# Effect of Annealing on Vacancy-Type Defects and Heterogeneous Cu Precipitation Behavior in Fe60Cr12Mn8Cu15Mo3V2 Alloy

## TL;DR

This paper studies how annealing affects defects and copper precipitation in a complex alloy, using advanced spectroscopy and microscopy techniques.

## Contribution

The study reveals the temperature-dependent behavior of vacancy clusters and Cu precipitates in a multi-principal element alloy.

## Key findings

- Annealing at 773 K reduces Cu precipitate size to ~33 nm with increased density.
- Vacancy clusters form at 573 K and dissociate at 673 K, reaching equilibrium between 773–973 K.
- The alloy maintains a dual-phase BCC and FCC structure during thermal processing.

## Abstract

This study systematically investigates the evolution of vacancy-type defects and heterogeneous Cu nanoprecipitates in an Fe60Cr12Mn8Cu15Mo3V2 (at%) multi-principal element alloy during thermal processing, utilizing Positron annihilation lifetime spectroscopy (PAS), coincidence Doppler broadening (CDB) spectroscopy, and transmission electron microscopy (TEM). The results show that the alloy exhibited a dual-phase coexistence structure of Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC). The CDB results show that the density of heterogeneous Cu precipitates gradually increases with annealing temperature. Compared to the as-cast alloy, the precipitates annealed at 773 K exhibit a significantly reduced size (approximately 33 nm) with higher density. The PAS results demonstrate that gradual migration and aggregation of monovacancies at 573 K form vacancy clusters, while contraction and dissociation of these clusters dominate at 673 K. Within the temperature range of 773–973 K, the dynamic equilibrium between the aggregation and decomposition of vacancy clusters maintains stable annihilation characteristics with minimal lifetime changes.