Influence of hydrogen on microstructure and mechanical properties of alloys based on Ni3Al

The hydrogen-induced effect on mechanical properties, fracture features and on deformation structures in intermetallic alloys based on Ni3Al was studied. Four different sets of tensile specimens were prepared: binary, binary and charged by hydrogen, B and Zr-doped and B and Zr-doped and charged by hydrogen. Hydrogen was introduced at 800degreesC in flowing hydrogen. The tensile tests were performed at room temperature and at strain rate of 5.8 x 10(-5) s(-1). Yield strength of the binary specimens exhibited increase of 38% due to hydrogen effect and ultimate tensile strength decreased by 19%. A similar trend of the hydrogen effect was observed for B and Zr-doped alloys. The yield stress increased by 8% and the tensile strength decreased by 26%. The fracture features and the dislocation structures resulting from scanning electron microscopy (SEM) and TEM observations, respectively, were affected by the presence of hydrogen in binary and B and Zr-doped alloys. Macroscopic and microscopic strengthening effects of hydrogen are discussed. (C) 2004 Elsevier B.V. All rights reserved.