Phase transformation strengthening of high-temperature superalloys.

ABSTRACT: Decades of research has been focused on improving the high-temperature properties of nickel-based superalloys, an essential class of materials used in the hot section of jet turbine engines, allowing increased engine efficiency and reduced CO₂ emissions. Here we introduce a new 'phase-transformation strengthening' mechanism that resists high-temperature creep deformation in nickel-based superalloys, where specific alloying elements inhibit the deleterious deformation mode of nanotwinning at temperatures above 700?°C. Ultra-high-resolution structure and composition analysis via scanning transmission electron microscopy, combined with density functional theory calculations, reveals that a superalloy with higher concentrations of the elements titanium, tantalum and niobium encourage a shear-induced solid-state transformation from the ?' to ? phase along stacking faults in ?' precipitates, which would normally be the precursors of deformation twins. This nanoscale ? phase creates a low-energy structure that inhibits thickening of stacking faults into twins, leading to significant improvement in creep properties.

SUBMITTER: Smith TM 

PROVIDER: S-EPMC5121413 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature