Rare Earth Addition Research Articles

Effect of Nano Nd2O3 on the Microstructure and High-Temperature Resistance of G@Ni Laser Alloying Coatings on Ti-6Al-4V Alloy

Titanium and its alloys are widely used in high-end manufacturing fields. However, their low high-temperature oxidation resistance has limited their further application. Recently, laser alloying processing has attracted researchers to improve the surface properties of Ti, for which Ni coated graphite system is an excellent prospect due to its outstanding properties and metallurgical bonding between coating and substrate. In this paper, nanoscaled rare earth oxide Nd2O3 addition was added to Ni coated graphite laser alloying materials to research its influence on the microstructure and high-temperature oxidation resistance of the coating. The results proved that nano-Nd2O3 has an outstanding effect on refining coating microstructures, thus the high-temperature oxidation resistance was improved. Furthermore, with the addition of 1. 5 wt.% nano-Nd2O3, more NiO formed in the oxide film, which effectively strengthened the protective effect of the film. After 100 h of 800 °C oxidation, the oxidation weight gain per unit area of the normal coating was 14.571 mg/cm2, while that of the coating with nano-Nd2O3 addition was 6.244 mg/cm2, further proving that the addition of nano-Nd2O3 substantially improved the high-temperature oxidation properties of the coating.

Optical Properties of Cerium Oxide Doped Zinc Borotellurite Glass

The addition of rare earth, zinc, and borate in tellurite glass was found can enhance the glass properties and overcome its existing weaknesses. These include improving the glass forming ability and stability. In this study, cerium-doped zinc borotellurite glasses were produced using conventional melt-quenching technique and the optical properties of the glasses were investigated. UV-VIS spectra show that the absorption edge shifted to a higher wavelength with CeO2 addition from 0 until 0.05 mol. Consequently, the direct and indirect optical band gap was found to decrease from 3.60 to 2.07 eV and 3.28 to 1.46 eV respectively. On the contrary, the refractive index was found to increase from 2.326 to 3.017. This is attributed to the presence of cerium ions and the formation of non-bridging oxygens. Besides that, the Urbach energy found to be maximum at 0.02 mol CeO2 and minimum at 0.00 mol CeO2. This indicates that there are some structural disorders occur in the glass network as CeO2 introduced into the system. The molar refraction, molar polarizability, oxide ion polarizability and optical basicity exhibited similar trend of data as the CeO2 content was increased which signifies the relation of these parameters. Meanwhile, the metallization criterion is reported to be decreased, indicating that the glass sample become more metallized with the addition of cerium oxide.

Synergistic Effect of RE (La, Er, Y, Ce) and Al-5Ti-B on the Microstructure and Mechanical Properties of 6111Aluminum Alloy

For aluminum alloys, grain refinement is one of the effective methods for improving both strength and ductility. However, the refining effect of Al-Ti-B master alloy refiners deteriorates due to the agglomeration and sinking of the second phase particles. In this paper, the effects of rare earth type, rare earth content, and holding time on the microstructure and properties of Al-5Ti-B + RE/6111 were investigated by orthogonal experiment. It was shown that the addition of rare earth promoted the transformation of the β-Al5FeSi phase to anα-Al15(Mn,Fe)3Si2 phase, while the segregation of rare earth made it difficult for TiB2 to aggregate and inhibited the growth of TiAl3, resulting in more particles becoming effective nucleation substrates. The Al-5Ti-B + Ce master alloy developed based on orthogonal experiment improved the refinement recession problem well and improved the comprehensive mechanical properties of 6111 aluminum alloy. It was found that the addition of Al-5Ti-B + 0.1Ce, which had an ultimate tensile strength of 240.4 ± 2.2 MPa, successfully reduced the grain size by 73.8% and improved elongation by 37.8% compared to the base alloy. There search is of great significance for the preparation and application of high-performance rare earth 6111 aluminum alloy.

Influence of the Addition of Rare Earth Elements on the Energy Storage and Optical Properties of Bi0.5Na0.5TiO3–0.06BaTiO3 Polycrystalline Thin Films

Rare earth element-doped Bi0.5Na0.5TiO3-BaTiO3 (BNT-BT-RE) polycrystalline thin films were processed on a platinized substrate by chemical solution deposition. The microstructure, dielectric, and ferroelectric properties were investigated for all prepared films. It was found that the incorporation of rare earth elements into the BNT-BT matrix increases both the dielectric constant and the breakdown strength while maintaining low dielectric losses, leading to an enhancement of the energy storage density to Wrec = 12 and 16 J/cm3 under an effective field of E = 2500 kV/cm, for Nd- and Dy-based films, respectively. The optical properties of films containing the lanthanide element were investigated and the obtained results bear interest for luminescence applications. The simultaneous appearance of ferroelectric and optical properties in the system under investigation is very promising for advanced optoelectronic devices.

Effect of Y content on the hydrogen storage properties of ball-milled Mg2.4-xYxNi (x = 0.05, 0.1, 0.15, 0.2) alloys

Metal hydride hydrogen storage is currently the fastest growing and most promising method of hydrogen storage. In this paper, the Mg2.4-xYxNi (x = 0.05, 0.1, 0.15, 0.2) alloys were first melted by vacuum high-frequency induction melting furnace. Subsequently the alloy ingots were mechanically crushed and mechanically ball milled for the same time. And the microstructure and gaseous hydrogen storage properties of the ball-milled alloy were characterized thoroughly by varying the content of rare earth element Y. The results showed that the main phase of the alloy is the Mg2Ni phase, followed by the Ni3Y phase and a small amount of the Mg phase and MgNi2 phase. And the diffraction peaks of the Ni3Y phase are obviously enhanced with the increase of Y content, demonstrating that the exchange of Y for Mg promotes the formation of the Ni3Y phase, but the intermetallic compound Ni3Y phase was consistently present as a chemically inert material regardless of hydrogen absorption/desorption. Based on the hydrogen storage properties, the hydrogen storage alloys with different Y contents can be fully activated after one hydrogen absorption/desorption cycle, and the gestation period of the alloys with different Y contents showed a trend of decreasing and then increasing. For alloys with different Y contents, the Mg2.3Y0.1Ni alloy demands the shortest time for the initial activation of hydrogen absorption. And when the temperature is 573 K, the time taken to absorb 90% of the hydrogen capacity was 8 min, 6 min, 8 min and 12 min, and the time taken to release 90% of the hydrogen capacity was 4.6 min, 3.4 min, 5 min and 6 min for alloys with different Y contents, respectively. And the maximum values of hydrogen absorption/desorption saturation rate of Mg2.3Y0.1Ni alloy have reached 80.17% and 96.02%, respectively. The activation energy of hydrogen release of the alloys decreases from 123.9 kJ/mol to 113.1 kJ/mol. In contrast to the kinetic properties, there is no significant difference in the enthalpy and entropy changes for different Y contents, indicating that the addition of rare earth element Y has minimal effect on the thermodynamic properties of the alloy.

Enhanced thermal shock resistance of zirconia ceramics with multi-component rare earth and tourmaline addition

To broaden the application of zirconia ceramics in high-temperature environments, continuous attempts to improve their thermal shock resistance remain the focal point. In this work, 1–4 wt% tourmaline-doped 10 mol% CeO2-3 mol% Y2O3-1 mol% Yb2O3 costabilized zirconia ceramic(10Ce3Y1Yb) was prepared. The phase composition, microstructure, and thermal shock resistance of composite ceramics were investigated by XRD, Raman spectroscopy, SEM, TEM and water-quenching experiments. The results indicate that composite ceramics exhibit excellent thermal stability of the tetragonal phase, which is attributed to rare earth stabilizer doping. Mullite whiskers formed by tourmaline transformation could enhance the resistance of crack propagation and reduce the coefficient of thermal expansion of composite ceramics, thus improving the thermal shock resistance of composite ceramics. Both the results of the water-quenched experiments and calculations of the thermal stress crack stability parameter (Rst) indicated an improved thermal shock resistance of tourmaline-doped 10Ce3Y1Yb ceramics, with an increase in the residual strength retention ratio from 20.36% for 3 mol% Y2O3-stabilized zirconia (3YSZ) to 41.56% for 3 wt% tourmaline-doped 10Ce3Y1Yb ceramics.

Effects of rare earth elements addition on mechanical properties and corrosion behavior of GCr15 bearing steel under different heat treatment conditions

In this work, effects of rare earth addition on mechanical properties and corrosion behavior of GCr15 bearing steel under hot rolled, annealed, and quenched-tempered conditions were investigated via mechanical tests, electrochemical measurements, and immersion tests. Results show that rare earth elements can refine grains, improve hardness, tensile strength, and impact absorption energy of GCr15 bearing steel under different heat treatment conditions. Besides, it has been found that rare earth elements are beneficial to corrosion resistance of GCr15 bearing steel in 0.1 mol/L NaCl solution by electrochemical and immersion measurements.

Effect of cold-rolling deformation and rare earth yttrium on microstructure and texture of oriented silicon steel

Abstract In order to study the effect of cold-rolling deformation and rare earth Y on the microstructure and texture of 3.0% Si-oriented silicon steel, the microstructure and texture of cold-rolled oriented silicon steel with 60, 72, and 86% deformation are analyzed using electron backscatter diffraction and image analysis software. The experimental results show that the deformation band becomes narrower and the distribution of shear bands becomes denser with increasing cold-rolling deformation. Compared to the Y-free steel, cold-rolled sheet containing rare earth Y has greater shear bands. The pinning effect of rare earth Y hinders the dislocation movement, which leads to the increase of kernel average misorientation value and shear bands. With the increase of cold-rolling deformation, the texture concentrates on α and λ. This is mainly due to the change from {100} 〈001〉 to {001} 〈110〉, intensifying λ texture, and the change from {111} 〈112〉 to {111} 〈110〉, thus strengthening the α texture. The texture strength of cold-rolled sheets can be decreased by rare earth Y. But the γ texture strength in cold-rolled sheets containing Y is significantly higher than in those without Y. The γ texture strength can reach up to 7.3, and the strong points are mainly {111} 〈112〉. This is because the number of inclusions in steel increases with the addition of rare earth Y. In the process of grain nucleation, the {111} oriented grains nucleate heterogeneously on the inclusions. It forms a large number of {111} oriented grains and improves the γ texture strength.

Effect of rare earth on morphology and dispersion of TiB2 phase in Al-Ti-B alloy refiner

To investigate the effect of rare earth on size and distribution of TiB2 phase in aluminum alloy refiner, Al-5Ti-1B-RE master alloy was fabricated, and its microstructure and phase constitutions were investigated by the combination of first principles calculations and experimental investigation. The calculated results reveal that Ce has the most effective modification ability due to the most positive adsorption energy and the largest charge transfer value compared with other rare earth elements. Results of experimental investigation indicate that the addition of rare earth in the Al-5Ti-1B alloys can greatly refine the particle size of TiB2, improve the distribution of particles and lead to better refinement effect than that of the Al-5Ti-1B alloys without rare earth. Moreover, Ce has the best optimization effect, which agrees well with the calculated results.

Microstructure and Salt Fog Corrosion of Wrought Mg-Al-Zn and Mg-RE Alloys.

Wrought magnesium alloys have received attention due to their potential application as lightweight materials. However, their use is limited by their poor corrosion resistance. Rare earth additions have the potential to enhance corrosion resistance. The present work included a microstructural investigation and corrosion testing of the alloy WE-43, containing Nd and Y, which was compared against the more conventional compositions of AZ31 and AZ61 alloys. All three alloys exhibited a recrystallized equiaxed structure after hot rolling with the presence of second phases-precipitates. The WE-43 alloy exhibited a better corrosion resistance than AZ31 and AZ61 under salt fog testing, indicated by the lower depth of attack and lower weight loss. The second phases in the microstructure of AZ31 and AZ61 alloys determined their corrosion resistance. The second phases in the AZ31 and AZ61 alloys (based on Al-Mg and Al-Mn phases) were nobler than the Mg matrix and catholically acted, thus sacrificing the Mg matrix. The superior corrosion resistance of WE43 was due to the incorporation of Y in the oxide/hydroxide film. In addition, the second phases in the WE43 consisted of Nd and Y and were less noble than the Mg-matrix. Thus, they acted as anodic sites protecting the Mg-matrix. The above results show the beneficial effect of rare earth additions to wrought Mg alloys towards increased corrosion resistance.

Microstructure Evolution and Localized Corrosion Susceptibility of an Al-Zn-Mg-Cu-Zr 7xxx Alloy with Minor Cr Addition.

Microstructure optimization of Al-Zn-Mg-Cu-Zr aluminum alloys, particularly through recrystallization inhibition, for improved strength and corrosion resistance properties has been an important consideration in alloy development for aerospace applications. Addition of rare earth elements, sometimes combined with Cr, has been found to be beneficial in this regard. In this study, the role of a single addition of 0.1 wt.% Cr on microstructure evolution of an Al-Zn-Mg-Cu-Zr (7449) alloy during processing was systematically investigated by optical light microscopy, scanning electron microscopy, electron backscatter diffraction and scanning transmission electron microscopy. Susceptibility to localized corrosion after aging to T4, T6 and T76 conditions was evaluated by potentiodynamic polarization (PDP) measurements and an intergranular corrosion (IGC) test. A decrease in recrystallized fraction with 0.1 wt.% Cr addition was observed, which is attributed to the formation of Cu- and Zn-containing E (Al18Mg3Cr2) dispersoids and the larger as-cast grain size. Moreover, the depletion of alloying elements from solid solution due to the formation of the Cu- and Zn-containing E (Al18Mg3Cr2) dispersoids and η Mg(Zn,Cu,Al)2 phase at its interface affects grain-boundary precipitation. The observed decrease in localized corrosion susceptibility with minor Cr addition is correlated with the microstructure and equally discussed.

Local Corrosion Behaviors in the Coarse-Grained Heat-Affected Zone in a Newly Developed Zr-Ti-Al-RE Deoxidized High-Strength Low-Alloy Steel.

Oxide metallurgy technology can improve the microstructure of a coarse-grained heat-affected zone (CGHAZ) but introduces extra inclusions. Local corrosion behavior of the CGHAZ of a Zr-Ti-Al-RE deoxidized steel was investigated in this work using theoretical calculations and experimental verification. The modified inclusions have a (Zr-Mg-Al-Ca-RE)Ox core claded by a CaS and TiN shell. CaS dissolves first, followed by the oxide core, leaving TiN parts. This confirms that the addition of rare earth can reduce lattice distortion and prevent a galvanic couple between the inclusions and the matrix, while the chemical dissolution of CaS causes localized acidification, resulting in the pitting corrosion initiation.

Effect of Rare Earth Ce on Inclusions in Q345 Steel

Q345 steel is an important raw material for the production of suspension spring steel and valve spring steel. Improving its comprehensive mechanical properties and fatigue resistance and ensuring the production continuity of Q345 steel is a topic of general concern in the industry. The addition of rare earth can effectively control the number, size, morphology, composition and distribution of inclusions in Q345 steel, which is of great significance for improving the quality of Q345 steel. However, at present, the addition process of rare earth Ce in the production process of 55SiCr spring steel is faced with problems such as low yield and difficult continuous production of Shuikou nodules and blockage. However, adding rare earth slag to refining slag is an effective solution to improve the yield of rare earth Ce. However, there is still a lack of research in this direction in the industry. In order to improve the yield of rare earth Ce, determine the ratio of rare earth refining slag and achieve the best metallurgical effect, it is the main research direction of this project.

Assessment of the effect of small additions of some rare earth elements on the structure and mechanical properties of castings from hypereutectic chromium white irons

<abstract> <p>Article considers the influence of additions of rare earth elements such as Sm, La, Ce, Nd, and Y on the structure and properties of hypereutectic high-chromium white cast iron of grade G-X300CrMo27-2. To obtain an increased content of carbides in the studied cast iron samples, the carbon content was 3.75–3.9 and 4.1–4.2 wt%. The amount of rare earth elements additives added to the melt is 0.2% by weight. Data were obtained on the effect of overheating and cooling rate in the crystallization interval on the effect of rare earth additives, the structure and properties of white cast iron castings are given. According to the results of the microprobe analysis, it was shown that, under the chosen crystallization conditions, Sm, La, and Ce can form solid solutions with primary and eutectic carbides (FeCr)<sub>7</sub>C<sub>3</sub>. La and Ce form solid solutions with austenite. Nd and Y do not dissolve in iron chromium phases. All listed rare earth elements form phosphides and oxyphosphides. Experimental data are presented on the effect of rare earth elements on the size of primary (FeCr)<sub>7</sub>C<sub>3</sub> carbides and a hypothesis is proposed on the effect of rare earth elements on the crystallization process of hypereutectic chromium white cast irons. Experimental data are presented on the effect of REE additives on the microhardness of phases, hardness, strength, and resistance to abrasive wear of cast iron castings. It was found that the introduction of these additives into hypereutectic chromium white cast iron does not contribute to the modification of the structure and leads to an increase in the size of primary crystals, as well as a decrease in their mechanical properties. However, the addition of Y increases the abrasive wear resistance, but reduces the strength of castings made from such white cast iron.</p> </abstract>

Effect of rare earth addition on corrosion sensitivity of GCr15 bearing steel in marine environment

Recent study demonstrates that only under very low-oxygen conditions can rare earth (RE) play a vital role in improving the performance of RE steels. In this work, the effect of RE addition on marine corrosion of the low-oxygen GCr15 bearing steel has been investigated with the involved mechanisms having been explored. The results indicate that the low-oxygen GCr15 bearing steel exhibits rather low sensitivity to marine corrosion, and the substantially decreased number and size in the inclusions modified by RE addition are responsible for the remarkable performance of the steel. Besides, RE addition has no obvious impact on the structure of GCr15 bearing steel, and the corrosion pits initiate and proceed following the galvanic corrosion mechanism.

Effect of rare earth Y on microstructure and texture of oriented silicon steel during hot rolling and cold rolling processes

Abstract The effect of rare earth Y on precipitates and textures of the grain-oriented silicon steels, the composition, morphology, size, quantity of inclusions and texture evolution of hot-rolled and cold-rolled oriented silicon steel containing rare earth Y were studied using transmission electron microscopy, field emission scanning electron microscope, and electron backscatter diffraction. The results show that there are mainly spherical or ellipsoidal Y2O2S precipitates in the Y bearing silicon steel. Rare earth treatment effectively improves the precipitates’ morphology and restrains the precipitation of the long-strip MnS in the hot-rolled plate. Meanwhile, the microstructure is more uniform, and the recrystallized grains on the surface and the fiber structure in the central layer are larger after hot rolling compared with Y-free steel. Furthermore, with the addition of rare earth Y, the unfavorable brass texture and rotational cube texture in the hot-rolled plate are reduced. Meanwhile, the number of shear bands is increased and the strength of the favorable {111} 〈112〉 texture is improved in the cold-rolled plate, which helps develop the Goss texture during the annealing process.

Effect of rare earth elements on microstructure and mechanical properties of bainite/martensite bearing steel

This study aims to investigate the effect of rare earth (RE) elements on the microstructure and mechanical properties of bainite/martensite (B/M) bearing steel. For this purpose, GCr15 bearing steels with different RE contents were prepared and analyzed after experiencing B/M heat treatment. The results show that RE addition significantly delays the bainite transformation by reducing grain boundary energy and carbon diffusion rate, leading to a reduction of bainite volume fraction from 27.3% for bearing steel without RE addition to less than 14.5% for RE-treated steels, and the corresponding increase of martensite volume fraction from 39.1% to more than 50.2%. The volume fraction of retained austenite (RA) remains nearly unchanged. Meanwhile, the width of the bainite needles gets refined in RE-treated steels while martensite and RA blocks become bigger. Compared with bearing steel without RE addition, larger RA blocks in RE-treated steels unexpectedly have higher stability due to higher dislocation density and surrounding phases strength. Accompanied by the change of microstructure, the hardness in RE-Treated steels improves slightly, while the fracture toughness dramatically deteriorates which can be directly explained by two mechanical phenomena during toughness test. The one is that the RA in RE-treated steels is harder to transform into martensite and thus consumes less energy; The other one gives that cracks tend to propagate along grain boundaries or martensite interfaces with less energy consumption easily in RE-treated steels instead of breaking off bainite.

Effect of La/Nd ratio on precipitation kinetics and tensile properties of squeeze-cast Mg-Al-Zn-La-Nd alloys

The current study investigated the effect of adding La and Nd on the precipitation kinetics and tensile properties of AZ91 magnesium alloy. Mg-Al-Zn-La-Nd alloys with different W La /W Nd ratios were developed by squeeze casting. Typical characterization was conducted using optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy to analyze the effect of W La /W Nd on the aging behavior of Mg-Al-Zn-La-Nd alloys. Thermal analysis, Vickers hardness and tensile properties were measured using the differential scanning calorimetry, optical hardness tester and universal testing machine. The results show that the addition of RE increases the diffusion resistance of Al atoms in the matrix and increases the time interval to peak aging. The precipitation activation energy and tensile properties of Mg-Al-Zn-La-Nd alloys increase with the increase of W La /W Nd . The optimal tensile properties are obtained in the alloy with a W La /W Nd of 3/2. The co-addition of La and Nd increases the precipitation activation energy and atom diffusion resistance of the AZ91 alloy. The precipitation behavior of AZ91 alloy with the addition of rare earth elements is slower than that of AZ91 alloy.

Thermal stability, grain growth kinetics, mechanical properties, and bio-corrosion resistance of pure Mg, ZK30, and ZEK300 alloys: A comparative study

Thermal stability, grain growth kinetics, tensile properties, and corrosion resistance of commercially pure (CP) magnesium can be tailored by zinc addition in conjunction with small additions of zirconium and rare earth (RE) elements, which need to be systematically investigated. Accordingly, the thermal stability, grain growth kinetics, tensile properties, and bio-corrosion resistance of hot rolled CP Mg, and ZK30 (Mg-3Zn-0.5Zr) and ZEK300 (Mg-3Zn-0.5RE-0.5Zr) alloys were compared in this work. The solute drag effect of Zn in the ZK30 alloy and the Zener pinning effect of CeZn 5 compound in the ZEK300 alloy were responsible for the improved thermal stability and higher grain growth activation energy of these alloys compared to CP Mg. The tensile properties of hot rolled ZK30 and ZEK300 alloys were superior due to their fine grain sizes. Moreover, corrosion tests in simulated body fluid (SBF) solution confirmed the higher corrosion resistance of the ZEK300 alloy for biomedical implant applications. The shear punch testing (SPT) results revealed that the ZEK300 alloy can better retain its superior mechanical properties during deformation/testing at elevated temperatures. Grain growth annealing led to a decrement in strength but an increment in the total elongations, and hence, the highest tensile toughness was obtained for the ZEK300 alloy with an average grain size of ~ 8.5 μm. Accordingly, this work proposed that RE addition at the micro-alloying level to a lean Mg-Zn alloy is quite effective in the enhancement of thermal stability, room/elevated-temperature mechanical properties, and bio-corrosion resistance.

Mechanistic origin of the enhanced strength and ductility in Mg-rare earth alloys

Magnesium (Mg) alloys with low concentrations of rare earth additions are known to exhibit strengths and ductility that are significantly higher than those obtained in traditional Mg alloys. However, the mechanisms that underlie these improvements are still open to debate. We assessed these mechanism(s) by carrying out in-depth analysis of the deformation behavior in single crystals of pure Mg and a homogenized Mg-0.75 at.% Gd alloy oriented for twinning, pyramidal- and basal-slip. We observed a fivefold increase in basal CRSS, an eightfold increase in twinning CRSS and a fourfold decrease of the pyramidal/basal CRSS (P/B) ratio due to Gd addition. We also observed that while twinning and pyramidal slip activities were similar in the two material systems, basal slip was radically different. Specifically, basal slip was planar in the alloy but wavy in pure Mg. Our work reveals that these observations are a consequence of Gd-rich short-range ordered (SRO) clusters in the alloy. We show that interactions between dislocations and the SRO clusters would lead to significant increases in strength and 〈c+a〉 slip activity, and consequently, ductility improvements in homogenized polycrystalline Mg-Gd alloys.