Magnetic, electrical and mechanical properties of Fe40Mn40Co10Cr10 high entropy alloy.

A prototypical, single-phase, and non-equiatomic high entropy alloy Fe40Mn40Co10Cr10 has been mechanically deformed at room and cryogenic temperatures. Plastic deformation was accommodated via crystallographic slip at room temperature while transformation induced plasticity (TRIP) has been observed in samples deformed at 77 K. The stress-induced martensitic transformation occurred from face-centered cubic (FCC) to hexagonal close-packed (HCP) structures. A detailed electron backscatter diffraction analysis was utilized to detect phase change and evaluate the evolution of the HCP phase volume fraction as a function of plastic strain. Physical properties of undeformed and deformed samples were measured to elucidate the effect of deformation-induced phase transitions on the magnetic and electrical properties of Fe40Mn40Co10Cr10 alloy. Relatively small magnetic moments along with non-saturating magnetic field dependencies suggest that the ground state in the considered material is ferrimagnetic ordering with coexisting antiferromagnetic phase. The temperature evolution of the coercive fields has been revealed for all samples. The magnitudes of the coercive fields place the considered system into the semi-hard magnetic alloys category. The temperature dependence of the zero-field cooled (ZFC) and field cooled (FC) magnetization was measured for all samples in the low field regime and the origin of irreversibility in ZFC/FC curves was discussed. Besides, the temperature dependence of the resistivity in all samples was measured and the possible conduction mechanisms were discussed.

An experimental methodology to relate local strain to microstructural texture.

This paper introduces an experimental methodology for obtaining high resolution full-field strain measurements in polycrystalline metals. The (sub)grain level resolution of these measurements was indispensable for relating measured strain fields to observed microstructure in the material. Microstructural information was obtained through electron backscatter diffraction and the optical technique of digital image correlation (DIC) was used to acquire full-field deformation measurements. By spatially overlaying both sets of results, the effects of different microstructural features such as orientation, grain boundary character, misorientation between grains, and twin boundaries on material response can be quantitatively studied. To obtain the necessary resolution for such measurements, the images used in DIC had to be captured at high magnifications. This necessity reduces the field of view and constrains the area of interest that can be monitored. To address this issue, results from adjacent measurement areas are combined together to create a data set with high spatial strain resolution over a larger region than can otherwise be observed. The procedure for performing this technique is outlined here, along with benefits, drawbacks, possible modifications, and example applications of the technique to cyclic plasticity and fatigue crack growth.