Surface modification of （Tb,Dy）Fe_2 alloy by nitrogen ion implantation

Effects of nitriding modification on surface phase structure, morphology, corrosion resistance and magnetostriction of (Tb,Dy)Fe2 alloy were investigated by nitrogen ion implantation. Results showed that the surface REFe2 phase gradually decomposed and transformed into REN, α-Fe and Fe8N phases with the increase of nitrogen ion implantation dose. The surface morphology of the alloy had an obvious change after nitrogen ion implantation. The corrosion resistance properties of the alloy in acidic, alkaline and chloridion environment were also greatly improved. In addition, the magnetostriction performance of the alloy was almost not affected by ion implantation as the nitrided layer was quite thin and the operating temperature was very low. The results proved that nitrogen ion implantation was an effective method for surface modification of (Tb,Dy)Fe2 alloy.     

Research on microstructure and magnetostriction of Fe83Ga17Dyx alloys

The crystal structure, microstructure and the magnetostriction of Fe₈₃Ga₁₇Dy_x (x=0, 0.2, 0.4, 0.6) series alloys were studied. The results showed that the influence of the Dy on the crystal structure of the alloy was very small but the effect on the microstructure was significant when different contents of Dy were added into the Fe₈₃Ga₁₇ alloy, respectively. Meanwhile, the magnetostriction of Fe₈₃Ga₁₇Dy_{0. 2} alloy was greatly enhanced, the magnetostriction λ value reached 300×10^?6 at 400 (kA/m) magnetic field.     

Effect of Ho-doping on microstructure and magnetostriction of TbDyFe alloys

Tb0.3Dy0.7HoxFe1.95 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50, 0.65) quaternary alloys were prepared by arc-melting and followed by annealing. The phases present and structure of the alloys were determined using a D8-Advance X-ray diffractometer. The magnetostriction of the alloys was studied by standard strain gauge technique. The dependence of Ho content on the structure, magnetostriction and density of the alloys was investigated in detail. The research results showed that Ho-doping did not change MgCu2-type cubic Laves structure in Tb0.3Dy0.7Fe1.95. When Ho content x≤0.2, rich rare earth phase presented in the alloys increased and magnetostriction of the alloys reduced evidently with increasing x, but for alloys with x>0.2, the content of rich rare earth phase started to reduce and the magnetostriction increased quickly, especially at low magnetic field in the alloy with x=0.65 due to separation of rich rare earth phases on the surface of the alloy.     

X-ray diffraction analysis by Rietveld refinement of FeAl alloys doped with terbium and its correlation with magnetostriction

Fe₈₁Al₁₉ polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal direction.Microstructural examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 phase.As a consequence of doping with Tb,the lattice ...     

Surface modification of （Tb0.3Dy0.7）Fe1.95 alloy by ion nitriding process

Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of (Tb0.3Dy0.7)Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag-netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of (Tb0.3Dy0.7)Fe1.95 alloy.     

Magnetostriction and hysteresis of <110> oriented TbDyHoFe_1.95 alloy

(Tb0.36Dy0.64)1-xHoxFe1.95 magnetostrictive alloys with <110> orientation were prepared by zone melting directionally solidified method.The magnetostrictive performance and hysteresis of <110> aligned polycrystalline(Tb0.36Dy0 64)1-xHoxFe1.95 were investigated under applied magnetic field H(0相似文献   

Electron Microscopic Study on the Suction Cast In Situ Ti-Fe-Sn Ultrafine Composites

The current investigation reports detailed study on the microstructural evolution in the suction cast hypereutectic Ti₇₁Fe_29?x Sn _x alloys during Sn addition with x = 0, 2, 2.5, 3, 3.85, 4.5, 6, and 10 at. pct and the solidification of these ternary alloys using SEM and TEM. These alloys have been prepared by melting high-purity elements using vacuum arc melting furnace under high-purity argon atmosphere. This was followed by suction casting these alloys in the water-cooled split Cu molds of diameters, ? = 1 and 3 mm, under argon atmosphere. The results indicate the formation of binary eutectic between bcc solid solution ??-Ti and B2 FeTi in all alloys. ??-Ti undergoes eutectoid transformation, ??-Ti ?? ??-Ti + FeTi, during subsequent solid-state cooling, leading to formation of hcp ??-Ti and FeTi. For alloys x < 2, the primary FeTi forms from the liquid before the formation of eutectic with minute scale Ti₃Sn phase. For alloys with 2 ?? x ?? 10, the liquid is found to undergo ternary quasi-peritectic reaction with primary Ti₃Sn, L+Ti₃Sn ?? ??-Ti+FeTi, leading to formation of another kind of FeTi. In all the other alloy compositions (3.85 ?? x ?? 10), Ti₃Sn and FeTi dendrites are observed in the suction cast alloys with profuse amount of Ti₃Sn being formed for alloys with x ?? 4.5. The current study conclusively proves that the liquid undergoes ternary quasi-peritectic reaction involving four phases, L + Ti₃Sn ?? ??-Ti + FeTi, which lies at the invariant point Ti_69.2±0.8Fe_27.4±0.7Sn_3.4±0.2 (denoted by P). Below P, there is one univariant reaction, i.e., L ?? ??-Ti + FeTi for all alloy compositions, whereas above P, liquid undergoes one of the univariant reactions, i.e., L + ??-Ti ?? Ti₃Sn (Sn = 2, 2.5, 3, and 4.5 at. pct) or L + FeTi ?? Ti₃Sn for alloys (Sn = 6, 10 at. pct). For alloy with Sn = 3.85 at. pct, the ternary quasi-peritectic reaction is co-operated by two monovariant eutectic reactions, i.e., L ?? ??-Ti + FeTi below P and L ?? FeTi + Ti₃Sn above P. Detailed microstructural information allows us to construct liquidus projection of the investigated alloys. The results are critically discussed in the light of available literature data.     

Magnetostriction, composition and microstructure of Tb0.29（Dy1–xPrx）0.71Fe1.97 alloys with heat treatment

Tb_0.29(Dy_1-xPr_x)_0.71Fe_1.97 (x=0, 0.1, 0.2 and 0.3) alloys prepared by the directional solidification method were treated at 1073, 1123, 1173, 1223 and 1273 K for 4 h for homogenization, respectively. The magnetostriction, micro-morphology and composition distribution were studied by the standard resistance strain gauge technique, optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results indicated that heat treatment could make the microstructure of alloys homogeneous effectively and improve the magnetostriction significantly. The optimum temperature was 1223 K. Compared to the as-cast ones, the increase amplitudes of magnetostriction of the corresponding samples were 39.5%, 64.9%, 95.3% and 50.8% when x=0, 0.1, 0.2 and 0.3, respectively at the compressive stress of 2 MPa and a magnetic field of 80 kA/m. The compressive stress could also improve the magnetostriction. However, further Pr element addition and over high heat treatment temperature would lead to the excessive decomposition of PrFe₂ and destroy the homogeneity, resulting in the decline of magnetostriction of alloys.     

Microstructural Evolution of the Interface Between Pure Titanium and Low Melting Point Zr-Ti-Ni(Cu) Filler Metals

Low melting point Zr-based filler metals with melting point depressants (MPDs) such as Cu and Ni elements are used for titanium brazing. However, the phase transition of the filler metals in the titanium joint needs to be explained, since the main element of Zr in the filler metals differs from that of the parent titanium alloys. In addition, since the MPDs easily form brittle intermetallics, that deteriorate joint properties, the phase evolution they cause needs to be studied. Zr-based filler metals having Cu content from 0 to 12 at. pct and Ni content from 12 to 24 at. pct with a melting temperature range of 1062 K to 1082 K (789 °C to 809 °C) were wetting-tested on a titanium plate to investigate the phase transformation and evolution at the interface between the titanium plate and the filler metals. In the interface, the alloys system with Zr, Zr₂Ni, and (Ti,Zr)₂Ni phases was easily changed to a Ti-based alloy system with Ti, Ti₂Ni, and (Ti,Zr)₂Ni phases, by the local melting of parent titanium. The dissolution depths of the parent metal were increased with increasing Ni content in the filler metals because Ni has a faster diffusion rate than Cu. Instead, slow diffusion of Cu into titanium substrate leads to the accumulation of Cu at the molten zone of the interface, which could form undesirable Ti _x Cu _y intermetallics. This study confirmed that Zr-based filler metals are compatible with the parent titanium metal with the minimum content of MPDs.     

Microstructure and Hardness Properties Investigation of Ti and Nb Added FeNiAlCuCrTi x Nb y High Entropy Alloys

Properties of pure metals can be enhanced by alloying with other metallic or non-metallic elements according to the need. However, as multiple alloying elements in an alloy may lead to the formation of many intermetallic compounds with complex microstructures and poor mechanical properties, new types of metallic alloys called high entropy alloys with at least five elements with equimolar ratios were developed. In this study, FeNiAlCuCrTi _x Nb _y (x, y = 0, 0.5, 1.0, 1.5) alloys have been prepared using Ar arc melting technique. Microstructural studies using scanning electron microscope and XRD showed that Ti addition promoted secondary BCC₂ phase whereas, Nb acted as FCC stabilizer. Samples with combined Nb and Ti addition showed FCC₁ and FCC₂ structure with Nb-rich FCC₂ dendritic phase as dominant phase. Though, individual Nb and Ti additions have resulted in increased hardness, combined additions have resulted in highest hardness of 797 HV under 1 kg load.     

Magnetostriction Increase of Polycrystalline Fe-Al-B Thin Sheets after Thermomechanical Process

Magnetostrictive materials are applied in several types of sensors, actuators, and energy harvesting. In particular, for AC devices, thin materials are desired to reduce eddy current losses. It is well known that the magnetostriction of single crystals and textured materials is higher than in polycrystalline ones, however, the cost and manufacture speed are crucial to be used as parts of commercial devices. Therefore, polycrystalline samples are strong candidates for common applications. In this work, (Fe _x Al_100?x )_98.4B_1.6 (x = 86.6, 82 and 79.4) alloys were rolled down to 0.7 mm of thickness and annealed at 1473 K (1200 °C) for 2 hours aiming to reduce the thickness of the samples without deteriorating the magnetic properties. The alloys, even with higher contents of Al, were easily deformed to the thickness of 0.7 mm and this ability is attributed to the presence of the Fe₂B phase. After the thermomechanical process, new isotropic recrystallized grains emerged and the longitudinal magnetostriction increased to 75.8, 16.9, and 3.2 pct, achieving 28.3, 28.4, and 28.8 ppm, respectively, for x = 86.6, 82, and 79.4. The piezomagnetic coefficient obtained of 4 nm/A is a suitable actuating sensitivity.     

Nanoparticle-Induced Superior Hot Tearing Resistance of A206 Alloy

Al-Cu alloys (such as A206) offer high strength and high fracture toughness at both room and elevated temperatures. However, their widespread applications are limited because of their high susceptibility to hot tearing. This article presents a nanotechnology approach to enhance hot-tearing resistance for A206. Specifically, γ-Al₂O₃ nanoparticles were used, and their effects on the hot-tearing resistance of the as-cast Al-4.5Cu alloy (A206) were investigated. While it is well known that grain refinement can improve the hot-tearing resistance of cast Al alloys, the current study demonstrated that nanoparticles can be much more effective in the case of A206. The hot-tearing susceptibilities (HTSs) of A206 alloy and its Al₂O₃ nanocomposite were evaluated by constrained rod casting (CRC) with a steel mold. Monolithic A206 and M206 (the Ti-free version of A206) alloys with the B contents of 20, 40, and 300 ppm from an Al-5Ti-1B master alloy addition were also cast under the same conditions for comparison. The results showed that with an addition of 1 wt pct γ-Al₂O₃ nanoparticles, the extent of hot tearing in A206 alloys was markedly reduced to nearly that of A356, an Al-Si alloy highly resistant to hot tearing. As compared with grain-refined A206 or M206, the hot-tearing resistance of the nanocomposites was significantly better, even though the grain size was not reduced as much. Microstructural analysis suggested that γ-Al₂O₃ nanoparticles modified the solidification microstructure of the eutectic of θ-Al₂Cu and α-Al, as well as refined primary grains, resulting in the enhancement of the hot-tearing resistance of A206 to a level similar to that of A356 alloy.     

( Tb,Dy) Fe2合金表面离子注入渗氮改性及抗腐蚀性能研究

采用离子注入技术在(Tb,Dy)Fe2稀土超磁致伸缩材料表面引入氮离子进行改性处理,研究了加速电压对材料表面相结构、微观形貌、表面硬度、抗酸碱腐蚀性能及磁致伸缩性能的影响.结果表明:离子注入渗氮后,(Tb,Dy)Fe2合金表面的REFb相分解,生成了REN,α-Fe和Fe8N新相,材料表面微观形貌发生了明显变化,表面硬度明显提高.通过测试极化曲线研究了渗氮前后(Tb,Dy)Fe2合金在不同PH值NaCl溶液中的抗酸碱腐蚀性能,发现pH值相同条件下渗氮处理后(Tb,Dy) Fe2合金的自腐蚀电位Ecorr较渗氮前明显正移且有钝化现象发生.在加速电压140 kV,离子注入剂量5.0×1017 ion.cm -2条件下渗氮处理的(Tb,Dy)F合金,处于20℃,3.5％ NaCl溶液环境中,pH=4时,△Ecorr=0.23413 V; pH =7时,△Ecorr =0.18992 V; pH=10时,△Ecorr =0.01268 V,渗氮处理后(Tb,Dy)Fe2合金的抗酸腐蚀性能明显增强,抗碱腐蚀性能变化不明显.随着pH值的增大,渗氮与未渗氮(Tb,Dy) Fe2合金的抗腐蚀性能均变差.由于离子注入表面渗氮的渗氮层很薄,渗氮温度很低,渗氮处理没有破坏材料的内部基体结构,因此渗氮后材料渗氮处理没有破坏材料的内部基体结构,其磁致伸缩性能几乎未受影响.研究表明离子注入渗氮是(Tb,Dy)Fe2磁致伸缩材料表面改性的一种有效方法.     

Effect of Nb Concentration on Thermal Stability and Glass-Forming Ability of Soft Magnetic (Fe,Co)-Gd-Nb-B Glassy Alloys

Addition of a small amount of Nb to the (Fe,Co)-Gd-B glassy alloy in (Fe_0.9Co_0.1)_71.5−x Nb _x Gd_3.5B₂₅ increased the stabilization of supercooled liquid. The largest supercooled liquid region of 104 K was obtained for the x = 2 alloy. A distinct two-stage-like glass transition was observed with further incresing Nb content. The nanoscale (Fe,Co)₂₃B₆ phase precipitated in the glassy matrix after annealing, while the two-stage-like glass transition disappeared, indicating that the anomalous glass transition behavior originates from the exothermic reaction for the formation of the (Fe,Co)₂₃B₆ phase in the supercooled liquid region. The glass-forming ability (GFA) also increased by addition of Nb, leading to formation of the bulk glass form for the Nb-doped alloys. The best GFA with a diameter of over 3 mm was achieved for the x = 4 alloy. The (Fe,Co)-Gd-Nb-B glassy alloys exhibited good magnetic properties, i.e., rather high saturation magnetization of 0.81 to 1.22 T, low coercive force of 2.5 to 5.8 A/m, and low saturated magnetostriction of 9 to 19 × 10⁻⁶. In addition, the glassy alloys also possessed very high compressive fracture strength of 3842 to 3916 MPa and high Vickers hardness of 1025 to 1076.     

Effect of Partial Substitution of Mn for Ni on Mechanical Properties of Friction Stir Processed Hypoeutectic Al-Ni Alloys

In this study, the mechanical properties of as-cast and FSPed Al-2Ni-xMn alloys (x?=?1, 2, and 4 wt pct) were investigated and compared with those of the as-cast and FSPed Al-4Ni alloy. According to the results, the substitution of 2 wt pct Mn for 2 wt pct Ni leads to the formation of fine Mn-rich intermetallics in the microstructure increasing the tensile strength, microhardness, fracture toughness, and specific strength of alloy by 22, 56, 45, and 35 pct, respectively. At higher Mn concentrations, the formation of large Mn-rich platelets in the microstructure reduces the tensile properties. Friction stir processing at 12 mm/min and 1600 rpm significantly enhances both the strength and ductility of the alloy. The tensile strength, yield strength, fracture strain, fracture toughness, microhardness, and specific strength of FSPed Al-2Ni-4Mn alloy improved by 97, 83, 30, 380, 152, and 110  pct, respectively, as compared to those of the as-cast Al-4Ni alloy. This can be attributed to dispersion strengthening of Ni- and Mn-rich dispersoids, formation of ultrafine grains, and elimination of casting defects. The fractography results also show that the brittle fracture mode of the as-cast Mn-rich alloys turns to a more ductile mode, comprising fine and equiaxed dimples in FSPed samples.     

The Effect of Dy Substitution on the Glass-Forming Ability and Crystallization Behavior of Mg65Cu10Ni10Y10Zn5 Metallic Glass

The glass-forming ability, thermal stability, and crystallization behavior of Mg₆₅Cu₁₀Ni₁₀Y_10-xZn₅Dy_x (x?=?0, 2, and 4) alloys were investigated. The partial substitution of Dy for Y increases the activation energy of the first crystallization, but it decreases the glass-forming ability and thermal stability. Analyses on crystallization kinetics suggest that the substitution of Dy for Y decreases the nucleation rate. In addition, the examination of the crystallization phase after the isothermal annealing indicated that Dy addition suppresses the formations of Mg₂Cu and Mg and that it promotes the formation of MgZn crystalline phase. The decreasing glass-forming ability with the Dy substitution can be attributed to the narrower supercooled liquid region, higher Gibbs free energy, and the change of crystallization products.     

Effect of microstructure on fracture characteristics of Ti-6Al-2Sn-2Zr-2Mo-2Cr-Si

The effects of intermetallic compounds of Ti₃Al (α ₂) and silicide separately on fracture characteristics of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-62222S) alloy were investigated in this study. The alloys with only Ti₃Al and only silicide precipitated were established by aging treatments at temperatures of 913 K followed by air cooling and 1088 K followed by water quenching, respectively. X-ray diffraction analysis results showed that the volume fraction of either Ti₃Al or silicide increases with increasing aging time. Tensile properties, namely, yield stress (0.2 pct proof stress), ultimate tensile strenght, and elongation of as-received alloy are much better than those of the aged alloys. The strength of the alloy with only Ti₃Al is better than that of the alloy with only silicide, while elongation of the alloy with only silicide is better than that of the alloy with only Ti₃Al. Fracture toughness, J _IC, of the alloy with only silicide is better than that of the alloy with only Ti₃Al. The intergranular fracture appears in the alloy with only Ti₃Al. Coarsening of Widmanstätten α structure and increasing ductility of β phase during aging are considered to be effective for increasing fracture toughness.     

Influence of Extrusion on the Microstructure and Mechanical Behavior of Mg-9Li-3Al-xSr Alloys

Mg-9Li-3Al-xSr (LA93-xSr, x = 0, 1.5, 2.5, and 3.5 wt pct) alloys were cast and extruded at 533 K (260 °C) with an extrusion ratio of 28. The microstructure and mechanical response are reported and discussed paying particular attention to the influence of extrusion and Sr content on phase composition, strength, and ductility. The results of the current study show that LA93-xSr alloys contain both α-Mg (hcp) and β-Li (bcc) matrix phases. Moreover, the addition of Sr refines the grain size in the as-cast alloys and leads to the formation of the intermetallic compound (Al₄Sr). Our results show significant grain refinement during extrusion and almost no influence of Sr content on the grain size of the extruded alloys. The microstructure evolution during extrusion is governed by continuous dynamic recrystallization (CDRX) in the α-Mg phase, whereas discontinuous dynamic recrystallization (DDRX) occurs in the β-Li phase. The mechanical behavior of the extruded LA93-xSr alloy is discussed in terms of grain refinement and dislocation strengthening. The tensile strength of the extruded alloys first increases and then decreases, whereas the elongation decreases monotonically with increasing Sr; in contrast, hardness increases for all Sr compositions studied herein. Specifically, when Sr content is 2.5 wt pct, the extruded Mg-9Li-3Al-2.5Sr (LAJ932) alloy exhibits a favorable combination of strength and ductility with an ultimate tensile strength of 235 MPa, yield strength of 221 MPa, and an elongation of 19.4 pct.     

Effect of Zr Addition on Microstructure and Properties of FeCrNiMnCoZr x and Al0.5FeCrNiMnCoZr x High Entropy Alloys

In this study, the effect of Zr addition on phase formation, microstructure, and hardness of FeCrNiMnCoZr _x and Al_0.5FeCrNiMnCoZr _x were investigated. High entropy alloys (HEA) were synthesized using arc melting technique in argon (Ar) atmosphere (x = 0, 0.1, 0.2, 0.3). Ingots were homogenized for 24 h at 900 °C in Ar atmosphere. Phase formation, microstructure and hardness of HEAs were investigated using field emission scanning electron microscope, X-ray diffraction and Vickers microhardness tester. Electron micrographs of HEAs showed majorly dendritic(DR) and interdendritic(ID) phases. For both FeCrNiMnCoZr _x and Al_0.5FeCrNiMnCoZr _x alloys, amount of ID phases is seen to increase with increased Zr content. Aluminium containing HEAs showed fine needle-shaped precipitates dispersed throughout the matrix phase. XRD results confirmed the presence of mixed FCC/BCC phases in FeCrNiMnCoZr _x alloys and BCC as majority phase in Al_0.5FeCrNiMnCoZr _x alloys. As the Zr content increased, hardness of HEA increased.     

Magnetostriction and hysteresis of <110> oriented TbDyHoFe1.95 alloy

(Tb_0.36Dy_0.64)_1-xHo_xFe_1.95 magnetostrictive alloys with >110< orientation were prepared by zone melting directionally solidified method. The magnetostrictive performance and hysteresis of >110< aligned polycrystalline (Tb_0.36Dy_{0 64})_1-xHo_xFe_1.95 were investigated under applied magnetic field H (0>H>4 kOe) in the temperature range from ?60 to 80 °C with 0, 5 and 10 MPa pre-stress. The (Tb_0.36Dy_0.64)_1-x Ho_xFe_1.95 alloys (x>0.3) have the character of giant magnetostriction from ?60 to 80 °C. An obvious magnetostrictive “jump” effect was observed in these samples from ?60 to 80 °C. The pre-stress and temperature dependence of the W_h was also examined. Between the temperature range from ?60 to 80 °C, the magnetostriction increased with temperature decreased, while the magnetostriction hysteresis decreased, with the pre-stress increased, but the magnetostriction and the magnetostrictive hysteresis increased.