High temperature in situ SEM assessment followed by ex situ AFM and EBSD investigation of the nucleation and early growth stages of Fe-Al intermetallics

TL;DR

This study combines in situ SEM heating with ex situ AFM and EBSD to investigate the nucleation and early growth of Fe-Al intermetallics at high temperature, revealing phase nucleation sequence and growth behavior.

Contribution

It introduces a combined in situ and ex situ microscopy approach to study intermetallic nucleation and growth stages at elevated temperatures.

Findings

{ heta}-phase nucleates first before { eta}-phase growth

Intermetallic layer initially dominated by { heta}-phase

Ex situ AFM shows shrinkage and protrusion during nucleation

Abstract

A dedicated in situ heating setup in a scanning electron microscope (SEM) followed by an ex situ atomic force microscopy (AFM) and electron backscatter diffraction (EBSD) is used to characterize the nucleation and early growth stages of Fe-Al intermetallics (IMs) at 596 {\deg}C. A location tracking is used to interpret further characterization. Ex situ AFM observations reveal a slight shrinkage and out of plane protrusion of the IM at the onset of IM nucleation followed by directional growth. The formed interfacial IM compounds were identified by ex situ EBSD. It is now clearly demonstrated that the {\theta}-phase nucleates first prior to the diffusion-controlled growth of the {\eta}-phase. The {\theta}-phase prevails the intermetallic layer.