2018 Volume 59 Issue 4 Pages 538-545
The multi-component alloy Nb-20Si-23Ti-6Al-3Cr-4Hf was produced by powder injection molding or hot isostatic pressing of pre-alloyed, gas-atomized powder. The resulting microstructure comprises the Nb solid solution as well as the α- and γ-modifications of Nb5Si3. Creep is evaluated in constant true stress tests at 1000 and 1100 ℃. The analysis of the creep behavior regarding its dependence on microstructural and testing parameters such as grain size, stress, and temperature reveals grain boundary sliding as the prevalent deformation mechanism. This is backed up by SEM/EBSD and TEM observations in the undeformed and deformed state. This creep mechanism was found to be a direct result of the small grain/phase sizes after powder metallurgical processing and led to a creep resistance even lower than that of a single-phase niobium-based alloy.
