Hydrogen effects in (AlTi)SiC particle metal matrix composites

The development of advanced air frames and propulsion systems has generated significant research and development activity in the area of light-weight high temperature intermetallic alloys. Exposure to hydrogen results in the severe embrittlement of many intermetallics. In the present study the microstructure of spray-atomized and codeposited metal matrix composites (MMCs) were characterized following hydrogen charging. The results show that, under severe conditions such as exposure to NaCl solutions at cathodic charging conditions, initial crack propagation in (AlTi)SiC_p MMCs (which SiC_p represents SiC particles) occurs without any applied stress. It is also important to note that hydrogen charging increases the amount of hydrogen in the material. There is always the possibility of preferential hydrogen accumulation at the large number of incoherent interfaces between the reinforcement particulates and the matrix. The phenomenology of hydrogen embrittlement and possible mechanisms of embrittlement are discussed.