Environmental embrittlement of two-phase Fe30Ni20Mn35Al15

It is shown that the ductility of lamellae-structured Fe₃₀Ni₂₀Mn₃₅Al₁₅ (in at. %), which consists of B2 and f.c.c. phases, is influenced by testing environment. Tensile tests performed in air at strain rates ranging from 3 × 10^?6 to 3 × 10^?1 s^?1 showed that the elongation to fracture and ultimate tensile strength (UTS) increased with increasing strain rates below 3 × 10^?3 s^?1, and were independent of strain rate at ～10.5% and 840 MPa for strain rates ≥ 3 × 10^?3 s^?1. In order to understand this strain-rate sensitive behavior, tensile tests were also performed in either dry oxygen or 4% hydrogen + nitrogen at different strain rates. The elongation and UTS in oxygen were insensitive to strain rate and close to those tested at 3 × 10^?3 s^?1 in air, whereas the elongation in hydrogen was 4% for strain rates ≤3 × 10^?3 s^?1 and increased to ～10.8% at 3 × 10^?1 s^?1. The reduction of ductility in air and hydrogen-charged environment at low strain rate is attributed to hydrogen embrittlement.