Hierarchical phase separation behavior in a Ni-Si-Fe alloy
发布日期: 2020-08-18 发布者: 郑洋 阅读: 25

摘要

Improving the properties of durable high-temperature alloys is based on the fundamental understanding of the link between microstructure and three-dimensional (3D) nanochemistry. Here we utilize a complementary approach of transmission electron microscopy and atom probe tomography to link microstructure and 3D nanochemistry of a ternary single crystal Ni83.9Si13Fe3.1 (at.%) model alloy. The formation of a gamma/gamma' microstructure is revealed, containing primary and secondary gamma' precipitates analogous to Ni-based superalloys. Subsequently, microstructural hierarchy is created by the formation of gamma particles inside primary gamma' precipitates. The correlated supersaturation with gamma forming elements (Ni, Fe) of primary gamma precipitates was identified as driving force for the formation of gamma particles. The influence of aging on the mechanical properties is reported and peak hardness is achieved after 24 h of aging at 923 K. Thermo-Calc equilibrium phase concentrations based on the TTNi8 database where found to be closer to the APT data than the TCNi8 based values. Our results suggest that improved stability of gamma particles can be achieved by tailoring the phase chemistry and the lattice misfit. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.