Enhanced Performance Near Net Shape Titanium Alloys by Thermohydrogen Processing

摘要

This research program was aimed at a detailed understanding of the effect of hydrogen as a temporary alloying element (thermohydrogen processing, THP) on processing parameters, microstructural modifications and final mechanical properties of cast- and-wrought (ingot metallurgy), powder metallurgy and cast titanium alloys. Fundamental results have been obtained which can now be used to develop optimum THP steps to refine the microstructure and improve the mechanical properties of titanium alloys. As a part of this project, the phase diagram of the Ti-6Al-4V - hydrogen system, and a determination of the stable and metastable phases, which occur in this system, have been defined. Kinetics of the beta phase decomposition has been studied and the non- equilibrium TTT (temperature-time-transformation) diagrams of the beta to alpha+beta+hydride transformation have been determined for the alloys with 10, 20, and 30 at.% hydrogen. Kinetics of decomposition of martensite structures have also been determined for these three hydrogen concentrations. The results have been presented at international meetings, twenty-two technical papers were published and twelve papers have been submitted for publication. Additionally a patent was also awarded. The results of the work have been transitioned to an Army SBIR program designed to produce low cost titanium components for armored vehicles.