Microstructure and hydrogen permeability in Nb-TiFe alloys

Abstract The relationship between the microstructure and hydrogen permeability of Nb–TiFe alloys is investigated. The fully eutectic alloy, which consisted of the bcc-(Nb, Ti) and B2-TiFe phases, is found in the Nb 16 Ti 53 Fe 31 composition. The alloys formed between the Fe 50 Ti 50 and Nb 16 Ti 53 Fe 31 compositions, expressed as (Ti 50 Fe 50 ) 1− x (Nb 16 Ti 53 Fe 31 ) x , consist of the eutectic structure, including the primary TiFe phase for x x  > 1. The volume fraction of the primary phase is decreased (0  x x  > 1) with increasing x . The alloys with 0.4  x 12 Ti 52 Fe 36 alloy with 60 vol% of the primary FeTi phase exhibits a high hydrogen permeability of 2.9 × 10 −8  molH 2 /m/s/Pa 0.5 at 673 K without hydrogen embrittlement. The formation of hydrogen permeable Nb–TiFe alloys is possible at higher Ti content and lower Nb content than those of the Nb–TiNi and Nb–TiCo alloys.