Surface dislocations in a Fe₂VAl Heusler alloy: Formation and effects on electrical resistivity

Dislocation density impacts functional properties of materials. For hard materials, introducing dislocations is normally challenging due to crack formation. Here, we use mechanical grinding and nanoindentation techniques to form near-surface dislocations in Fe₂VAl. Transmission electron microscopy shows that 2 × 10¹⁴ and 3 × 10¹³ m^-2 are present at 1 μm away from the surface, respectively. Local four-point probe electrical measurements indicate that the electrical resistivities for pristine, indented, and ground regions are 3.9, 4.2, and 7.5 ± 0.1 μΩ cm, respectively, confirming that dislocations significantly impede charge transport. The relation between resistivity and dislocation density is discussed in terms of the interaction between electrons and the strain fields induced by dislocations. Additionally, we determine that the elastic modulus and nanohardness for the pristine alloy are 225 ± 5 GPa and 6.6 ± 0.1 GPa, respectively. This study demonstrates that surface mechanical treatments can be used to control the electrical resistivity of these alloys.