Evaluation of microstructures in alloys having a macroscopic composition gradient

Abstract

In the macroscopic composition gradient (MCG) method, it is important to ensure that the MCG itself does not influence the phase transformation and microstructure behavior of the MCG alloy. The following two points should be theoretically and experimentally assessed to (1) ensure that the macroscopic composition profile is unchanged during aging at the lower temperature and (2) clarify the influence of the MCG on phase transformation, as it may influence microstructure formation even if the MCG profile does not change during aging. On the basis of experimental and theoretical investigations, 10 at. %/µm is considered the maximum composition gradient which does not influence microstructure formation.

Keywords:

• macroscopic composition gradient
• phase field method
• phase decomposition
• phase stability
• phase transformations
• solid-state transformation

Acknowledgement

The authors thank Dr. T. Koyama of NIMS Japan and Professor T. Kozakai of Nagoya Institute of Technology for useful discussions.