Rare Earth Addition Research Articles

Effect of Addition of Rare Earth Elements on the Microstructure, Texture, and Mechanical Properties of Extruded ZK60 Alloy

Effect of Addition of Rare Earth Elements on the Microstructure, Texture, and Mechanical Properties of Extruded ZK60 Alloy

Effects of Ce and La on microstructure and sulfide stress cracking susceptibility of API-5CT-C110 casing steel

This study investigated the effects of Ce and La addition on microstructure and sulfide stress cracking (SSC) behavior of API-5CT-C110 casing steel. The role of rare earth (RE) elements on the SSC resistance was assessed via uniaxial tensile testing and double cantilever beam testing (NACE TM0177 A and D methods). The experimental results show that the appropriate addition of RE is beneficial to the improvement of SSC resistance without compromising strength. RE addition is found to refine prior austenite grains and carbides, and modify the coarse inclusions into spherical RE oxysulfides. The electron backscattered diffraction analysis indicates that the steel with RE has lower high angle grain boundary and kernel average misorientation, which could effectively hinder crack propagation and thus reduce the SSC susceptibility. Furthermore, the proportion of deformed grains is reduced significantly due to RE addition, and substructure grains with low storage energy are increased, which is also a vital factor enhancing the SSC resistance.

Wear and corrosion mechanisms of Ni–WC coatings modified with different Y2O3 by laser cladding on AISI 4145H steel

Abstract In order to evaluate the effect of rare earth Y2O3 on the wear and corrosion properties of WC–Ni composite coatings, X-ray diffraction, scanning electron microscopy(SEM), electrochemical polarization curve, electrochemical impedance spectroscopy (EIS), and friction and wear tests were used to analyze the metallographic structure, corrosion characteristics in simulated seawater and friction and wear principle of the composite coatings. Results of SEM revealed that the microstructure of the Y2O3 added coatings was refined with the grains changing smaller and the impurity disappearing. The EIS results proved that the addition of Y2O3 brought a positive influence on the corrosion resistance by reducing the capacitance and increasing the R f and R c. The hardness of the coatings with Y2O3 addition tends to be smooth without wild fluctuation, and the coating with 0.5 wt% Y2O3 owned the hardness values reaching 850 HV. With the addition of rare earth elements, the coefficient of fiction values decreased, reaching the lowest (0.3418) at the content of Y2O3 of 0.5 wt%. The surface of the coating without Y2O3 appears grooved due to the abrasive wear; the coatings with Y2O3 did not suffer serious wear and tear. The coating with 0.5 wt% Y2O3 exhibited the best corrosion resistance and wear resistance properties in all the specimens.

Rare earth effect on laser produced plasma dynamics during pulsed laser deposition of doped cobalt ferrite

The addition of rare earth elements the ferrites can lead to significant changes in structural, magnetic and electric properties of bulk materials and also of thin films deposited by pulsed laser deposition. The present study relies on the analysis of the laser induced plasma of three sets of cobalt ferrite targets doped with various concentrations of RE elements (Dy, Gd, Yb) and proposes a correlation of the derived results with structural investigations of the films obtained during the same experiment. ICCD imaging and space-and time-resolved optical emission spectroscopy techniques were used to obtain information on the dynamics and excitation temperatures of various species found in the laser produced plasmas (LPP). Initial investigations on the global behavior of the LPP revealed that the addition of RE reduced the drift velocities of the formed plasma structures, the lowest ones being observed for the targets doped with the heaviest RE (Yb). Space-and time-resolved spectroscopy measurements applied for all main elements (Fe, Co and RE - both neutral and ionic species) showed a complex dynamic system, with decreased/increased kinetic energies for neutrals/ions at high dopant concentrations, suggesting a possible re-sputtering effect at the films surface. The individual excitation temperatures of the main elements derived from Boltzmann plots increased as the RE content was augmented via radiative collision events due to their larger diameters compared with Co, Fe or O. The spatial distribution of electron temperature can be explained by the charge separation occurring with the addition of RE in the investigated systems.

Impact of Rare Earth Addition on Creep Rupture Behavior of 316LN Austenitic Stainless Steel at 700°C

Effect of rare earth (RE) on creep rupture behavior of 316LN austenitic stainless steel (316LN steel) was investigated after crept at 700°C under the stress in the range from 125MPa to 200MPa, by the optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show RE addition in 316LN steel increased the creep rupture ductility at high stress, but reduced the creep rupture ductility at low stress. Under 200MPa, RE addition increased the creep rupture strain of 316LN steel from 0.558 to 0.787 but the creep rupture strain after crept under 150MPa was decreased from 0.875 to 0.566. The fracture mode of 316LN steel was also apparently impacted by the RE addition. The typical ductile fracture feature of homogeneous dense dimples was obviously observed in NRE steel after crept rupture under all stresses. While in 32RE steel, small amount of intergranular fracture fractographs under low stress appeared instead of partial dimples under high stress. Moreover, it is noted that RE addition in 316LN steel promotes to precipitate a great number of fine Laves particles within grains. These Laves particles strengthening the matrix resulted in the strain concentration on grain boundaries, which might sensitively induce crack initiation on grain boundaries during long-term creep under the low stress.

Single-phase colour-tunable yellow light copper doped zinc sulfide quantum dots for fabrication of white LEDs

To achieve large-scale commercialized use of white quantum dots light-emitting diodes (WQLEDs). It is vital to find environmentally friendly and inexpensive luminescent materials without rare earth participation. In this paper, the zinc sulfide quantum dots with different Cu2+ contents (ZnS:Cu-QDs) were prepared by one-step hydrothermal method, the quantum yield can reach 27.65 % and the thermal decomposition temperature is 610 ℃. Furthermore, the luminescence mechanism of ZnS:Cu-QDs was explored. The wavelength-tunable WQLEDs were fabricated. The WQLEDs exhibit from standard white light to warm white light with a relative colour temperature in the range of 4764–3851 K. The as-prepared WQLEDs from ZnS:Cu0.8 %-QDs show a warm white light with International Commission on Illumination (CIE) coordinates of (0.4009, 0.4265), colour rendering index (CRI) of 72.1, and the correlated colour temperature (CCT) of 3851 K at an input voltage of 3.4 V. This research provides a promising way for achieving WQLEDs by single phase quantum dots without the addition of rare-earth elements.

Low-oxygen rare earth steels.

Rare earth (RE) addition to steels to produce RE steels has been widely applied when aiming to improve steel properties. However, RE steels have exhibited extremely variable mechanical performances, which has become a bottleneck in the past few decades for their production, utilization and related study. Here in this work, we discovered that the property variation of RE steels stems from the presence of oxygen-based inclusions. We proposed a dual low-oxygen technology, and keeping low levels of oxygen content in steel melts and particularly in the raw RE materials, which have long been ignored, to achieve impressively stable and favourable RE effects. The fatigue life is greatly improved by only parts-per-million-level RE addition, with a 40-fold improvement for the tension-compression fatigue life and a 40% enhancement of the rolling contact fatigue life. We find that RE appears to act by lowering the carbon diffusion rate and by retarding ferrite nucleation at the austenite grain boundaries. Our study reveals that only under very low-oxygen conditions can RE perform a vital role in purifying, modifying and micro-alloying steels, to improve the performance of RE steels.

Preparation and dynamic behavior of W-Mo-Y co infiltrated layer on the surface of 45 steel parts

In this paper, W-Mo-Y co infiltration were carried out on the surface of 45 steel wedge components by plasma solid-state surface metallurgy technology. The phase, hardness, friction and wear properties before and after W-Mo co infiltration and W-Mo-Y co infiltration were systematically studied. The diffusion kinetics such as diffusion coefficient and diffusion activation energy were calculated by Fick's second diffusion law, and the effect of Y on the diffusion of W and Mo atoms in the infiltrated layer was obtained. It is found that the addition of rare earth Y element increases the diffusion coefficient of W and Mo atoms and reduces the diffusion activation energy, which has a certain catalytic effect. And the W-Mo-Y co infiltration significantly improves the surface hardness and wears resistance of the parts and prolongs the service life of the parts.

Deposition mechanisms and characteristics of nano-modified multimodal Cr3C2–NiCr coatings sprayed by HVOF

Abstract Nano-modified multimodal and conventional Cr3C2–NiCr coatings were fabricated by high-velocity oxygen-fuel spraying deposited on CuCrZr substrates. Results showed that individual nano-modified multimodal Cr3C2–NiCr particles were composed of nano (25−180 nm), submicron (200 nm to 0.5 μm), and micron (2–4.5 μm) Cr3C2 grains, NiCr binder phases, and a tiny amount of rare earth oxide additives. The nano-modified multimodal Cr3C2–NiCr coatings maintained a unique structure: submicron Cr3C2 grains embedded in the voids formed by micron Cr3C2 grains, NiCr binder phases and nano Cr3C2 grains imbedded in the voids formed by submicron and micron Cr3C2 grains, and nano Cr3C2 grains are dispersed in NiCr metal binder phases. A few discontinuous elongated amorphous and nanocrystalline phases existed in them. The mechanical interlocking was the dominant bonding mechanism accompanied by local metallurgical bonds. Compared to the conventional coating, the multimodal coating was uniform and dense (porosity was 0.3 ± 0.12%) as well as not obvious lamellar structures, the adhesive strength was 75.32 ± 1.21 MPa, exhibiting a 65 pct increase, and the microhardness was increased by about 18%. The lower porosity and higher strength of nano-modified multimodal structure coating were mainly related to dispersion distribution and synergistic coupling effects of Cr3C2 hard grains with different scales.

Effect of heavy rare-earth (Dy, Tb, Gd) addition on the glass-forming ability and magneto-caloric properties of Fe89Zr7B4 amorphous alloy

In this paper, by adding rare-earth (RE) elements to Fe89Zr7B4 ternary amorphous alloy, we obtained a series of Fe87Zr7B4RE2 (RE = Dy, Tb, Gd) amorphous ribbons to further improve the magnetic refrigeration capacity of the basic alloy. Through the heavy RE element substitutions, the glass-formability of the Fe89Zr7B4 alloy was improved effectively. Besides, the Curie temperature Tc of the alloy system increased from 275 K to 342 K, obtaining a roughly linear correlation between the de Gennes factor and Tc. Through the recombination of ribbons with different Tc values, we designed potential amorphous composites with a "table-like" magnetic entropy change curve under different temperatures. This research promises to deepen understanding of the effect of RE additions on the magneto-caloric properties and enhance the performance of Fe-Zr-B amorphous refrigerants around room temperature.

Rear earth (Re: Sc, Y, and Ce) modified PDCs-SiC ceramics for efficient microwave absorption

Material micromorphological design can effectively enhance electromagnetic properties, thus improving microwave absorption performance. In this paper, Re -SiC ceramics (Re: Sc, Y, Ce) were prepared using PDCs methods. The addition of various rare earth (Sc, Y, and Ce) produced improved microstructural, dielectric, and microwave absorption properties. The results indicate that Sc-SiC ceramic with an appropriately three-dimensional (3D) network structure improves the impedance matching characteristic and dielectric loss, therefore obtaining superior microwave absorption performance. The Sc-SiC ceramic effective absorption bandwidth (EAB) is 3.2 GHz with a thickness of 2.9 mm, and the minimum reflection coefficient (RC min ) is −10.8 dB at the X band. This remarkable microwave absorption property is ascribed to the 3D structure, interface polarization, dipole polarization, conductance loss, multiple reflections, and microwave scattering. Consequently, PDCs-SiC ceramics with appropriate structural decoration can be prospective candidates for application in harsh environments. • Re -SiC ceramics (Re: Sc, Y, Ce) were prepared using PDCs approach. • Sc-SiC ceramic displayed the excellent microwave absorption performance. • Sc-SiC ceramic improved the polarization loss and impedance matching properties.

Influence of Rare Earths Additions on the Microstructure and Hardness of Heat-treated Nanostructured Superalloy Inconel 718.

Influence of Rare Earths Additions on the Microstructure and Hardness of Heat-treated Nanostructured Superalloy Inconel 718.

Effects of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution

The influences of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution are evaluated using mass loss, SEM, 3D morphology and Tafel plot, respectively. The results show that the addition of Ce or Sm or Yb enhances the mechanical property of NAB alloy, and the sizes of κⅠ and κⅡ phases within NAB alloy decrease with adding Ce or Sm or Yb, resulting in the prevention of the propagation of the cracks caused by cavitation erosion initially originated at the phase boundaries between α and κ phases, and finally the cavitation erosion damage significantly decreases with adding Ce or Sm or Yb. The corrosion of NAB alloy in 3.5% NaCl solution can promote the cavitation erosion of NAB alloy, while the corrosion resistance of NAB alloy increases with the addition of Ce or Sm or Yb, and then the cavitation erosion resistance is accordingly improved with the addition of rare earth element.

A New Extruded Mg-6Bi-3Al-1Zn Alloy with Excellent Tensile Properties

Aiming to develop low-cost Mg alloys with good mechanical properties, a new Mg-6Bi-3Al-1Zn (wt.%, BAZ631) alloy having a high ultimate tensile strength of ~402 MPa and an elongation of ~15% was fabricated by single pass extrusion. The as-extruded BAZ631 alloy demonstrates an almost fully dynamic recrystallized microstructure with an average grain size of ~2.9 μm. Moreover, both nano-scale Mg3Bi2 and Mg17Al12 precipitates were found dispersed in the matrix. These excellent mechanical properties are attributed to the combined effects of grain boundary strengthening, dispersion and precipitation strengthening induced by both micro and nanoscale second phase particles, and solid-solution strengthening. This high strength and good ductile Mg-Bi based alloy without rare-earth elements addition is expected to inspire a new alloy design strategy for fabricating high performance Mg products for larger-scale industrial applications.

Regulation mechanism of cooling rate and RE (Ce, Y, Gd) on Mg17Al12 in AZ91 alloy and it's role in fracture process

AZ91-xRE(Ce, Y, Gd, x = 0, 0.3, 0.6, 0.9) alloys with different cooling rates were prepared by die casting. Effects of cooling rate and rare earth elements (Ce, Y and Gd) on Mg17Al12 compound in the alloy and the role of Mg17Al12 compound in fracture process were studied. The results show that the Mg17(Al, Zn)12 compound will be formed in AZ91 alloy, the cooling rate and rare earth elements (Ce, Y and Gd) both can regulate the size, distribution and content of Mg17Al12 compound. The cooling rate can regulate the size and distribution of Mg17Al12 compound in the alloy, but has less effect on the content of Mg17Al12 compound. The addition of rare earth elements can significantly reduce the content of Mg17Al12 compound and refine its size. The reduction effect of Ce on the content of Mg17Al12 compound in alloy is the largest, and the size optimization effect is also the most significant. The effects of Y are the second, and the effects of Gd are relatively poor. The Mg17Al12 compound in alloy is the main crack source and important crack propagation path because of its large size and low strength. Increasing the cooling rate and adding rare earth elements Ce, Y and Gd can make Mg17Al12 compound play a better role in second phase strengthening by optimizing the size, distribution, and content of Mg17Al12 compound.

Structural, electronic, and optical properties of rare-earth-doped SrTiO3 perovskite: A first-principles study

The doping effect of the addition of rare earth elements (Pr, Nd, and Sm) on the mechanical and dielectric properties of the strontium titanate perovskite SrTiO3 was investigated using density functional theory (DFT). The introduction of rare earth elements modifies the structural properties and the charge distribution. Distortion of the Ti–O6 octahedron results in a decreasing trend in the mechanical and electronic properties with increasing nuclear charge numbers of Pr (59), Nd (60), and Sm (62). Rare earth element substitutions move the Fermi-level into the conduction band and change the absorption spectrum by adding peaks at 0.1–0.4 eV.

Study on sliding friction and wear behavior of M50 bearing steel with rare earth addition

This study aims to investigate the influence of rare earth (RE) addition on the friction and wear behavior of M50 bearing steel. The results show that RE addition has little effect on friction coefficient, but can reduce wear volume especially under harsh wear conditions. This mainly results from modification of RE elements to primary carbides. M50 steel without RE addition has bigger proportion slenderer rod-like M2C carbides, which are more likely to cause carbides fracture broken or peeling off, forming bigger wear debris with irregular shape to aggravate the wear. However, M50 steel with RE addition has more spherical MC carbides, which are more easily worn into spherical crowns, forming smaller wear debris which could not increase the subsequent wear.

Effect of rare earth elements on magnetic properties of non-oriented electrical steels

The effect of rare earth elements (REMs) on the magnetic properties of non-oriented electrical steels was studied using industrial trials. The variation of the magnetic properties was discussed in terms of the effect of inclusions, precipitates, grain size, and textures in the steel with and without REMs. Inclusions of MgO·Al2O3-CaS and (Mg, Mn, Ca)S in REMs-free steel were modified into composite ones of MgO·Al2O3-LaAlO3, La2O2S-MgO and (La, Ca)S in the steel with 0.0006% lanthanum, and to (La, Ce)2O2S-CaS-MgO, (Ce, La)S in the steel with 0.0007% lanthanum and 0.0015% cerium. The number density of fine MnS was remarkably decreased by the addition of REMs, leading to an increase in the average grain size. The steel containing 0.0006 wt% lanthanum possessed the best combination of core loss and magnetic induction due to the decrease of micro-sized inclusions and fine MnS, the increase of grain size, and the optimization of recrystallization textures. For the steel with excess REMs addition, the large number density of rare earth sulfides with the size of approximately 1 μm tended to deteriorate the grain size and textures.

Precipitation behavior, mechanical properties, and corrosion resistance of rare earth–modified Al-Zn-Mg-Cu alloys

In this study, we evaluated the microstructure, mechanical properties, and corrosion resistance of four types of 7055 alloys with and without the addition of rare earth elements (Er, Pr) elements. The results show a large number of coarse residual phase particles in the matrix of the 7055 alloy without the addition of rare earth elements, and the area proportion of residual phase is 3.56%; the proportion of low angle grain boundaries (LAGBs) after solid solution treatment is 31.1%. For the three other alloys that incorporate a rare earth element, the number of residual phases in the matrix is decreased, and the proportion of LAGBs is increased. As a result, the 7055 alloy with Pr (7055-Pr alloy) has the lowest number of residual phases, and the area proportion of residual phase is 1.41%; the 7055 alloy with Pr and Er (7055-Pr-Er alloy) has the highest proportion of LAGBs, which is 41.5%. Compared to the untreated 7055 alloy, the elongation and corrosion resistance of the three alloys with a rare earth element are increased. The increase in elongation is due to a reduction in the number of residual phases in the matrix, while the enhanced corrosion resistance is mainly due to the formation of Al3(Er, Zr) particles as a result of adding Er, which could pin the grain boundaries. Thus, the migration of LAGBs to high angle grain boundaries (HAGBs) is inhibited, the LAGBs are retained, and the corrosion resistance of the alloy is enhanced.

The martensitic transformation behavior and shape memory effect of laser powder bed fusion NiTi alloys influenced by rare earth addition

Additively manufactured (AM) has attracted extensive research due to its ability to precisely form NiTi alloys with complex structures compared to conventional fabrication processes. However, the strong-plastic mismatch, poor shape memory effect (SME) and functional properties severely limit the wide application of AM-NiTi alloys. Rare earth oxides are common additives to improve the mechanical properties of alloys. This paper is the first to report the effect of different additions of CeO2 (0.03% CeO2, 0.3% CeO2 and 3% CeO2) on the properties of NiTi alloys prepared by laser powder bed fusion (LPBF) technology. The results showed that different amounts of CeO2 seriously affect the transition temperatures (TTs), SME and mechanical strength of LPBF-NiTi alloys. The change of TTs is mainly related to the precipitates formed after the addition of CeO2. The formation of NiCe reduces the Ni content in the matrix and thus increases the TTs, while the generation of CeTi2O6 reduces the content of Ti in the matrix, resulting in a decrease in TTs. The improvement of mechanical properties is mainly attributed to the grain refinement strengthening, precipitate-dislocation interaction and solid solution strengthening after rare earth addition. More significantly, the addition of an appropriate amount of CeO2 (0.03% CeO2) promoted the grain order of LPBF-NiTi alloys and improved the yield strength and SME.