Magnetic properties of Nd_2Fe_(14)B/α-Fe nanocomposite magnets with yttrium addition

The phase evolution and magnetic properties of Nd9？xYxFe72Ti2Zr2B15 （x = 0,0.5,1,and 2） melt-spun nanocomposite ribbons were studied.It is found that Y addition not only enhances the formability of amorphous phase in the alloy,but also stabilizes the amorphous phase during the annealing treatment.The appropriate content of Y addition effectively enhances the remanence （Jr） of the annealed sample.The residual amorphous intergranular phase in the annealed sample optimizes the squareness of the loop,resulting in an larger maximum energy product （BH）max.The best magnetic properties,Jr = 0.78 T,Hci （coercivity） = 923.4 kA/m,and （BH）max = 98.5 kJ/m3,were obtained from the Nd8YFe72Ti2Zr2B15 ribbon spun at Vs = 4 m/s and annealed at 700°C for 10 min,which is composed of Nd2Fe14B,α-Fe,and amorphous phase.

Effect of yttrium addition on flow behavior of Cu-Zr-Al bulk metallic glass in the supercooled liquid region

The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the uniaxial compression tests. The results showed that the high temperature deformation behaviors were highly sensitive to strain rate and temperature, and the flow stress decreased with the increase of temperature, as well as with the decrease of strain rate. Additionally, the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass displayed smaller flow stress under the same condition. The flow behavior changed from Newtonian to non-Newtonian with increase of the strain rate, as well as the decrease of temperature, which could be explained by the transition state theory. We found that（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass had better flow behavior than the Cu_（43）Zr_（48）Al_9 bulk metallic glass in the supercooled liquid region. In addition, the processing maps of the two bulk metallic glasses were constructed considering the power dissipation efficiency. The optimum domain for thermal workability of the bulk metallic glass was located using the processing map, where the power dissipation efficiency was larger than 0.8. It was shown that the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass, which had larger area of optimum domain, had excellent thermoplastic forming.

Application of rare-earth element Y in refining impure copper

The effects of rare-earth element Y in refining impure copper were investigated in this paper. The composition, microstructures, and corrosion resistance properties of impure copper before and after refinement with Y were investigated using direct-reading spectrometry, inductively coupled plasma atomic emission spectrometry, optical microscopy, scanning electron microscopy, and potentiodynamic polariza- tion measurements. The results show that the concentrations of impurities S, As, Sb, Bi, A1, Cd, and Se are remarkably decreased. Adding an appropriate amount of Y refines the microstructure and enhances the corrosion resistance properties of impure copper in HC1 solution via a purification effect. The formation enthalpies of compounds formed between Y and various impurity elements were calculated on the basis of Miedema＇s theory. The thermodynamic mechanisms of the refinement of impure copper by Y were also discussed.

Characterization of mechanical properties and microstructures of spark plasma sintered and cryo-rolled AA2024−Y composites

The relationship between the microstructure and mechanical properties of the spark plasma sintered AA2024 Y composites subjected to cryo-rolling was investigated. Yttrium addition enhances the mechanical properties of the composites by promoting grain refinement and precipitation. However, there is a clear trend of initial increase and later decrease in the properties. Also, it is observed that 0.3 wt.% of yttrium is the optimum amount of reinforcement content to obtain the highest mechanical properties. To further improve the tensile strength of the composites, cryo-rolling was performed on the composites under standard cryogenic conditions by several passes up to a reduction of 25%. The mechanical properties and the corresponding microstructures of composites after cryo-rolling were correlated. The SEM and TEM microstructures reveal that the samples exhibit dual size grains, i.e., nanograins are formed as sub-grains within the actual grain. Due to the grain size reduction and the increase in the dislocation density, the tensile properties are remarkably improved compared to those of the composites before cryo-rolling. The highest mechanical properties like hardness, YS and UTS are found to be 153 HV, 539 MPa and 572 MPa, respectively, with a reasonable ductility in the composite with 0.3 wt.% Y.

Properties of Fe-20Cr-4Al-Y Alloys

1. Introduction Light rare earth addition can remarkablyenhance the service life of Fe-Cr-Al alloyfor electrical heating element, but itscontent in the alloy must be controlledbelow the level of 0.1 wt-%. When thecontent exceeds that, the performance

Solid solubility extension and microstructure evolution of cast zirconium yttrium alloy

Yttrium addition can improve the oxidation resistance, mitigate hydrogen embrittlement and thus enhance the mechanical properties of the zirconium alloy. To study solid solubility extension of yttrium in zirconium alloy, the lattice parameters of ：t-Zr phase in Zr-Y alloy were accurately determined by X-ray diffraction （XRD）. Yttrium exhibits solid solubility extension in the cast zirconium alloy which forms a metastable supersaturated solid solution with solubility limit of around 3 wt%. The effect of yttrium and thermal treatment on the microstructure of the alloys was investigated by optical microscopy （OM） and scanning electron microscope （SEM）. The cast Zr-Y alloy shows a normal polycrys- talline structure with dispersed α-Y particles when Y content is lower than 4 wt%, while the alloy shows a eutectic structure with dendrites formation when the Y content is higher. Yttrium exhibits a strong grain refining effect on zirconium alloy and precipitates from the metastable supersaturated Zr matrix after annealing at 700 and 900 ℃.

Microstructural characteristics and second-phase particles in yttrium-bearing Fe-10Ni-7Mn martensitic steels

In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing Fe-10Ni-7Mn steels were characterized. The results of X-ray analysis as well as scanning electron microscopy coupled with energy dispersive X-ray spectroscopy indicated the formation of （Fe, Ni, Mn）17Y2 precipitates with hexagonal structure in a Fe-10Ni-7Mn-0.8Y （wt.%） alloy. Lattice parameters of these precipitates were calculated as follows：a=0.8485 nm and c=0.8274 nm. Formation of Y2O3 sub-micron particles was also confirmed in both yttrium bearing steels via electrolytic phase extraction method. The effect of these precipitates on the prior austenite grain size was investigated. The results revealed that these precipitates had an effective role in controlling the prior austenite grain size.

Non-isothermal Crystallization Kinetics and Isothermal Crystallization Kinetics in Supercooled Liquid Region of Cu–Zr–Al–Y Bulk Metallic Glass

The crystallization kinetics of Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 bulk metallic glasses in non-isothermal and isothermal conditions was studied by differential scanning calorimetry.In the non-isothermal and isothermal modes,the average activation energy of（Cu43Zra8Al9）98Y2 is larger than that of Cu43Zr48Al9,meaning the higher stability against crystallization of（Cu43Zr48Al9）98Y2.In addition,the average activation energies for Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 calculated using Arrhenius equation in isothermal mode are larger than the values calculated by Kissinger-Akahira-Sunose method in non-isothermal mode,indicating that the energy barrier is higher in isothermal mode.The Johnson-Mehl-Avrami model was used to analyze the crystallization kinetics in the non-isothermal and isothermal modes.The Avrami exponent n for Cu43Zr48Al9 is above 2.5,indicating that the crystallization is mainly determined by a diffusion-controlled three-dimensional growth with an increasing nucleation rate,while the Avrami exponent n for（Cu43Zr48Al9）98Y2 is in the range of 1.5-2.5 in the non-isothermal mode,implying that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with decreasing nucleation rate.Finally,the Avrami exponents n for Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 are different in the non-isothermal and isothermal conditions,which imply different nucleation and growth behaviors during the crystallization processes.