Effect of hydrogen on high temperature flow behavior of near a-Ti alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 679; p. 75
• Main Authors: Babu, SM Jagadeesh, Kashyap, BP, Prabhu, N, Kapoor, R, Singh, RN, Chakravartty, JK
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier BV 02.01.2017
• Subjects: Beta phase; Compression tests; Concentration (composition); Deformation; Deformation mechanisms; Dislocation mobility; Grain boundaries; Grain boundary sliding; Grain size; High temperature; Hydrogen; Strain rate; Strain rate sensitivity; Titanium base alloys; Yield strength
• ISSN: 0921-5093; 1873-4936

The effect of hydrogen on high temperature flow behavior of VT20, a near α-Ti alloy, was studied using differential strain rate compression tests. Hydrogen level was varied from 0.0015 to 0.36 wt%. Strain rate jump tests were carried out over the strain rate and temperature ranges of 10-3-10-1 s-1 and 600-947 °C, respectively. The addition of hydrogen increased the volume fraction of β phase, decreased the grain size and lowered the flow stress up to test temperature of 900 °C. The values of apparent strain rate sensitivity (m) and activation energy for deformation (Q) were found to vary from 0.03 to 0.46 and 176-382 kJ/mol, respectively, depending on strain rate, test temperature and hydrogen level. With increasing hydrogen content the peak strain rate sensitivity shifted to lower temperatures. The values obtained for m (≥0.30) and Q (~176 kJ/mol) suggested that the deformation mechanism is the grain boundary sliding accommodated by lattice diffusion. The lower values of m (0.20-0.25) suggested dislocation climb as the deformation mechanism and the further decrease in m and increase in Q suggested power law breakdown.