Development of Ultrahigh-Strength,Ductile Titanium Alloys by Thermomechanical Processing and Transformation-Induced Plasticity.

摘要

This report summarizes the results obtained during the third year of a program aimed at the development of high strength titanium alloys showing enhanced ductility and toughness due to the occurrence of deformation-induced phase transformation. Binary alloys of titanium with the beta-eutectoid solutes iron,manganese,and chromium were investigated during the first half of this program. The second half of the program was devoted to an investigation of the deformation-induced transformation behavior and mechanical properties of alloys based on Transage 129 (Ti-2Al-11V-2Sn-11Zr). Marked transformation-induced plasticity (TRIP) behavior was observed for the experimental alloys in a beta-annealed condition,especially when the V:Al content ratio was reduced below 5.5. When the alloys were aged to increase the yield strength the TRIP behavior disappeared,although deformation-induced transformation still occurred in some instances. The reasons for this behavior are discussed in the report and it is concluded that a high yield strength and TRIP behavior are mutually exclusive in these alloys,since both depend on the same strengthening mechanism. (Modified author abstract)