Properties and influence of microstructure and crystal defects in Fe$_2$VAl modified by laser surface remelting

TL;DR

This study investigates how laser surface remelting affects the microstructure, grain boundaries, and electrical resistivity of Fe$_2$VAl, revealing potential for thermoelectric property manipulation through grain boundary engineering.

Contribution

It provides a detailed analysis of microstructural changes and segregation phenomena in Fe$_2$VAl after laser remelting, highlighting the impact on electrical resistivity.

Findings

Elongated grains grow nearly epitaxially within the melt pool.

Segregation of V, C, and N occurs at grain boundaries and dislocations.

Lower increase in electrical resistivity at low-angle grain boundaries suggests potential for thermoelectric optimization.

Abstract

Laser surface remelting can be used to manipulate the microstructure of cast material. Here, we present a detailed analysis of the microstructure of Fe$_2$VAl following laser surface remelting. Within the melt pool, elongated grains grow nearly epitaxially from the heat-affected zone. These grains are separated by low-angle grain boundaries with 1{\deg}-5{\deg} misorientations. Segregation of vanadium, carbon, and nitrogen at grain boundaries and dislocations is observed using atom probe tomography. The local electrical resistivity was measured by an in-situ four-point-probe technique. A smaller increase in electrical resistivity is observed at these low-angle grain boundaries compared to high-angle grain boundaries in a cast sample. This indicates that grain boundary engineering could potentially be used to manipulate thermoelectric properties.