Low temperature damping behaviour of Ti6Al4V-SiCf composite

Internal friction and dynamic Young modulus measurements have been performed in the temperature range 80–350K 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: P1, P2 have been observed in both materials. The peak temperatures at 1 kHz are respectively 120K and 250 K. The fiber reinforced composite in the same temperature range shows a higher background damping and enhanced relaxation strength for the P1 peak. The activation energy and frequency factors evaluated from the peak temperature shift with frequency are respectively H1 = 0.21±0.02 eV, H2 = 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.