“…Indeed, to the author’s knowledge, 3d transition metal based high entropy alloys exhibit very small magnetoresistance with a couple of exception like the AlCrFeCoNiCu system 15 , 49 . Moreover, there are number of reports showing significant magnetoresistance in rare earth elements based on high entropy alloys 45 , 50 . Figure 8 ( a ) Temperature dependence of the zero field resistivity of all samples.…”
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.
“…Indeed, to the author’s knowledge, 3d transition metal based high entropy alloys exhibit very small magnetoresistance with a couple of exception like the AlCrFeCoNiCu system 15 , 49 . Moreover, there are number of reports showing significant magnetoresistance in rare earth elements based on high entropy alloys 45 , 50 . Figure 8 ( a ) Temperature dependence of the zero field resistivity of all samples.…”
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.
“…At a field strength of more than 12 kOe, only one magnetic transition from paramagnetic to ferromagnetic state occurs in Gd-Tb-Dy-Ho-Lu HEA. Magnetic measurements of the MEA at different magnetic field reveal identical behavior for M(T) dependencies in comparison with those taken on similar systems [11,12,14,[16][17][18][19]. The ScGdHo alloy demonstrates a paramagnetic to antiferromagnetic transition at around 109 K when the magnetic field is less than 12 kOe and reveals a paramagnetic to ferromagnetic phase transformation in a field above 12 kOe.…”
Section: Magnetic and Magnetocaloric Propertiesmentioning
confidence: 64%
“…In the range of 70 -40 K, the magnetization is practically independent of T. And when the temperature drops below 25 K, we see a sharp growth in the magnetic response. Identical low-temperature anomalies are observed in similar rare-earth alloys in small magnetic fields [12,18]. Depending on alloy composition and magnetic field, speromagnetic, asperomagnetic, or spin-glass magnetic states can be formed in these systems.…”
Section: Magnetic and Magnetocaloric Propertiesmentioning
confidence: 92%
“…In this context, rareearth concentrated multi-principal-element systems or so-called high-entropy alloys (HEA) open up great perspectives in the search for efficient magnetic refrigerants. Recent studies of rare-earth HEAs have revealed complex magnetism and interesting caloric effects in these materials [11][12][13][14][15][16][17][18][19]. All these multicomponent alloys demonstrate strong magnetocaloric effect (MCE) over a wide temperature span (a table-like behavior) and consequently increased relative cooling power (RCP).…”
The search for effective solid-state refrigerant for magnetocaloric application is one of the main-stream topics in materials science. Rareearth multi-principal element alloys seem to be promising candidates for these purposes. In this study, we address the issues of structure formation, magnetic and magnetocaloric properties in ScGdHo medium entropy alloy. We perform the ab initio molecular dynamics simulations for the liquid and solid phases in this system and reveal a strong tendency to form a single-phase solid solu-tion. The experimentally fabricated alloy demonstrates a single-phase HCP crystalline structure with high density of defects. The magnetic measurements reveal a complicated magnetic behaviour in the material. The alloy exhibits antiferromagnetic or ferromagnetic behavior depending on the magnetic field. We have found that AFM order is preferable under a weak magnetic field and FM order occurs when the field strength exceeds 12 kOe. The alloy reveals a rather large coercive force in a wide temperature range up to the Neel point. The values of the magnetic entropy change and relative cooling power calculated for a magnetic field change of 0-5 T are 8.93 Jkg−1K−1 and 938 J/kg, respectively. The examined ScGdHo alloy demonstrates the best magnetocaloric properties among similar rareearth metal materials discovered to date.
“…Numerous parameters were proposed by various authors in order to predict whether an alloy will exhibit a microstructure consisting of a solid solution with no intermetallic phases [1,[7][8][9][10]. The matrixes of high entropy alloys are typically bcc or fcc, but recently even HEAs with the hcp matrix have been reported [1,[11][12][13][14]. The HEAs with the bcc matrix usually exhibit high strength and lower plasticity whereas fcc HEAs have lower strength and high plasticity [1,6].…”
High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.
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