Thermomechanical properties and the deformation mechanism of nickel monoaluminide-based alloys produced by L-PBF in combination with gasostatic treatment and aging

Abstract

The synthesized NiAl-based material was manufactured by laser powder bed fusion (L-PBF) followed by gasostatic treatment and aging using spheroidized CompoNiAl-M6 (NiAl–8Cr–6Co–1Nb-0.9Hf) alloy powder (the 20–50 μm fraction). The structure was examined by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED); nanoparticles of the refractory phases were identified. The compressive mechanical properties of the alloy were measured at 20, 800, 900, and 1000 °C. Doping with niobium and hafnium was shown to strengthen the alloy with fine-grained Laves and Heusler phases, as well as the (HfxNby)C carbide phase, which reduce the size of NiAl grains and prevent grain boundary diffusion. Due to this fact, the material can be used at temperatures above 800 °C. Ultimate compressive strength (σb) at 900 °C was 575 MPa, while being 260 MPa at 1000 °C. The dislocation substructure of the deformed sample was examined, and the predominant deformation mechanisms (dislocation glide, dislocation climb, and shear of the crystal lattice of the matrix phase) were identified. In situ TEM nanotensile testing revealed that fine-grained refractory phases increase σb from 1360 MPa to 1870 MPa. Clusters and agglomerates of strengthening phases act as stress concentrators and cause premature alloy failure because of stress localization at the particle interface.