Effect of B Content on Environmental Embrittlement of Ordered (Fe,Co)3V Alloys

The mechanical properties and environmental embrittlement of ordered (Fe,Co)(3)V alloys doped with various boron contents were investigated by tensile tests in vacuum and 1 kPa H-2. The results show that the grain size of the ordered (Fe,Co)(3)V alloy doped with 0.02wt%B decreases by 27.5% compared with boron-free (Fe,Co)(3)V alloy, while the tensile strength and elongation reach the maximum value. However, as the boron content in the ordered (Fe,Co)(3)V alloy exceeds 0.02wt%, the grain size and mechanical properties remain unchanged both in vacuum and hydrogen gas. The ordered boron-free (Fe,Co)(3)V alloy exhibits serious environment embrittlement. By adding 0.02%B the hydrogen embrittlement factor of the ordered (Fe,Co)(3)V alloy decreases by 34.4% and the fracture morphology changes from full intergranular to mixed fracture of intergranular and transgranular. But when boron content increases continuously in the ordered (Fe,Co)(3)V alloy, the hydrogen embrittlement factor keeps about 50%, indicating boron cannot completely suppress the environmental embrittlement of the ordered (Fe,Co)(3)V alloy in hydrogen.