Fe-based Bulk Amorphous Alloys Research Articles

Effects of spark plasma sintering parameters on properties of Fe-based bulk amorphous alloys

Fe-based bulk amorphous alloys were prepared by spark plasma sintering (SPS) with different parameters. The thermal stability of Fe-based bulk amorphous alloys was characterized by differential scanning calorimetry (DSC) to determine the thermodynamic characteristic temperature, such as glass transition temperature (Tg) and crystallization temperature (Tx). X-ray diffraction (XRD), Archimedes drainage method, universal material testing machine, Electrochemical workstation and scanning electron microscope (SEM) were utilized to analyze the phase composition, relative density, compressive strength, corrosion performance, and fracture morphology and corrosion morphology of Fe based bulk amorphous alloys. This experiment show that Fe-based amorphous powder can be made into Fe-based bulk amorphous alloy with the size of φ12 × 9 mm by SPS technology. Meanwhile, the sample prepared with the parameters of sintering temperature of 560 ℃, sintering pressure of 550 MPa and the holding time of 1 min basically maintains the amorphous structure, and it has good compressive strength of 678 MPa, Microhardness of 1351.2 HV, density of 94.4 %, and perfect corrosion resistance.

The use of DSC curves and the Kronmüller theory to study the level of structural defects of Fe-based bulk amorphous alloys

The use of DSC curves and the Kronmüller theory to study the level of structural defects of Fe-based bulk amorphous alloys

The crystallization process in a new multicomponent Fe-based bulk amorphous alloy: A kinetic study approach

The crystallization process in a new multicomponent Fe-based bulk amorphous alloy: A kinetic study approach

Corrosion and Mechanical Properties of Novel Fe-Based Bulk Amorphous Alloys

Corrosion and Mechanical Properties of Novel Fe-Based Bulk Amorphous Alloys

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Enhancement of plasticity by cryogenic thermal cycling on Fe80P13C7 bulk amorphous alloy

The effect of cryogenic thermal cycling on the plasticity of Fe80P13C7 bulk amorphous alloy was investigated. The plastic strain increases from 1.7% of the as-cast samples to 5.4% of the cryogenic thermal cycling treated ones, while the yielding strength does not have an obvious deterioration. The enhancement of plasticity can be ascribed to the rejuvenation induced more disordered high-energy states in structure, which corresponds to a creation of excess free volume and therefore helps to the formation of multiple shear bands. This work provides an effective method for the modification of plasticity of Fe-based bulk amorphous alloys.

Based on internal friction theory: Investigating of Fe-based bulk amorphous alloys on mechanical properties with different Si content

In the current work, internal friction and mechanical properties of a Fe41Co7Cr15Mo14-xC15B6Y2Six (x = 0.5, 1, 1.5 and 2 at.%) bulk metallic glasses (BMGs) was investigated. Investigations demonstrated that the Si content could play an important effect on the mechanical properties of Fe-based bulk metallic glasses. The influence of Si on mechanical properties may be related to the structural heterogeneity in the metallic glasses. The quasi-point defects theory was used to describe the structural heterogeneity. Quasi-point defect concentration represents the degree of structural heterogeneity of amorphous alloys. The addition of Si reduces the quasi-point defect concentration in the amorphous samples, and the low quasi-point defect concentration increases the modulus, hardness and fracture strength of the samples. The quasi-point defect concentration of the sample with 1 at.% Si content is the lowest. Results shows that the mechanical properties of amorphous alloy can be improved by adding appropriate an amount of Si.

Mechanical properties of Fe-based bulk amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy rods

Bulk amorphous Fe-based alloy rods were prepared via copper mold casting. The mechanical properties of the samples with diameters of 3 mm and 5 mm were investigated using the Vickers hardness. Microhardness tests demonstrated that the hardness changed at different parts in cross-sections of the amorphous alloy rods. It was small on the edges, but increased around the center. The 3 mm diameter amorphous rod was less hard than the 5 mm diameter rod under the same load. This suggests that there are hardness gradients at different positions and sizes in the same materials. This study provides a theoretical basis for understanding the relationship between the cooling rate, structure, and micro-morphology of Fe-based amorphous alloys.

Phase Transformations in an Fe-Based Bulk Amorphous Alloy inside a Ball Mill

The possibility of using a ball mill to obtain an amorphous state in bulk amorphous Fe61.4Ni3.6Cr3.2Si2.4Nb7.8Mn3.6B18 alloy is studied. The presence of a metastable phase in the initial reagents allows the rate of amorphization to be notably accelerated with an almost full transformation to the amorphous state. Compared to a quench-hardened tape, however, the content of the amorphous state obtained via mechanical milling is distinguished by a reduced content of boron and therefore a lower temperature of crystallization.

Microstructure and High-Field Magnetic Properties of Fe-Based Bulk Amorphous Alloys

In this paper the results of the structural and magnetic properties for bulk amorphous alloys Fe65Co10Y5B20 and Fe63Co10Y7B20 were presented. For the structural investigation was performed by X-ray diffractometry and Mossbauer spectroscopy. It was found that investigated samples were amorphous in the as-cast state. The magnetisation was measured within magnetic fields ranging from 0 to 2T using a vibrating sample magnetometer (VSM). On the basis of the hysteresis loops, the saturation magnetization value and the coercive field were determined.The investigation of the �magnetisation in the area close to ferromagnetic saturation� showed that the magnetisation process in strong magnetic fields is connected with point defects and Holstein-Primakoff paraprocess. Analysis of the high-field magnetization curves has facilitated the calculation of the spin wave stiffness parameter.

Pressure controlled micro-viscous deformation assisted spark plasma sintering of Fe-based bulk amorphous alloy

In this paper, the theoretical framework of viscous flow deformation is presented as a model to investigate the inherent role of applied pressure in the densification of Fe-based amorphous alloy powder during spark plasma sintering. The proposed model revealed that the evolution of the structural geometry of the powder compact resulted in an amplification of the applied pressure to a larger contact pressure. The resulting pressure controlled compressive viscous flow deformation of the particles exhibited the contribution of increased applied pressure towards enhancement of densification and thus confirmed the validity of the present model for analyzing pressure-assisted sintering of amorphous alloy powder. The application of this theoretical model correctly predicted the trend of increasing final density of the compacts with pressure while further improvement on its accuracy can be attained upon establishment of the relative contribution of mass flow and deformation of powder particles towards their consolidation.

Thermal stability and crystallization process in a Fe-based bulk amorphous alloy: The kinetic analysis

In this work, the thermal stability and non-isothermal kinetic analysis of crystallization process in (Fe41Co7Cr15Mo14Y2C15)94B6 amorphous alloy were investigated. The research findings revealed that crystallization process was done in four stages whereby the crystalline phases including Fe23 (B, C)6, Fe3Mo3C, and Mo3Co3C were formed. In order to determine the activation energy of every crystallization stages, the isoconversional methods were used. The activation energies were calculated about 550, 620, 550, and 820kJ/mol for I, II, III, and IV crystallization stages, respectively. Also, values of the rate constant at the peak temperature of crystallization, Kp; Avrami exponent, n; and growth dimensional, m; were determined by means of Augis-Bennett and Gao-Wang methods. Furthermore, for a more accurate determination of kinetic parameters including n, and m, these kinetic parameters were obtained by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) and Matusita. The values of m were calculated equal to 2, 1, 2, and 3 for I, II, III, IV crystallization stages, respectively. Also, the obtained nucleation index, showed that the rate of nucleation in I, II, and III crystallization stages were zero. Therefore, it can be acceptable that a large number of nuclei related to these stages already exist in the specimen.

Effects of Metalloid Elements on the Mechanical Properties of Fe-Based Bulk Amorphous Alloys

Effects of Metalloid Elements on the Mechanical Properties of Fe-Based Bulk Amorphous Alloys

Fe계 벌크 비정질 합금을 이용한 레이저 용접층의 파손 거동

In this study, Fe-based bulk amorphous alloy powder manufactured using gas atomization fabrication was used for laser welding. the fracture behavior of welding layer were analyzed. Tensile test results show that the destruction occurred immediately after the elastic deformation, After plastic deformation of the substrate, the destruction occurred. The actual maximum tensile strength of the welding layer and the substrate are 959.9MPa and 220.4MPa. welding layer were each 485.5±21 and 197.4±21 to the substrate and the actual microhardness, The welding layer has very high hardness. The welding layer showed a very weak fine acicular structure. The base material was shown in the micro structure appear a coarse grain. SEM observations of the fracture after the tensile test. Fracture morphology of the base metal and the welding layer showed ductile fracture and brittle fracture,

Enhanced plasticity of a Fe-based bulk amorphous alloy by thin Ni coating

A thin Ni coating well adhering on a Fe81Mo1P7.5C5.5B2Si3 bulk amorphous alloy (BAA) has been successfully prepared by electroless plating. It has been found that the plastic strain of the BAA is significantly increased to 8% (28 times enhanced) by the thin Ni coating. It shows that the coating with nanograin could promote the nucleation of shear bands, constrain the propagation of them and change the flow serration into a self-organized critical state, which drastically increase the plasticity of the BAA.

Effect of Neodymium on the Glass-Forming Ability and Magnetic Properties of Fe-Based Bulk Amorphous Alloys

The glass forming ability and magnetic properties were investigated for adding neodymium to the Fe71-xNb4B25Ndx (x=0, 3, 5, 7,10) alloys prepared by copper suction casting. It was found that proper neodymium (x=5~10 at.%) could improve glass forming ability of Fe-Nb-B alloys effectively. Bulk amorphous Fe66Nd5B25Nb4 and Fe64Nd7B25Nb4 samples were obtained and presented high thermal stability and good soft magnetic properties. The value of activation energy of the first crystallization peak for the bulk amorphous alloy Fe64Nd7B25Nb4 is 683 kJ/mol.

Effects of Cr or Mo Compositions on Mechanical Behavior of Fe-Base Bulk Amorphous Alloy

For enhancing wear property of Fe-based bulk amorphous alloys as structural materials, We investigate effects of Cr or Mo compositions on wear and mechanical behaviors of FeCSiBPMo and FeCSiBPAlCr system bulk amorphous alloys which are suction-cast into a copper mold by arc melting in an argon atmosphere using a suction casting technique. X-ray diffraction, differential scanning calorimeter and Scanning electron microscopy were used to observe the microstructure and surface morphologies. Cr-Fe or Mo-Fe substitutions led to a dramatic increase in the glass transition temperature as well as the supercooled liquid region. After the wear test, the mass loss of both BAAs decreased remarkably at higher element. Nanoindentation results indicate that with an increase of the Cr or Mo compositions, the hardness and elastic modulus increased in both BAA samples. These results suggest that wear behaviors of the BAAs corresponded to change in hardness, which means that fracture morphologies of worn surface are strongly dependent on surface hardening with high Cr or Mo content.

Crystallization of Fe-Based Bulk Amorphous Alloys

Abstract The aim of this paper is to present the results of crystallization studies for the bulk amorphous (Fe0.61Co0.10Zr0.025Hf0.025 Ti0.02W0.02B0.20)98Y2, Fe61Co10TixY6B20, Fe61Co10Ti2Y7B20 alloys. The crystallization of the alloys was studied by differential scanning calorimetry (DSC). The amorphicity of the investigated alloys in the as-quenched state was testified using Mossbauer spectroscopy, X-ray diffractometry and transmission electron microscopy. Moreover, X-ray diffractometry was applied to structure investigations of partially crystallized samples. The crystallization process in the investigated alloys occurs in one or two stages. Two peaks in the DSC curves can be overlapped or well separated indicating the complex crystallization processes. From X-ray diffraction we have stated that in both types of devitrification the crystalline phase can be ascribed to the α-FeCo. In the first stage the crystalline grains seem to grow from the nuclei frozen in the samples during the rapid quenching, whereas in the second one both the growth of the existed grains and creation of new ones during annealing may occur.

Fe-based bulk amorphous alloys with iron contents as high as 82 at%

Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe81P8.5C5.5B2Si3 BAA with a diameter of 1mm and a saturation magnetization of 1.56T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe82Mo1P6.5C5.5B2Si3 BAA rod with a diameter of 1mm, a high saturation magnetization of 1.59T, a high yield stress of 3265MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82at% would be advantageous and promising for industrial applications.

수중환경에서 Fe계 벌크 비정질 합금의 트라이볼로지적 거동

The tribological behavior of an Fe-based bulk amorphous alloy while sliding against a AISI 304 disc is investigated using a unidirectional pin-on-disc type tribometer in dry and distilled water environments. The rod-shaped bulk pins are fabricated by suction casting. The crystallinities of the bulk amorphous alloys before and after the friction tests are determined by X-ray diffraction. The friction coefficient and specific wear rate of the amorphous pin in the water environment are found to be twice and thrice as much as in the dry environment at a low applied pressure, respectively. However, at a higher pressure, the friction coefficient and specific wear rate are 0.4 and 1.02 mg/(Nm/s), respectively, in the water environment. A microstructure analysis shows that the worn surface of the alloy is characterized by delamination from the smooth friction surface, and thus delamination is the main wear mechanism during the friction test in dry sliding environment. In contrast, brittle fracture morphologies are apparent on the friction surface formed in distilled water environment. For the sample tested at a lower sliding speed, the XPS data from the oxide layer are similar to those of the pure element with weak suboxide peaks. For higher sliding speeds, all the main sharp peaks representing the core level binding energies are shifted to the oxide region.