Spinodal Decomposition Structure Research Articles

Insight of the microstructure evolution and performance enhancement of spinodal decomposition in (Ti, Zr)C composite carbide ceramics: Multiscale simulation and experimental investigation

Traditional carbide ceramics face a sharp trade-off between hardness and toughness, leading to a significantly reduced lifespan under harsh service conditions like wear, impact, corrosion, and high temperatures. The spinodal decomposition leads to the formation of nano-lamellar structures, serving to refine grain sizes, thus paving the way to simultaneously improve the hardness and toughness of composite carbide ceramics. A wide range of composite carbides can be prepared, but their complex microstructure evolution during aging makes performance optimization extremely challenging. In this work, a strategy by combining the multiscale simulations and experiments is proposed to systematically study the influence of the composition and process on the spinodal decomposition structure and performance. Taking (Ti, Zr)C carbide ceramics as a representative example, three distinct compositions of (Ti, Zr)C solid solutions were successfully synthesized via a sol-gel combined with spark plasma sintering method at 1800°C, guided by thermodynamic calculations. The influence of aging temperature and duration on spinodal decomposition microstructure evolution in (Ti, Zr)C carbide ceramics was studied by integrating phase-field simulations and first-principles calculations with key experimental observations. After spinodal decomposition, numerous nanoscale nodular structures form, accompanied by the generation of dislocations, leading to a significant improvement in both hardness and toughness of the composite carbides. After aging at 1300°C for 3 h, the composite carbides achieved peak hardness at 2436 HV, accompanied by a fracture toughness of 3.24 MPa·m1/2. This research provides a scientific approach to improving the hardness and toughness of carbide ceramics through spinodal decomposition, offering essential theoretical foundations for microstructural control and synergistic optimization of performance in innovative carbide ceramics.

Solidification and tribological behaviors of CoCrFeNiSi0.5-(Al,Ti) non-equiatomic high entropy alloy coatings fabricated by direct laser deposition

In order to evaluate the difference in the effects of Al and Ti elements on the microstructure and tribological behaviors of CoCrFeNi-based high entropy alloy (HEA) coatings, CoCrFeNiSi0.5-(Al,Ti) non-equiatomic HEAs coatings were prepared using direct laser deposition (DLD). The phase constitution, solidification microstructure and tribological behaviors of the HEA coatings were investigated. The results indicated that CoCrFeNiSi0.5 HEA coating was composed of face centered cubic (FCC) phase with microstructure of columnar and cellular grains. The addition of Al and Ti led to a columnar-to-equiaxed transition (CET) in the HEA coatings. When only Al was added (CoCrFeNiSi0.5Al0.5), the primary phase transformed into a body centered cubic (BCC) phase (94 vol%). Additionally, Cr3Si formed in the interdendrite (ID) region, and a spinodal decomposition structure emerged in the dendrite (DR) region. Conversely, with the inclusion of Ti alone (CoCrFeNiSi0.5Ti0.5), the matrix maintained its FCC phase, but Ni16Ti6Si7 (G phase, 20.9 vol%) and Cr15Co9Si6 (15.1 vol%) were generated in the ID and DR regions, respectively. Incorporating both Al and Ti (CoCrFeNiSi0.5Al0.5Ti0.5) significantly reduced the G phase content in the ID region to 7.9 vol% and led to the formation of dispersed Fe3Al nanoparticles with an average size of 99 nm in the DR region. The CoCrFeNiSi0.5 HEA coating exhibited the lowest hardness (249 HV0.1), the highest friction coefficient (0.778), and the poorest wear resistance. For the HEA coatings containing Al and Ti, the microhardness significantly increased to over 700 HV0.1, and the friction coefficient decreased to around 0.6. However, the wear resistance of the CoCrFeNiSi0.5Al0.5 HEA coating was almost equivalent to that of the CoCrFeNiSi0.5 with a wear loss of 5.1 mg. By contrast, the HEA coatings containing Ti demonstrated notably improved wear resistance, with wear losses of only 2.2 mg and 2.4 mg for the CoCrFeNiSi0.5Ti0.5 and CoCrFeNiSi0.5Al0.5Ti0.5 HEA coatings, respectively.

Spinodal decomposition-mediated multi-architectured α precipitates making a metastable β-Ti alloy ultra-strong and ductile

The chemical boundaries inside the ultrafine spinodal decomposition structure in metastable β-Ti alloys can act as a new feature to architect heterogeneous microstructures. In this work, we combined two semi-empirical methods, i.e., the d-electron theory and the e/a electron concentration, to achieve the spinodal decomposition structure in a metastable β Ti-4.5Al-4.5Mo-7V-1.5Cr-1.5Zr (wt.%) alloy. Utilizing the spinodal decomposition structure, the aged Ti-Al-Mo-V-Cr-Zr alloys showed multi-architectured α precipitates spanning from micron-scale (primary αp) to nano-scale (secondary αs) that were uniformly distributed in the β-domains. Being compared with the forged sample, the multi-scale heterogeneous microstructure enables the aged β-Ti alloy to have ultra-high strength (yield strength ∼1366 MPa and ultimate tensile strength ∼1424 MPa) and an appreciable ductility (∼9.3 %). Strengthening models were proposed for the present alloys to estimate the contribution of various microstructural features to the measured yield strength. While the solid solution strengthening, β-spinodal strengthening, and back stress strengthening made comparable contributions to the strength of the forged alloy, the back stress strengthening was the predominant strengthening effect in the aged alloy. This alloy design approach based on chemical boundary engineering to construct multi-architectured α precipitates provided an effective strategy for achieving an outstanding combination of ultra-high strength and ductility in metastable β-Ti alloys.

Microstructure and magnetic properties of Dy-added Alnico alloys

Alnico permanent alloys are still irreplaceable and show great potential in high temperature applications considering their excellent thermal stability, while the market for Alnico alloys is limited by their low coercivity. Rare-earth addition has been shown to increase the coercivity of Alnico alloys. In this work, the effects of Dy-addition on the crystal structure, microstructure, spinodal decomposition phases and magnetic characteristics of Alnico alloys were systematically investigated. The results indicate that the Dy element forms Dy-rich precipitates and influences the morphology and composition of spinodal decomposition structure. The 0.3 wt% Dy addition improves the coercivity from 132 kA·m−1 for the Dy-free alloys to 141 kA·m−1 for the Dy-added alloys and slightly optimizes the thermal stability. The enhancement of coercivity is attributed to the refined and uniform spinodal decomposition structure by reducing the mismatch degree and coherency strain. However, the magnetic properties of the 0.6 wt% Dy added alloy decrease due to the damaged structure with excessive Dy-rich phases and more connected α1 phases. A method for improving coercivity and thermal stability is suggested.

Cooperative regulation of mechanical properties and magnetoresistance effect in high-entropy alloys by spinodal decomposition

Adjusting the phase composition of high-entropy alloys is an effective approach to change its mechanical and magnetic properties. In this study, FeCoNiCr high-entropy alloys with Al addition (AlxFeCoNiCr; x = 0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.75) were prepared by argon arc melting to obtain a special spinodal decomposition structure. There precipitated body-centered cubic (BCC) phase in the face-centered cubic (FCC) phase matrix for the samples with Al (x = 0.25, 0.5, 0.75) addition. Furthermore, the increase in the Al content (x = 1.0, 1.25, 1.75) transformed the alloy into a BCC phase, and resulted in a spinodal decomposition in the alloy. This spinodal decomposition created a low-misfit coherent nanostructure combining the enriching AlNiCo ordered B2 matrix with enriching Fe–Cr BCC disordered nanoprecipitates. The difference in the distribution of chemical elements of the two phases leads to different magnetic properties and induces the magnetoresistance (MR) effect. This provides a pathway for the design of advanced functional high-entropy alloys.

Enhanced hydrogen storage properties of Ti40-xV45Zr15Crx alloys by dual-phase nanostructures of eutectic and spinodal decomposition

Multi-principal elements alloys (MPEAs) with body center cubic (BCC) structure have shown great potential in hydrogen storage. However, the multi-cycle activation process and the high desorption temperature have inhibited their applications. In this study, the Ti40-xV45Zr15Crx (x = 1, 2, 3 at. %) alloys with three different BCC phases are synergized, and high hydrogenation capacities of over 2 wt% are achieved in the first hydrogen absorption. Owing to the formation of spinodal decomposition nanostructure in Ti38V45Zr15Cr2 alloy, 90 % of total hydrogen capacity is reached in 30s at 250 °C under 1 MPa H2, which indicates no incubation time is needed for activation. The Ti38V45Zr15Cr2 alloy also shows the highest reversible hydrogen storage capacity with fastest kinetics at 200 °C. The hydrogenation reaction is controlled by the 1D diffusion process of H atoms according to JMAK model. The spinodal decomposition structure can accelerate the decomposition of H2 molecules and the diffusion of H atoms by providing extra energy from large lattice distortion. The high-density interfaces in nano-eutectic structure can serve as active sites for the nucleation of hydrides and fast paths for the diffusion of H atoms.

Microstructure, Mechanical Property, and Wear Behavior of NiAl-Based High-Entropy Alloy

Based on the excellent comprehensive mechanical properties of high–entropy alloy (HEA), the NiAl-based HEA was designed to achieve excellent high-temperature strength, toughness, and wear resistance. In this work, vacuum arc melting technology was used to prepare (NiA1)78(CoCrFe)16.5Cu5.5 HEA, and its microstructure, phase composition, and mechanical properties were systematically studied. The results showed that (NiA1)78(CoCrFe)16.5Cu5.5 HEA was composed of FCC and BCC/B2, with a spinodal decomposition structure in the matrix, and nano-precipitation in the interdendritic, exhibiting a good high-temperature performance. At 600 °C, the compressive fracture strength is 842.5 MPa and the fracture strain is 24.5%. When the temperature reaches 800 °C, even if the strain reaches 50%, the alloy will not fracture, and the stress–strain curve shows typical work hardening and softening characteristics. The wear coefficient of the alloy first increases and then decreases with the increase in temperature in the range of room temperature to 400 °C. However, the specific wear rate shows the opposite trend. At 100 °C, the wear rate reaches the lowest of 7.05 × 10−5 mm3/Nm, and the wear mechanism is mainly abrasive wear.

Effects of Al and Co contents on the microstructure and properties of AlxCoCryFeNi high-entropy alloys

AlxCoCryFeNi high-entropy alloys (HEAs) were prepared by vacuum arc melting. The effects of Al and Cr contents on the microstructure, corrosion resistance and mechanical properties of the alloys were evaluated. Results showed that with an increase in Cr content, the phase of the alloys changed from FCC + B2 + BCC to FCC + B2 + BCC + FeCr when the Al content was 0.75 (X = 0.75). Coarse FCC dendrites decreased. The alloys exhibited two mixed BCC/B2 structures with different morphologies: (i) the granular B2 phase distributed in the BCC matrix and (ii) the maze-like spinodal decomposition structure. At X = 1.5, the FCC and FeCr disappeared, and the microstructure of the alloy transformed into a mixed structure with a nanoparticle-like BCC phase distributed in the B2 matrix. During compression testing, the fracture type was brittle fracture for all alloys, except for X0.75Y1, which exhibited excellent mechanical properties with a fracture strain of 40% due to partial plastic tearing. Both B2 and FeCr phases, which were rich in AlNi and Cr, respectively, showed reduced corrosion resistance. For the former, the loose structure of Al2O3 reduced the compactness of the passivated film; for the latter, the precipitation of the Cr-rich phase led to a Cr-poor region in the periphery. The Al0.75CoCrFeNi alloy exhibited the highest corrosion resistance, which was attributed to its reduced FeCr and B2 phases.

Effect of spinodal decomposition structure of alnico alloy on magnetic viscosity and magnetization reversal

The slow decay of permanent magnet magnetization with storage time will greatly affect the accuracy of precision instruments. The alnico is a traditional permanent magnetic material with excellent stability, and the research on its stability cannot be ignored. Magnetic field heat treatment is a key process that affects the microstructure of the alnico alloy. The alnico alloys with different α1 phase orientations and aspect ratios were prepared by adjusting the magnetic field intensity during spinodal decomposition. With the increase of magnetic field strength, the aspect ratio of the α1 phase increases significantly, and the orientation becomes better, which leads to the increase of coercive force and remanent magnetization, but the magnetic viscosity coefficient decreases. The demagnetization process of alnico samples was characterized by Lorentz transmission electron microscopy (LTEM) and electron holography. At the magnetic field interval of 200 Oe, the area of irreversible magnetization reversal of the S3 is significantly larger than that of the S0. The first-order reversal curves (FORC) show that most the randomly oriented α1 phases are reversible magnetization reversal, and the interaction field is smaller than that of neatly arranged α1 phases. This structure results in better stability. The alnico alloy without a magnetic field during spinodal decomposition sacrifices some magnetic properties but obtains better stability, which provides a research direction for stabilizing treatment by adjusting microstructure.

Achieving high strength and ductility in high-entropy alloys via spinodal decomposition-induced compositional heterogeneity

The compositional heterogeneity in high-entropy alloys (HEAs) has been reported to be an inherent entity, which significantly alters the mechanical properties of materials by tuning the variation of lattice resistance for dislocation motion. However, since the body-centered cubic (BCC) structure is not close-packed, the change of lattice resistance is less sensitive to the normal concentration wave compared to that in face-centered cubic (FCC) structured materials. In this work, we selected a refractory bcc HEAs TiZrNbTa for the matrix and added a small amount of Al to facilitate the special spinodal decomposition structure. In particular, (TiZrNbTa)98.5Al1.5 displayed a typical basket-weave fabric morphology of spinodal decomposition structure with a characteristic periodicity of ∼8 nm and had an optimal combination of strength and ductility (the yield strength of 1123 ± 9 MPa and ductility of ∼20.7% ± 0.6%). It was determined that by doing in situ TEM mechanical testing, the plastic deformation was dominated by the formation and operation of dislocation loops which provided both edge and screw components of dislocations. The synergetic effect of the remarkable chemical heterogeneity created by the spinodal decomposition and the spreading lattice distortion in high entropy alloys is quite effective in tuning the mobility of different types of dislocations and facilitates dislocation interactions, enabling the combination of high strength and ductility.

Controlling the Thermal Stability, Threshold Voltage, and Thermoelectric Properties of Cuprous Sulfide Thermoelectrics.

Cu-ion liquid-like copper sulfide materials have excellent thermoelectric properties, while their applications are limited by their high-temperature decomposition and electric field-driven Cu precipitation issues. In particular, high thermoelectric properties and electric field-driven degradation are difficult to reconcile because liquid-like Cu ions are dominant in low κ and high ZT, while they cause electric field-driven degradation. Here, we control the sintering current and duration time to remove the Cu1.8S phase, thereby inhibiting the thermal decomposition of the copper sulfide samples, and introduce the Fe element into the sample matrix to improve its resistance to electric field-driven degradation. We reveal that the kinetic process of Cu1.8S phase decomposition can be suppressed by increasing the relative density of the sample or covering a layer of dense coating/film on the surface of the sample. However, as long as the Cu1.8S phase is present in the sample, it cannot maintain thermal stability above 450 °C. Furthermore, we find that the Fe element forms a nanogrid spinodal decomposition structure in the sample matrix, which acts as a barrier wall to prevent the long-range diffusion of liquid-like Cu ions and inhibit the electric field-driven degradation. The freely movable liquid-like Cu ions in the grid maintain a strong scattering of phonons in a short range, so the sample possesses low κ and high ZT. Then, a strategy to unify the high thermal decomposition temperature, high threshold voltage, and high thermoelectric performance of copper sulfide thermoelectric materials is proposed: transforming the Cu1.8S phase and introducing a liquid-like Cu ion migration barrier.

Refinement strengthening, second phase strengthening and spinodal microstructure-induced strength-ductility trade-off in a high-entropy alloy

The strength-ductility trade-off of high-entropy alloy (HEA) is a major factor affecting its potential application. In this work, the mechanical properties and deformation mechanisms of as-cast and cold rolled-annealed (RA) Fe23Co24Ni24Cr21Al8 (at%) HEA samples were comparatively investigated. Compared with as-cast sample, the cold-rolled and annealed sample possessed higher yield strength (725 ± 12 MPa), ultimate strength (1042 ± 23 MPa) and sustained good ductility (46.7 ± 4.5%), suggesting excellent strength-ductility combination was achieved in RA sample. The as-cast and RA samples both possessed dual phases including FCC and BCC, but the volume fraction of BCC in as-cast sample was very few. The RA sample exhibited significantly decreased grain size and more volume fraction of BCC compared with as-cast sample, indicative of the refinement strengthening and second phase strengthening. Meanwhile, a high density of dislocation walls and spinodal decomposition structure were observed in RA sample, which contributed to the outstanding ductility.

Compositional interpretation of high elasticity Cu–Ni–Sn alloys using cluster-plus-glue-atom model

The D022 or L12-γ′ phase strengthened Cu–Ni–Sn alloys possesses a characteristic microstructure, exhibiting the distribution of precipitated phase with smaller size on a spinodal decomposition structure, which leads to that the composition of the precipitated phase and Cu matrix cannot be precisely measured and restriction of the accurate compositional design of the alloys. The present work initials to introduce the cluster-plus-glue-atom model for compositional interpretation of the industrial Cu–Ni–Sn alloys, and then optimizing the cluster formula according to the measured composition of the relevant precipitated phases. Moreover, the solid solution content of Ni or the precipitation content of Sn are calculated based on the optimized cluster formula, and establishing the relationship between the alloy composition and properties. It indicates that the strength mainly relays on the precipitation content of Sn while the conductivity depends on the solid solution content of Ni, which is also suitable for the Cu–Ni–Sn–Zn (Co) alloys or Cu–Ni–Al alloys with similar characteristics. Additionally, the ratio of strength/resistivity increases in the alloys as the increasing Sn content under the premise of close to 3 of Ni/Sn (or (Ni + Co)/Sn) atomic ratio, but the discontinuous precipitation is easily to generate. Therefore, the improved properties of the alloys cannot be attained via the reducing ratio of Ni/Sn (or (Ni + Co)/Sn) atomic ratio solely. Based on the above, this work provides theoretical support and application methods for the compositional design and performance prediction of coherent D022 or L12-γ′ phase strengthened alloys.

Microstructure evolution and mechanical properties of AlCrFe2Ni2(MoNb)x high entropy alloys

The AlCrFe2Ni2(MoNb)x multiphase high entropy alloys were designed, prepared and characterized. The synergistic effect of Mo and Nb alloying on microstructures and mechanical properties of AlCrFe2Ni2-based high entropy alloy were investigated. By synergistic alloying with Mo and Nb, the volume fraction of the BCC phase increased, and a novel Laves phase with hexagonal close-packed(HCP) structure was formed. With the increase of Mo and Nb content, the alloys dramatically transformed from equiaxed grain with multiple phases to dendrites with the spinodal decomposition structure of the A2 phase and B2 phase, as well as inter-dendrites with the eutectic structure of the FCC phase and Laves phase. Furthermore, the solidification behavior of the alloys varied considerably as the increase of Mo and Nb content. The coexisting solidification microstructure of the eutectic structure and spinodal decomposition structure in the AlCrFe2Ni2(MoNb)0.3, AlCrFe2Ni2(MoNb)0.5 and AlCrFe2Ni2(MoNb)0.7 alloys have hardly been observed in other HEAs. The increase of Mo and Nb elements tends to segregate in the front of the liquid–solid interface, which hinders the growth of the FCC phase and leads to the formation of fine rod-like morphology. The synergistic effect of the fine grain strengthening and the solid solution strengthening resulted in high yield strength and fracture strength of 878 MPa and 2830 MPa, maintaining high plastic strain of 43.7%. Further increasing the content of Mo and Nb would lead to the increase of brittle Laves phase, with the second phase strengthening becoming the dominant strengthening mechanism, resulting in an increase in yield strength to 1549 MPa and a decrease in plastic strain to 8.6%. The investigation results would provide a guide for strengthening the macroscopic mechanical properties of eutectic high entropy alloys through synergistic alloying effect.

Effects of porosity and pore microstructure on the mechanical behavior of nanoporous silver

The tensile strength of nanoporous silver (AgNPs) is investigated by experiments and molecular dynamic analysis. Effects of sintering temperature on the porosity and ultimate strength of AgNPs are studied. The tensile properties of AgNPs with different micro structures and porosities are determined. The phase field method is adopted to develop the spinodal decomposition open-cell porous microstructure. AgNPs with cube, gyroid, and sphere pores generally show brittle fracture in tension, while AgNPs with spinodal decomposition structure show brittle fracture at low porosity and ductile fracture at high porosity. The influences of porosity on the Young’s modulus and ultimate strength are studied. The predicted stress-strain curves are validated by the Gibson-Ashby model and experimental data. The microstructure is investigated by common neighbor analysis and dislocation extraction algorithm. It is found that the dislocation nucleation sites are concentrated near the pore surfaces, the evolution of strain-stress curve is related to the dislocation density. Molecular dynamics simulations reveal that the uniaxial tensile deformation is accompanied by accumulation of stacking faults in ligaments, as well as the formation of Lomer–Cottrell locks at the junctions of dislocation. The influences of porosity and pore surface to the dislocation nucleation and tensile strength are discussed.

Design and characterization of FeCrCoAlMn0.5Mo0.1 high-entropy alloy coating by ultrasonic assisted laser cladding

In this work, FeCrCoAlMn 0.5 Mo 0.1 high-entropy alloy (HEA) coating was successfully synthesized on 316L stainless steel by ultrasonic assisted laser cladding. The effect of dilution rate on the phase composition of FeCrCoAlMn 0.5 Mo 0.1 coatings was investigated by thermodynamic calculation, solidification simulation and microstructure characterization. The mechanical properties, tribological behavior and corrosion resistance of FeCrCoAlMn 0.5 Mo 0.1 coating prepared under optimal dilution rate were also characterized in detail. The results show that the increase of dilution rate results in the transition of single solid solution (BCC) into dual-phase solid solution (FCC and BCC) of FeCrCoAlMn 0.5 Mo 0.1 coating. The TEM analysis reveals that FeCrCoAlMn 0.5 Mo 0.1 coating with optimal dilution rate (∼27.3%) is virtually composed of disordered BCC phase and ordered BCC (B2) phase. The spinodal decomposition structure and numerous dislocations were found in the grains. The average microhardness of FeCrCoAlMn 0.5 Mo 0.1 coating is ∼624.1 HV, which is more than 2.6 times higher than that of the substrate. The wear resistance of FeCrCoAlMn 0.5 Mo 0.1 coating was found significantly improved almost 4 times than that of 316L stainless steel. The passive current density of FeCrCoAlMn 0.5 Mo 0.1 coating is reduced by an order of magnitude compared with that of 316L stainless steel, proving the better corrosion resistance of FeCrCoAlMn 0.5 Mo 0.1 coating. • A new FeCrCoAlMn 0.5 Mo 0.1 HEA coating without defects was successfully prepared by ultrasonic assisted laser cladding. • Excessive dilution will result in phase transition of FeCrCoAlMn 0.5 Mo 0.1 HEA coating. • The spinodal decomposition structure and numerous dislocations are found in the coating. • FeCrCoAlMn 0.5 Mo 0.1 HEA coating shows good wear resistance and corrosion resistance.

Phase Transition Mechanism and Mechanical Properties of AlCrFe2Ni2 High‐Entropy Alloys with Changes in the Applied Carbon Content

To understand the effect of carbon addition on dual‐phase high‐entropy alloys (HEAs), the mechanism of phase transition and mechanical properties of AlCrFe2Ni2Cx (x = 0, 0.06, 0.12, 0.18, 0.24) are investigated systematically. The results show that carbon addition induced the growth and aggregate of disordered noodle‐like face‐centered cubic (FCC) phases. The volume fraction of the FCC phase increases from 33.2% to 51.2% as the C content increases. The Al and Ni in the alloys are segregated at the phase boundaries. Disappearance of the spinodal decomposition structure compose of a disordered body‐centered cubic (BCC) structure and an ordered BCC structure (B2). The BCC phase transform into a spherical B2 phase with increasing C content. The experimental mechanical properties show that the yield strength of the HEAs is closely related to the volume fraction of BCC phase as the C content increases. The ε phase (Cr, C carbonization) precipitate in an FCC phase when the C content is above 2.0 at%. The hardness of the HEAs increases from 310 to 357 HV as the C content increases. The compressive strength and the fracture strain of the alloy decreases as the C content increases.

Determination of cooling rates by the structure of spinodal decomposition and impact melting in meteorite substance

Cooling rates of meteoritic iron–nickel alloys were estimated using a processing of morphological features of their structure. All data have been acquired with optical and scanning electron microsc...

Excellent magnetic properties determined by spinodal decomposition structure of Alnico alloy doped SmCo5-based ribbons

5 wt% Alnico5 doped Sm(Co0.9Cu0.1)5 ribbons were prepared by melt spinning at 40 m/s, and the effects of magnetic field heat treatment (MHT) and annealing on the phase composition, microstructure and magnetic properties of the ribbons were investigated. The results show that all three ribbons consist of Co-rich SmCo5-and Sm-rich CeCo5-type phases with a spinodal structure. Annealing increases the content of SmCo5-type phase, enlarges the component differences between the two types of Sm(Co,M)5 phases and accumulates Alnico alloying elements into 3 g site of CeCo5-type phase. MHT narrows the ingredient differences between them, prompting the Alnico alloying elements to diffuse simultaneously into 2c and 3 g sites of two Sm(Co,M)5 phases, and concentrates the CeCo5-type phase on grain boundaries of the SmCo5-type phase to pin the magnetic domain movement. The as-spun ribbons present the magnetic properties of Hc = 32.0 kOe, Mr = 46.2 emu/g and Ms = 59.1 emu/g, while MHT increases them by 10.0%, 10.2% and 19.5%, respectively. These results can contribute to disclose the multi-element doping mechanism for improving the magnetic properties of SmCo5-based or similar alloys.

Study on Microstructure and Properties of Cu-9Ni-6Sn Alloy Applied for Electric Measurement

High strength elastic alloy has an important role in the manufacture of electrical equipment and machine building. Along with the development of information and telecommunications technology, the application of this alloy in electrical and electronic equipment is very increasingly. Even on boards or connectors of common electrical equipment such as computers, cell phones, these connectors are usually made of high strength elastic copper alloy. The design required features are small, precision built, with high mechanical strength and elasticity, heat resistance, abrasion and corrosion resistance in the operating environment to ensure its/the power and signal stability for a long time. The design trend is reduced in size but still assure the equipment quality is growing significantly and the corporation to manufacture equipment is researched thoroughly. Accordingly, this article presents the research results about the alloy copper with 9%Ni and 6%Sn which has the high elastic strength and elasticity properties of elastomers after heat treatment. The properties of the microstructure, hardness, conductivity, dry friction coefficient, the corrosion resistance of the alloy from which to determine the parameters for the materials selection procedure and the design of the manufacturing of magnetic contact of this alloy. The results of the study show that after heat treatment and deformation, the Cu-9Ni-6Sn has a strength of alloy up to 1200MPa, the elastic limit is 1100MPa and the conductivity is 8.4%IACS, respectively. The values ​​of this characteristic are consistent with the working conditions of the electrical contact. With the deformation process combined with the heat treatment process, the results of our research group created a single-phase homogeneous microstructure that is chemically stable with the spinodal decomposition in appropriate to the treatment of aging process. By modern methods, this paper demonstrates the durability of the alloy due to the spinodal decomposition during aging treatment at 350°C. This structure of spinodal decomposition is about 20-40nm in size, dispersed throughout the entire cross-section of the sample.