Elastic modulus anomaly in a Fe-Mn-Cr-C cryogenic steel

With dynamic mechanical analysis, magnetism measurement and microstructure characterization, the elastic modulus anomaly in a Fe-Mn-Cr-C cryogenic steel was investigated to clarify the correlation of magnetic transition with lattice instability and microstructural evolution. It was found that the elastic modulus begins to decrease abnormally at temperatures higher than the critical temperature of the paramagnetic-antiferromagnetic transition and a noticeable drop of elastic modulus occurs around the Neel temperature upon cooling. These findings suggest that the elastic modulus anomaly is closely associated with lattice instability across a large temperature range and that the paramagnetic-antiferromagnetic transition worsens the lattice instability. Meticulous microstructure characterizations show that during the elastic modulus anomaly the nanodomains with the body-centered tetragonal structure emerge, providing the evidence for the lattice instability of the austenite in the Fe-Mn-Cr-C steel.