Microstructure and thermomechanical behavior of Heusler phase Ni2AlHf-strengthened NiAl-Cr(Co) alloy produced by HIP of plasma-spheroidized powder

摘要: Abstract This study demonstrates that homogeneous high-purity micropowders with grain size of 10–45 µm from refractory NiAl-Cr(Co)-Hf alloy can be produced by combustion elemental synthesis and further treated in a thermal plasma flow. The optimal parameters spheroidization the synthesized powders are shown at which resulting spherical particles characterized high sphericity (~ 98%) absence satellites or internal porosity. were consolidated HIP. structure was investigated scanning electron microscopy (SEM) high-resolution transmission (HRTEM). fine features segregation hardening nanoparticles Ni2AlHf (the Heusler phase) hafnium solid solution (ssHf) NiAl matrix thoroughly studied. Furthermore, situ examination structural phase transformations occurring as-HIP NiAl-based carried out upon heating temperature range 25–850 °C. α-Cr formed inside grains via two different mechanisms: (1) spinodal decomposition 250–450 °C Guinier-Preston zone rich Cr its subsequent transformation into precipitates 25–170 nm size; (2) heterogeneous nucleation growth nanocrystallites 7–40 nm long on prismatic dislocation loops 750–850 °C. thermomechanical properties studied 596–1100 °C Gleeble System 3800 testing system. correlation between load high-temperature creep rate, as well dependences Young's modulus (E), offset yield strength (σ0.2), rate sensitivity coefficient (m), ascertained. ultimate tensile strength, σ0.2, proportional limit being examined during uniaxial compression test cylindrical sample 750 °C true strain ~ 0.01 s−1 137.8 GPa, 682, 455 358 MPa, respectively.