High temperature deformation behavior of melt hydrogenated (TiB + TiC)/Ti-6Al-4V composites

Ti-6Al-4V matrix composites with 5 vol% TiB and TiC particles were in situ synthesized in this study. Hydrogen was added into the composites directly by melting the composites in gas mixture of hydrogen and argon (Melt Hydrogenation Technology). Microstructure observation results showed that hydrogen addition changed the distribution of ceramic particles to near network structure. The effect of microstructure, deforming temperature, strain rate and hydrogen content on high temperature compressive behavior were investigated. Thermal simulation results of high temperature compression at same strain rate indicated that hydrogen addition caused softening effect at higher deforming temperature and hardening effect at lower temperature, competition of the dominant effect was decided by distribution of ceramic particles and microstructure of matrix. Experimental results of hot compression at same deforming temperature and increasing strain rate indicated that moderate hydrogen content decreased the peak stress and improved the hot workability of composites. Microstructure observation of as compressed composites indicated that hydrogen eliminated defects and encouraged the dynamic recrystallization (DRX) after hot compression, the mechanism of hydrogen induced improvement of DRX, and relationship among hydrogen content, dislocations density and percentage of DRX were discussed. (C) 2017 Elsevier Ltd. All rights reserved.