Hydrogen-assisted processing of materials

Under certain conditions, hydrogen can degrade the mechanical properties an d fracture behavior of most structural alloys; however, it also has some po sitive effects in metals. Several current and potential applications of hyd rogen for enhancing the production and processing of materials are reviewed . These include thermohydrogen processing (THP) and forming of refractory a lloys, processing of rare earth-transition metal magnets by hydrogen decrep itation (HD) and hydrogenation-decomposition-desorption-recombination (HDDR ), hydrogen-induced amorphization (HIA) and microstructural refinement, ext raction of elements from ores and alloys. and the use of hydrogen as a redu cing gas for welding and brazing. Hydrogen is found to enhance the formabil ity. microstructure and properties of a large variety of materials, includi ng steels, Ti-based alloys and metal matrix composites (MMCs), refractory m etals and alloys, rare earth-transition metal alloys, metalloid-containing metallic glasses, etc. (C) 2000 Elsevier Science S.A. All rights reserved.