Site Occupancy and Lattice Parameters in Sigma-Phase Co-Cr alloys

TL;DR

This study uses neutron diffraction to analyze atom distribution and lattice parameters in sigma-phase Co-Cr alloys, revealing site occupancy preferences and temperature-dependent lattice changes.

Contribution

It provides detailed insights into atom site occupancy and lattice parameter variations in sigma-phase Co-Cr alloys across different compositions and temperatures.

Findings

All five lattice sites are occupied by both Co and Cr atoms.

Sites A and D are mainly occupied by Co, while B, C, and E by Cr.

Lattice parameters increase with Cr content and temperature.

Abstract

Neutron diffraction technique was used to study distribution of Co and Cr atoms over different lattice sites as well as lattice paramaters in sigma-phase Co100-xCrx compounds with x = 57.0, 62.7 and 65.8. From the diffractograms recorded in the temperature range of 4.2 - 300 K it was found that all five sites A, B, C, D and E are populated by both kinds of atoms. Sites A and D are predominantly occupied by Co atoms while sites B, C and E by Cr atoms. The unit cell parameters a and c, hence the unit cell volume, increase with x, the increase being characteristic of the lattice paramater and temperature. Both a and c show a non-linear increase with temperature.