Dislocation Driven Chromium Precipitation in Fe-9Cr Binary Alloy: A Positron Lifetime Study

TL;DR

This study investigates how initial heat treatment affects chromium precipitation in Fe-9Cr alloy, revealing dislocations as key to Cr precipitation through positron lifetime and microscopy analyses.

Contribution

It demonstrates that dislocations drive Cr precipitation in Fe-9Cr alloy, using positron lifetime measurements combined with TEM and EDS analysis.

Findings

Dislocations promote Cr precipitation during annealing.

Cr precipitates are fine, around 4 nm, and Cr-enriched.

Positron lifetime increases correspond to Cr precipitation stage.

Abstract

The influence of initial heat treatment on anomalous Cr precipitation within high temperature solubility region in Fe-9Cr alloy has been investigated using positron lifetime studies. Air-quenched samples with pre-existing dislocations exhibited a distinct annealing stage in positron lifetime between 800 and 1100 K corresponding to Cr-precipitation. During this stage, Transmission Electron Microscopy showed fine precipitates of average size 4 nm, dispersed throughout the sample and from EDS analysis they are found to be Cr-enriched. The existence of dislocations is found to be responsible for Cr precipitation.