Ti6Al4V alloy and a Ti6Al4V-SiCf composite reinforced by unidirectional SiC fibers (SCS-6). A vibrating reed apparatus operating at low strain amplitude (<10(-5)) in the frequency range 10(2)-10(4) Hz was employed. Two anelastic relaxation peaks: P-1, P-2 have been observed in both materials. The peak temperatures at 1 kHz are respectively 120 K and 250 K. The fiber reinforced composite in the same temperature range shows a higher background damping and enhanced relaxation strength for the P-1 peak. The activation energy and frequency factors evaluated from the peak temperature shift with frequency are respectively H-1 = 0.21 +/- 0.02 eV, H-2 = 0.50 +/- 0.03 eV and tau(-1)(01) = 10(15) s(-1), tau(-1)(02) = 10(12) s(-1). Both peaks position and relaxation strength depend on hydrogen content and the relative amount of defects in alpha and beta phases. (C) 2009 Elsevier B.V. All rights reserved.