Effects of Hydrogen and Metal-hydride on Mechanical Properties in TiAl Intermetallic Compounds.

It is well known that intermetallic compounds are embrittled by exposuring to the hydrogen environment. However, there are only a few reports investigating the effects of hydrogen-embrittlement on TiAl intermetallic compounds. In this study, the effects of hydrogen and metal-hydride on mechanical properties in TiAl intermetallic compounds were investigated. Hydrogen was introduced to specimens by corroded in acidic solution, and a metal-hydride formed on the specimen surface was analyzed by an X-ray diffraction method. To dissolve the metal-hydride, some specimens were heat -treated at 623 K in vacuum. Some mechanical properties—fracture stress, fracture strain, hardness and so on—were compared by using with or without corrosion and heat-treated specimen. Also, the hydrogen microprint technique was applied to visualize the behavior of hydrogen in TiAl. It is found that fracture strength and fracture strain were decreased by effects of hydrogen. Also silver grains indicating hydrogen emanation were revealed along slip lines and around crack tips.