Abstract
This work investigates two nominally similar polycrystalline alloys, with a subtle difference in Nb content, intended to elucidate its effect on local phase transformationLocal phase transformation strengthening during high temperature creepCreep. Tests were conducted at 750 °C and 600 MPa to target the creep regime dominated by superlattice intrinsic and extrinsic stacking faults, as well as microtwinning. Alloy A, with higher Nb and lower Al, was found to be superior in creep strength to Alloy B, with lower Nb and higher Al, as well as previously investigated ME3 and LSHR. Atomic resolution scanning transmission electron microscopy and energy-dispersive spectroscopy found that this increased creep strength was due to a novel local phase transformation occurring along microtwinMicrotwin boundary interfaces as a result of the Nb increase. Complementary density functional theory calculations helped to confirm that this was χ phase formation. It is hypothesized that this transformation was the cause of the increased creepCreep strength exhibited by Alloy A.
Published Version
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