Influence Of Rare Earth Addition Research Articles

Influence of rare earth addition on microstructures and mechanical properties of high-pressure die casting Mg–8Zn–6Al alloy

Effects of 3 wt% RE (rare earth) addition on microstructures and mechanical properties of a high-pressure die casting Mg–8Zn–6Al (ZA86) alloy before and after aging treatment was thoroughly studied in this work. Microstructural characterizations present that RE addition has indiscernible influence on the well-defined dendrite structure and grain size, but would additionally introduce Al-RE intermetallic phases, which were identified as Al3RE and Al11RE. Simultaneously, two groups of Mg–Al–Zn ternary phases were detected in alloys with/without RE addition, while their volume fraction was clearly reduced by RE addition. After aging at 90 °C for 320 h, a large density of precipitates were observed particularly near grain/cell boundaries, and were identified as MgZn2, Mg4Zn7, and I-phase. Although RE addition seems to have no influence on the components of precipitates, it obviously improves their volume fraction and slightly increases their size. Finally, the yield strength of the ZA86 alloy after aging was improved by ∼33 MPa by RE addition. Therefore, the die cat ZA86 alloy exhibits high-strength and certain precipitation strengthening ability, and RE addition can significantly enhance the precipitation strengthening, accomplishing the highest yield strength in the reported HPDC magnesium alloys, being ∼267 MPa.

Influence of rare earth addition on the properties of AA6351 hybrid composites

Nowadays, the effect of the rare earth addition on the performance of aluminium matrix composites is a major interest for many researchers. The present research work emphasis is on the study of the effect of praseodymium oxide (rare earth element) addition on the performance of AA6351 hybrid composites. Silicon carbide and rice husk ash in the weight proportions of 6:2 were ball-milled with various weight percentages (0.4%, 0.8%, and 1.2%) of praseodymium oxide to have a consistent microstructure and combined density equivalent to the AA6351 matrix alloy. Further, AA6351 hybrid composites with the ball-milled reinforcement of silicon carbide, rice husk ash, and praseodymium oxide were produced using stir-casting technique. Physical, microstructural, mechanical, and tribological characterization were done to study the impact of praseodymium oxide addition on the developed hybrid composites. An increment of 2.61% in the density, 49.40% in the microhardness, and 19.78% in the ultimate tensile strength was recorded with the incorporation of 1.2 weight percentage of praseodymium oxide in the AA6351 hybrid composites. The wear rate of the developed composites also improved by 32.92% with the addition of praseodymium oxide. The results exhibited a remarkable improvement in the performance of the AA6351 hybrid composites with the addition of rare earth element.

Influence of Rare Earth Additions to an Inconel 718 Alloy

AbstractThis work analyzes the effect of rare earth additions to an Inconel 718 superalloy; for this purpose, two 8 kg ingots of a commercial composition of Inconel 718 were made in a vacuum induction furnace. One of them (In718) with the base composition and the other one (In718RE) with an addition of 0.04wt% of mischmetal (rare earths alloy based on cerium and lanthanum). Both alloys were cast into metallic molds into the vacuum chamber and let to solidify. The alloys were then solubilized for two hours at 1155 °C to eliminate deleterious phases, rolled at 1100 °C to get a reduction of 50% in thickness, then aged for 16 hours at 720 °C and 620 °C by 8 hours each. A complete microstructural characterization was undertaken by optical and electronic (SEM and TEM) microscopy and X-ray diffraction. Mechanical characterization was done by hardness tests, tensile and Charpy impact tests. Results show a slight improvement of the tensile and hardness values for the alloy with rare earth additions. However, no notorious difference was observed during the impact tests, since both alloys show the same values. These mechanical results are discussed in terms of the obtained microstructure. Both alloys are mainly composed by γ, γ´, γ´´ and carbides. It was observed that primary carbides nucleate rare earth particles; therefore, higher number of carbides and of larger size (according to a size distribution) are observed in the alloy with rare earth additions. The presence of such carbides prevents the grain growth during the thermomechanical processing which in turn improve the mechanical properties.

Influence of rare earth metals on mechanisms of localised corrosion induced by inclusions in Zr-Ti deoxidised low alloy steel

The influence of rare earth addition on the mechanism of localised corrosion induced by inclusions in Zr-Ti deoxidised steel was investigated in a simulated marine environment. Inclusion size and composition changed after rare earth addition, profoundly affecting the localised corrosion. Current sensing atomic force microscopy results showed that no galvanic couple formed between inclusions and matrix owing to the insulating property of different inclusions. Matrix dissolution resulting from the microcrevices and lattice distortion surrounding ZrO2-Ti2O3-Al2O3 inclusions initiated localised corrosion in Zr-Ti deoxidised steel. After adding RE, localised corrosion was induced by dissolution of the (RE)2O2S-(RE)xSy part of the inclusion.

Influence of rare earth addition in cobalt ferrite thin films obtained by pulsed laser deposition

The influence of rare earth (RE = Dy, Gd, Yb) ion doping on the structural, magnetic and optical properties of cobalt ferrite thin films was studied. CoFe2-xRExO4 (x = 0.01; 0.03; 0.05; 0.1; 0.2; 0.3) films were obtained by pulsed laser deposition on silicon substrates. The X-ray diffraction and Raman spectroscopy results on the bulk materials, which were used as targets during deposition, revealed the formation of residual phases as the concentration of RE dopant was increased. However, the annealed thin films presented diffraction lines and vibrational modes corresponding only to cobalt ferrite. A lower crystallinity of the deposited samples was observed when higher RE concentrations were used. Due to the substitution of Fe by RE elements which possess large ionic radii, the lattice parameter of the thin films presented a monotonous increase. The magnetic response of the nanostructures was correlated to the magnetic moment of the RE dopant and to the structural properties of the films. The optical bandgaps derived from the reflectance spectra presented an increasing trend as the Yb and Dy concentrations were augmented.

Influence of Rare Earth Additions on the Microstructure and Mechanical Properties of Al7Si0.3Mg Alloys Processed by Semi-Solid Die Casting and Gravity Die Casting

Microstructures with fine globular grains and refined eutectic structures are important to enhance the mechanical properties of A356 alloys processed by semi-solid and gravity die casting. Rare earth (RE) additions have been shown to be capable of refining both the α-Al particles as well as modify the eutectic phase of alloys. In semi-solid die casting, Al7Si0.3Mg alloys with RE concentrations (0, 0.1 and 0.4 wt.%) were used to prepare semi-solid slurries using the SEED (Swirling Enthalpy Equilibrium Device) method, and subsequently semi-solid die cast. The same compositions of alloys were also applied to gravity die casting. The microstructure and mechanical properties of castings in two processes have been characterized. Compared to the grains produced in gravity die casting, globular grains with small size (260 μm) in the semi-solid die casting significantly enhance the UTS and elongation of alloys. Although the size of grains had no change with increasing RE concentrations in alloys. The Al-Si eutectics were changed to refined morphology with the 0.1 wt.% RE addition, which enhanced the ductility of alloys in two processes. When increasing the RE addition to 0.4 wt.%, the RE-rich phases precipitated at grain boundaries, which decreased the UTS and elongation of alloys.

Effect of Rare Earth Oxide Addition on the Microstructure and Properties of Ultrafine Grain W-20Cu Composites

Ultrafine W-20wt%Cu (W-20Cu) powders doped with 0 wt%∼0.8 wt% rare earth oxides Ce0.8Sm0.2O1.9 (SDC) were synthesized by the EDTA-citrate method using ammonium metatungstate and copper nitrate as raw materials, and the resultant powders were pressed and sintered at 1250 °C in H2 atmosphere for 2 h to obtain SDC/W-20Cu composites. Morphology of the SDC/W-20Cu powders and microstructure of the sintered SDC/W-20Cu composites were observed by SEM, and density, physical and mechanical property of sintered SDC/W-20Cu composites were also tested to investigate the influence of rare earth addition. The results show that the SDC/W-20Cu powders are irregular in shape with particle size ranging from 100 nm to 200 nm. The addition of SDC has slight influence on the electrical conductivity, but obviously refines the grain size and improves the mechanical properties of the W-20Cu composites. The sintered SDC/W-20Cu samples have relative density above 97%. Bending strength and micro-hardness HV of the SDC/W-20Cu specimens are 1128 MPa and 3180 MPa with the addition of 0.6 wt% SDC, respectively, and the highest tensile strength reaches 580 MPa and 258 MPa at room temperature and 600°C, respectively.

Effect of cerium addition on microstructure and mechanical properties of high-strength Fe85Cr4Mo8V2C1 cast steel

This work presents an investigation on the influence of rare earth additions (Ce) on the microstructure and mechanical properties of a cast Fe85Cr4Mo8V2C1 (element contents in wt%) tool steel. The applied relatively high solidification rate during the casting process promotes the formation of non-equilibrium phases such as martensite, retained austenite as well as a fine network-like structure of complex carbides. This combination of phases and their morphology results in excellent mechanical properties already in the as-cast state.Cerium additions induce a change in phase formation and resulting mechanical properties. Besides morphological and quantitative changes of the main constituent phases, novel carbo-oxide and carbide phases are formed. To investigate this microstructural phenomenon, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX) were applied.Altogether, the addition of small amounts of the rare earth element cerium together with a tailored casting process results in enhanced mechanical properties compared to the Fe85Cr4Mo8V2C1 alloy and offers new possibilities to obtain high-strength and simultaneously adequate ductile cast steels for advanced tool design.

Influence of rare-earth addition on the long-period stacking ordered phase in cast Mg–Y–Zn alloys

The microstructure and thermal stability of the Mg97Y2Zn1 (at.%) alloy, modified with the addition of 0.5 at.% of gadolinium or neodymium, have been examined by synchrotron radiation diffraction during in situ differential scanning calorimetry. The microstructure of the three alloys consists of magnesium dendrites with the Long Period Stacking Ordered (LPSO) phase at interdendritic regions. Rare-earth atoms substitute yttrium atoms in the LPSO phase, promoting the formation of the 14H structure. Lattice parameters of the LPSO do not change significantly with the rare-earth addition. However, they reduce the melting point of the LPSO phase, especially in the case of neodymium addition.

Influence of Rare Earth Addition on Texture Development during Static Recrystallization and Mechanical Behaviour of Magnesium Alloy Sheets

The role of rare earth addition on the microstructure and texture during recrystallization of cold rolled sheets is investigated by a comparative study of pure Mg, Mg-3Y and Mg1.5Nd sheets. In pure Mg, nucleation occurs mainly at shear bands which results in a texture weakening. The basal-type texture re-strengthens rapidly during grain growth of the pure Mg sheet. In contrast, in the Mg-RE alloys the weaker texture formed during early recrystallization strage is retained during further annealing due to retarded grain growth. Uni-axial tensile and Erichsen tests show that ductility and sheet formability are significantly improved by addition of rare earth elements.

Influence of rare earth additives and boron component on electrical conductivity of sodium rare earth borate glasses

Abstract Sodium rare earth borate glasses (Na2O)35.7(RE2O3)7.2(B2O3)57.1 (RE = Sm, Gd, Dy, Ho, Y, Er, and Yb), were prepared from a mixture of Na2CO3, RE2O3 and B2O3, and their properties as an Na+ ionic conductor were investigated. Density increased with increasing atomic weight of RE. Crystallization temperature and crystal melting temperature of the present borate system was lower than that of the previously reported silicate and germanate system. Results of the 11B NMR measurement suggested that half of all boron atoms are coordinated by four oxide ions to give a [BO4] tetrahedral unit and the others are coordinated by three oxide ions to give a [BO3] planar triangular unit. The electrical conductivity slightly decreased with increasing the ionic radius of RE3+. (Na2O)35.7(Y2O3)7.2(B2O3)57.1 glass exhibited the electrical conductivity which is about one order of magnitude lower than those of the previously reported (Na2O)35.7(Y2O3)7.2(SiO2)57.1 and (Na2O)35.7(Y2O3)7.2(GeO2)57.1 glasses. It was assumed that this lower electrical conductivity is due to the lower content of Na+ ions as conduction species in the former glass, compared with the latter two glasses.

Influence of rare-earth addition on dielectric properties and relaxor behavior of barium zirconium titanate thin films

Ba ( 1 – 3 / 2 x ) M x Zr 0.20 Ti 0.80 O 3 (M=La, Ce, and Dy; x=0, 0.005, 0.01, 0.02, and 0.05) thin films are successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method, and the influence of the rare-earth ions content on the microstructure, dielectric properties, and phase transformation behavior is investigated in detail. As a result, the rare-earth ions with various ionic radii enter the perovskite lattice to substitute for A-site Ba2+ ions and inhibit the grain growth. With the increase in rare-earth ions concentration, the dielectric constant, dielectric loss, tunability, and leakage current density of Ba(1–3/2x)MxZr0.20Ti0.80O3 thin films decreased. Simultaneously the temperature of maximum of dielectric constant shifts to the lower temperature and relaxor phase transition behavior is observed due to the rare-earth ions substitution. And the degree of the relaxor behavior is enhanced with the increase in rare-earth ions content and ionic radius.

Influence of rare-earth additives (La, Sm and Dy) on the microstructure and dielectric properties of doped BaTiO3 ceramics

A series of La/Mn, Sm/Mn and Dy/Mn codoped BaTiO3 samples were prepared by the conventional solid state procedure with dopant concentrations ranging from 0.1 up to 2.0 at%. The specimens were sintered at 1320?C and 1350?C in an air atmosphere for two hours. The low doped samples demonstrated a mainly uniform and homogeneous microstructure with average grain sizes ranging from 0.3 ?m to 5.0 ?m. The appearance of secondary abnormal grains in the fine grain matrix and core-shell structure were observed in highly doped La/BaTiO3 and Dy/BaTiO3 sintered at 1350?C. The low doped samples, sintered at 1350?C, display a high value of dielectric permittivity at room temperature, 6800 for Sm/BaTiO3, 5900 for Dy/BaTiO3 and 3100 for La/BaTiO3. A nearly flat permittivity-response was obtained in specimens with 2.0 at% additive content. Using a modified Curie-Weiss law the Curie-like constant C? and a critical exponent ? were calculated. The obtained values of ? pointed out the diffuse phase transformation in heavily doped BaTiO3 samples.

Influence of rare-earth addition on microstructure and dielectric behavior of Ba 0.6Sr 0.4TiO 3 ceramics

Ba 0.6Sr 0.4TiO 3 (BST) ceramics with 0.5 mol% various trivalent rare-earth additions prepared by a solid-state route are investigated. A strong correlation is observed between the microstructure, dielectric properties and rare-earth element dopant. The results display that comparing with the lattice constants of undoped and doped rare-earth BST, the structure transforms from cubic to tetragonal structure. In addition, the dopant improves the tetragonal distortion with the ionic radius of rare earth decreasing, and then deteriorates it with further decreasing. Large ions rare-earth additions effectively suppress the grain growth of BST. It is found that the temperature-permittivity characteristics for the BSTR (R, namely, rare earth) system could be controlled using various rare-earth elements. Especially, such as Sm, Eu, Gd dopants are effective to satisfy the tunable microwave devices application due to the decrease of permittivity and the improvement of dissipation factors of BST ceramic with the accompanying high-tunability.

Effect of rare earth elements on microstructure and oxidation behaviour in TIG weldments of AISI 316L stainless steel

The influence of rare earth addition in weld metal, on the microstructure and oxidation behaviour of AISI 316L stainless steel in dry air under isothermal condition at 973 K for 240 h is reported. Rare earth metal (REM) doped weld metal zone exhibits better oxidation resistance during isothermal holding as compared to base metal and undoped weld metal zone of 316L. Presence of both Ce and Nb in weld metal shows superior oxidation resistance than with Ce alone. TIG weld microstructures are presented by optical microscopy. The morphologies of the scales and nature of their adherence to the alloy substrates, and scale spallation have been characterized by SEM and EDAX.

The influence of rare earth metals on the structure of some rapidly solidified Ge- and Si-based alloys

Ge-rich amorphous alloys containing up to 70 at.% Ge were produced by the optimization of the Al, Cr and RE (RE: rare earth metals) content. Contrary to the Ge-based alloys, no positive influence of RE additions on the glass forming ability (GFA) of the Si–Al–TM and Si–Al alloys (TM: transition metals) was found. As no split of the first broad peak is seen in the X-ray diffraction patterns taken from the amorphous phase of the Ge–Al–RE alloys, one can suggest that such a feature observed in the Ge–Al–TM and Ge–Al–TM–RE alloys is affected by the presence of 3d TM. Peritectic-type phase transformation, amorphous phase + unknown crystalline phase 1→ unknown crystalline phase 2 , was observed in the Ge 60Al 25La 15 alloy and studied. The metastable crystalline phase 2 (Ge 12Al 5La 3) was found to have a tetragonal lattice with lattice parameters of a=0.559 nm and c=0.528 nm .

Dielectric properties of rare earth doped (Sr,Ba)Nb 2O 6 Ceramics

The influence of rare earth addition on the microstructure and phase transition of Sr 0·61Ba 0·39Nb 2O 6 ceramics was investigated. Sr 0·61Ba 0·39Nb 2O 6 undoped and doped with 0·3 and 1·0 wt% La 2O 3 and 0·3 wt% Nd 2O 3 were prepared by the conventional ceramic method. Dielectric measurements were performed in order to characterize the phase transition in these ceramics. The addition of RE elements decreased the maximum dielectric constant (ε MAX ) and its correspondent temperature ( T MAX) and increased the dielectric losses in all studied samples. A peak broadening and an increasingly Curie–Weiss behavior was verified for a La, while an inverse dependence occurred for Nd doping.

Effect of Rare‐Earth Additives on Electromechanical Properties of Modified Lead Titanate Ceramics

The influence of rare‐earth additives, such as La, Nd, Sm, and Gd, and poling conditions on the electromechanical properties of (Pb1−3x/2Lnx)(Ti0.98Mn0.02)O3 compositions, x= 0.04–0.12, were investigated. The type and amount of additive were found to affect the lattice anisotropy, dielectric constant, and electromechanical properties. A large electromechanical anisotropy (kt/kp) could be obtained in 10 mol% Sm‐modified and 8 mol% Gd‐modified lead titanate ceramics, and seemed to correlate to a low Poisson's ratio.

Influence of rare earth additions on rheological behaviour of Al–5Cu alloy in solid-liquid coexistence zone

A rheological model was constructed and the influence of rare earth (RE) additions on the rheological behaviour of an Al–5 wt-%Cu alloy in the solid-liquid coexistence zone (SLCZ) was investigated, using an apparatus specially designed by the authors for studying the rheological properties of aluminium alloys. It was found that the rheological behaviour of an Al–5Cu alloy can be described by a combination model (the series arrangement of the Hooke model with the Kelvin and Bingham models). It was shown that RE additions can increase the values of the rheological parameters (shear modulus G, viscosity η, and yield strength τs) of Al–5Cu in the SLCZ to some extent, and can decrease the temperature at which the retardation time η2/G2 of the Kelvin model is a minimum and the Kelvin model temperature TK. Also, RE additions can reduce the effective temperature zone ∆TK of the Kelvin model.MST/1357

Influence of rare earth additions on rheological behaviour of Al–5Cu alloy in solid-liquid coexistence zone

AbstractA rheological model was constructed and the influence of rare earth (RE) additions on the rheological behaviour of an Al–5 wt-%Cu alloy in the solid-liquid coexistence zone (SLCZ) was investigated, using an apparatus specially designed by the authors for studying the rheological properties of aluminium alloys. It was found that the rheological behaviour of an Al–5Cu alloy can be described by a combination model (the series arrangement of the Hooke model with the Kelvin and Bingham models). It was shown that RE additions can increase the values of the rheological parameters (shear modulus G, viscosity η, and yield strength τs) of Al–5Cu in the SLCZ to some extent, and can decrease the temperature at which the retardation time η2/G2 of the Kelvin model is a minimum and the Kelvin model temperature TK. Also, RE additions can reduce the effective temperature zone ∆TK of the Kelvin model.MST/1357