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The effects of mischmetal addition and hot working on the enhancement of microstructure and mechanical properties of Mg–Ni alloys were studied. It was revealed that grain refinement could be achiev...

This 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.

The combined addition of small amounts of Ca and Y to Mg–Al–Zn alloys has recently been found to greatly improve the ignition resistance, corrosion resistance, and mechanical properties of these alloys. However, Mg–Al–Zn–Ca–Y alloys with high Al content show poor extrudability, which is an obstacle to their use as extruded components in industrial applications. This study aims to improve the extrudability of a Mg–Al–Zn–Ca–Y alloy through the addition of a small amount of mischmetal (MM). To this end, a trace amount (0.5 wt%) of Ce-rich MM is added to a Mg–9Al–0.8Zn–0.9Ca–0.6Y (AZXW9110) alloy. MM addition leads to significant grain refinement of the homogenized billet, from 326 to 180 μm. When the MM-added alloy is extruded into a sheet at 350 °C with an extrusion ratio of 22.9, the maximum ram speed at which it is extrudable without the occurrence of hot cracking is 12 mm/s, substantially higher than the 2 mm/s possible without MM addition. The Ce and La atoms decomposed from the MM are dissolved in the Mg17Al12, Al8Mn4Y, Al2Ca, and Al2Y phases, apparently leading to an increase in the thermal stability of the phases and, consequently, to an improvement in the AZXW9110 alloy’s extrudability. At ram speeds above 2 mm/s, many small-sized cracks form at the edges of the extruded AZXW9110–0.5MM sheets. As the ram speed increases up to 6 mm/s, the number density of edge cracks gradually increases while their average spacing decreases, but beyond 6 mm/s both remain almost unchanged.

The present study investigated the effect of Gd on the microstructures and mechanical properties of permanent mould cast Mg-4Al-5RE (wt%) (where RE represents La-Ce mischmetal) alloy. Coarse grains and acicular Al11RE3 phases in Mg-4Al-5RE alloy are successfully refined by the addition of 0.66 wt% Gd. The average grain size is dramatically decreased from 493.9 μm to 205.8 μm, and the acicular Al11RE3 phase is modified to rod-like sharp with a pronouncedly decreased average length from 22.0 μm to 3.8 μm. The modified microstructures are attributed to the formation of Al2(Gd, RE) particles, which act as nucleation sites for both α-Mg and Al11RE3. Eventually, the modified alloy exhibits dramatically enhanced yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) about 12%, 23% and 48%, respectively.

The article presents the results of primary crystallization, wear resistance and SEM studies of chromium cast iron inoculated with ferrotitanium and rare earth elements as a mischmetal inoculating mixture. Thermal-derivative analysis method was used to conduct studies of primary crystallization in two types of testers, namely ATD-C and ATD-Is, reflecting two different cooling speeds. Wear resistance tests were performed with the use of modified pin-on-disk method on Tribotester 3-POD device, where the samples were moving in circular motion in metal-mineral friction system. Silicon carbide was used as a counter sample. The studies allowed to determine the influence of selected inoculants on the microstructure and wear resistance of the studied samples. All characteristic crystallization temperatures of samples casted into ATD-Is testers increased, as well as wear resistance of each inoculated samples compared to the non-inoculated sample. It was proven that TiC and REE compounds are effective inoculants for chromium carbides and that REE compounds can work as underlay for TiC crystallization.

A Ca-containing Mg-4Zn-1MM(mischmetal)-0.1Ca (wt.%, ZEX4101) alloy sheet shows Index Erichsen value of 6.7 mm, which is better than commercial Mg alloy sheets. The good formability is attributed to its weakened basal texture, in which the intensity of the (0001) poles of the recrystallized grains spreads towards the transverse direction. By monitoring the microstructural evolution during the hot rolling and the solution treatment, we found that Ca addition hinders the formation of strong basal texture during the rolling. During the subsequent solution treatment, static recrystallization mainly proceeds by the growth of dynamically recrystallized grains, and then the weak texture feature of the dynamically recrystallized grains is maintained in the ZEX4101 alloy sheet. It is hypothesized that co-segregation of Zn and Ca atoms to the grain boundaries prevents the rotation of the (0001) poles of the dynamically recrystallized grains toward the sheet normal direction, resulting in the development of weak basal texture in the ZEX4101 alloy sheet.

The relative potential difference can be treated as an index of local corrosion of alloys. Since local corrosion is driven by the micro-galvanic coupling, which is consist of the micro-constituent phases and the matrix. They present distinct potential difference normally. In the present work, the relationship between the Volta potential and the corrosion effect of the dominated intermetallic phase in the AZ91 Mg alloy with (La, Ce) MM addition was investigated. A multiscale approach coupling global and local measurements was used to study the corrosion behavior of the alloy and its intermetallic phase. Results showed that the microstructure of AZ91 Mg alloy with (La, Ce) MM addition was complex, with the presence of Al4(La, Ce) phases in acicular or rod shape, a small number of Al8Mn4Ce, β-Mg17Al12 and α-Mg solid solution. In this case, the improved corrosion resistance of the alloy was achieved. Scanning Kelvin probe force microscopy (SKPFM) analysis revealed that all the intermetallics were noble comparing with the α-Mg solid solution. In-situ electrochemical atomic force microscopy (EC-AFM) observation for the initial stages of corrosion showed the α-Mg matrix surrounded by β-Mg17Al12 or Al8Mn4Ce was susceptible to pitting corrosion. No noticeable corrosion occurred at the α-Mg adjacent to Al4(La,Ce) phase, in spite of the relatively higher difference of Volta potential between Al4(La,Ce) phase and the matrix. Volta potential is insufficient to determine whether the phase is an effective cathode or anode.

LaNi5-type alloys are commercial materials for the negative electrode in Ni-MH rechargeable batteries. Partial substitution of La by mischmetal (Mm) and of Ni by elements like Co, Al, and Mn significantly improve the cycle stability and high-rate discharge capacity of the electrodes. The partial substitution of Ni by Cu was studied previously for several selected ternary alloys with a special focus on crystal structure change upon substitution and gas phase hydrogen absorption. We present in this paper the results of the study of the electrochemical activation, discharge kinetics, equilibrium charge/discharge, and cycle life of electrodes made from four different LaNi5-xCux (x = 0.1, 0.5, 0.9, 1) alloys in order to provide full insights into utilization of these alloys.

Mg-Zn-Zr (ZK) alloys exhibit notably high mechanical strength amongst all magnesium alloy grades. However, due to the formation of low melting point Mg3Zn7-precipitates, these alloys are susceptible to hot cracking, thus compromising their metallurgical processing. The addition of rare earths to ZK alloys is an alternative to form higher melting point intermetallic compounds, speed up dynamic recrystallization, refine grain size, enhance corrosion resistance and extend the service temperature due to improved creep resistance. This work deals with the effect of Ce-base mischmetal addition on the hot rolling behaviour of as-cast ZK60 alloy. The microstructure investigation conducted using electron microscopy and X-Ray diffraction shows that precipitation of Mg7Zn3 intermetallics occur during hot rolling, whereas no further precipitation is observed for the ZK60-Mm alloys. The fragmentation of the intermetallic compounds occur during hot rolling and finer particles of Mg7Zn3 are observed for the ZK60, whereas Mg7Zn3 and MgZn2Ce intermetallics are formed in the alloy modified with mischmetal addition. A higher fraction of dynamically recrystallized grains is observed for the ZK60-Mm in comparison to the ZK60. Continuous recrystallization takes place in ZK60 with the formation of sub-grains near to the intermetallics and the addition of mischmetal promotes the occurrence of discontinuous recrystallization with the nucleation of new grains close to the precipitates. The mechanical strength and, in particular, the ductility of the hot-rolled alloys are notably improved when compared to the same alloys in the as-cast condition. The mechanical strength is, however, higher for the ZK60 alloy. Less solid solution strengthening, softer MgZn2Ce intermetallics and more extensive recrystallization contribute to reduce the mechanical strength of ZK60-Mm. Failure in both alloys are initiated at coarse intermetallics and propagate through intermetallic-rich regions.

Alloying of Mg with rare-earth (RE) elements proved to be beneficial for their in-vitro and in-vivo performance. In this work, a novel WN43 (Mg-4 wt%Y-3 wt%Nd) alloy with a well-defined composition was prepared, where, unlike in the commercial WE43 alloy, the possibly harmful RE mischmetal was substituted by less toxic Nd. A modern spark plasma sintering (SPS) technique was used to effectively produce WN43 samples from atomized powders. Sintering temperatures of 400 °C – 550 °C and holding times of 3 or 10 min were used and well-compacted final materials were successfully prepared. It was shown that a superior combination of corrosion and mechanical properties was attained in the samples sintered at 500 °C and 550 °C, while the effect of sintering time was rather negligible. The performance of this material was exceptional within the group of Mg alloys prepared by powder metallurgy and comparable with conventionally prepared alloys. Moreover, it was shown that a great variety of mechanical and corrosion characteristics can be obtained by altering the SPS parameters so as to fulfill case-specific requirements typical of biomedical materials. Consequently, the novel WN43 alloy prepared by SPS seems to be a particularly suitable material for biomedical use.

Journal of magnesium and alloys 9(5), 1782-1796 (2021). doi:10.1016/j.jma.2021.04.012, Published by Elsevier, Amsterdam [u.a.]

This study investigated the high-temperature mechanical properties and collaborative working mechanism of zinc-5% aluminum-mixed mischmetal alloy-coated steel strand cables (M-C cables) and internal steel wires by numerical analysis, based on the experimental data for the high-temperature mechanical properties of steel wire. The high-temperature mechanical properties of zinc-5% aluminum-mixed mischmetal alloy-coated steel (M-C steel) with round and Z-shape cross-section shapes were studied in the temperature range of 30–800 °C using the constant temperature loading test method. The two-stage Ramberg-Osgood model for M-C steel wires at elevated temperatures is proposed for modeling of the M-C steel wires. Furthermore, the equations for the reduction in the nominal yield strength, elastic modulus and ultimate strength for M-C steel wires at elevated temperatures are proposed. Numerical analysis and investigation of the high-temperature mechanical properties of normal M-C cables and locked M-C cables under eight temperature conditions are carried out. Based on the high-temperature constitutive relationship of the round and Z-shaped M-C steel wires obtained experimentally, the thermostatic drawing process is simulated at different temperatures for two types of M-C cables. The high-temperature stress-strain relationship between the two and the relevant high-temperature mechanical performance index were obtained. According to the numerical simulation results, the energy, contact stress distribution and radial displacement deformation of M-C cables under the different temperature condition were evaluated and analyzed. The collaborative working mechanism of M-C cabled affected by temperature was revealed.

Microstructure and mechanical properties of in situ Mg2Si/AZ91 composites fabricated using silica fume as the Si source were investigated. The composites contained α-Mg, network Mg17Al12, lamellar Mg17Al12, coarse polygonal Mg2Si and needle-type Mg2Si. Mischmetal modification eliminated the coarse polygonal Mg2Si and resulted in a decreased amount of lamellar Mg17Al12 and refined matrix grain size. Solution and aging treatment made the network Mg17Al12 transform into lamellar Mg17Al12. As the volume fraction of Mg2Si increased, the matrix grain size decreased, the amount of Mg17Al12 increased, and more Mg17Al12 precipitated in grain interiors as a result of the increased Al/Mg ratio caused by increasing the amount of Mg2Si. The tensile strength and elastic modulus were much higher for the modified composites than for the unmodified one and increased by both increasing the volume fraction of Mg2Si and performing aging treatment. The composites failed in a quasi-cleavage fracture mode, and coarse polygonal Mg2Si phases were responsible for the lowest ductility of the unmodified composite. The highest UTS of 291.55 MPa obtained is much higher than those reported so far by using fly ash as the Si source, indicating that silica fume is more suitable as the Si source to synthesize Mg2Si/AZ91 composites.

Magnesium alloys are important alternatives for structural weight reduction due to their low density and good specific mechanical strength. Among the magnesium alloys, the ZK type exhibits the highest mechanical strength. However, it has limitations on hot working or welding owing to the presence of intermetallics with low melting point and consequently susceptibility to hot crack formation. The addition of rare earths tends to form intermetallics with higher melting points, thus inhibiting the formation of hot cracks, as well as building up thin and dense surface films that improve corrosion resistance. This work studies the addition of 1.5% wt. of mischmetal (Mm) to the ZK60 alloy, and then demonstrates the effects of the casting process with mechanical mixing in the semi-solid state. The alloys produced were: ZK60 and ZK60–1.5 wt%Mm manufactured by conventional casting and rheocast ZK60–1.5 wt%Mm produced with mechanical mixing in the semi-solid state. The casting and cooling methods result in defect-free and chemically homogeneous materials, and the mechanical mixing provides a homogeneous microstructure with globular grains. The mechanical strength was though higher for the ZK60 alloy due to its increased solute content within the Mg-matrix and the smaller quantity of intermetallics that builds up an intermittent network. The Mg7Zn3 intermetallic, which is the main precipitate for ZK60 alloy, has hardness 20% higher than the MgZn2Ce intermetallic that is precipitated with the mischmetal addition and partly removes solute from the Mg-solid solution.

Coercivity enhancement of hot-deformed NdFeB magnets made from commercially available NdFeB powders doped with Ce-containing alloys is demonstrated. By doping (Pr71Nd27Ce2)70Cu30 powders, where Pr71Nd27Ce2 is a commercial mischmetal, the hot-deformed magnets exhibit significant enhancement of coercivity from 15.0 kOe to 19.0 kOe, and it can reach 20.1 kOe by doping higher Ce-content (Pr71Nd9Ce20)70Cu30 powders, yet sustains high energy product. The magnetic isolation effect with Ce-containing phase in the grain boundary and the microstructure refinement lead to coercivity enhancement. This study provides an economic way to enhance coercivity of hot deformed NdFeB magnets without using heavy rare earth.

This work presents results on the effect of mischmetal (MM) content on the magnetic properties, phase formation, microstructure, and intergranular interactions in MM12+xFe78-xCo2B6 (x = 0, 4, 8) magnets. The MM-FeCo-B magnets have been prepared by Spark Plasma Sintering method from powders obtained by grinding precursor nanocrystalline ribbons. A significant increase in coercivity of almost 50%, from 5.4 kOe to 10.2 kOe, has been obtained when the MM content increased from 12 at% to 20 at%, while the remanence decreased with about 30%, from 100.3 to 74.45 emu/g. X-ray diffractograms analysis indicates that for a MM content higher than 12%, in addition to the 2: 14: 1 main phase, secondary phases are formed, the amount of which increases when the MM content increases. Electron microscopy investigations have shown that the secondary phases accumulate at the boundaries of the main phase grains. In the case of the magnet with 20 at% MM content the main phase grains are completely isolated. As a result, the magnets show a weakening of the exchange interaction, explaining thus the increase in coercivity. The best magnetic properties, such as coercivity of about 8.7 kOe and maximum energy product of 11.19 MGOe, have been obtained for the magnet with 16% MM content, which is promising for practical applications in terms of filling the gap between ferrites and Nd-Fe-B magnets.

The interface associativity and energy absorption capability of composite structure with anti-vibration porous Al-MM (cerium-rich mischmetal) alloy core and iron alloy skin were investigated. Porous aluminum core/iron alloy skin structures were fabricated considering an iron alloy tube as its shell and closed-cell porous Al-MM alloy as its core. A peeling experiment was carried out to calculate the capacity of interfacial bonding and a compression test was carried out to determine the energy absorption capability. The results showed that the addition of MM significantly enhanced both the interfacial bonding and the energy absorption capacity.

Mischmetal-Fe-B ribbons were prepared by melt-spinning method, and industrial mischetal with low purity was selected as the raw material. By introducing La and employing nonequilibrium technology, we successfully avoid the formation of CeFe 2 phase, which decreases magnetic performance greatly. Considerable energy product and intrinsic coercivity were achieved in (MM) 2.4 Fe 14 B, which are 80.69 kJ/m 3 and 500 kA/m, respectively. Phase composition and magnetization process of all the samples were investigated. Strong pinning effect was found in all rare-earth-rich samples and was identified as a crucial factor to obtain high coercivity in ribbons compared with the sintered magnets. The Henkel plot is also measured to investigate the intergrain interaction and the results show a strong exchange coupling between grains. Based on these results, the difference in magnetic performance between nanocrystalline ribbons and sintered magnets can be explained.

The thermal conductivities of quaternary Mg-Zn-Ca-MM alloys have been investigated by evaluating the effect of MM on Mg-4Zn-0.5Ca alloys, with an emphasis to develop a new Mg alloy without compromising thermal conductivity, process-ability and mechanical property. As a result, the thermal conductivity of 0.5 wt.% MM-added Mg-Zn-Ca alloy was almost same as that of MM-free Mg-Zn-Ca alloy. However, with further increasing MM contents, thermal conductivities of MM-added alloys decreased. The tensile yield strength was improved with increasing MM contents. In addition, the average spiral flow lengths of Mg-Zn-Ca-xMM alloys were almost same levels with Mg-Zn-Ca alloy.

Solution treatments (T4) at 380 °C for 16 h and 500 °C for 8 h were performed for ZK60 magnesium alloys modified with addition of 0.5, 1.5 and 2.5 wt% of mischmetal (combination of rare-earth (RE) elements). The compression behaviour was investigated at room temperature and at 300 °C correlated with the microstructure and differential scanning calorimetry (DSC) data. The as-cast microstructure is formed by a-Mg matrix with globular grains reinforced by a semi continuous network of Mg-Zn, Mg-Zn-RE and Mg-RE intermetallic particles. Solution-treated alloys show lower yield strengths due to partial dissolution of precipitates. Work hardening was not observed for the alloys compressed at 300°C with the compression speed of 10-3 s-1, whereas it was observed for the compression speed of 10-2 s-1 for the all as-cast, ZK60-1.5RE-T4 at 380 °C and ZK60-1.5RE-T4 at 380 °C.

We have developed a manufacturing system by combination of high-pressure synthesis method using a multi-anvil press, and spark plasma sintering (SPS) method. By means of the system, we have succeeded in synthesizing new filled skutterudite-type thermoelectric materials MmxCo4Sb12 (Mm=mischmetal). The thermoelectric properties of partially filled skutterudite compounds MmxCo4Sb12 synthesized under high pressure have been investigated. The Seebeck coefficient of MmxCo4Sb12 shows negative value, which means n-type conductivity. The highest dimensionless figure of merit ZT value is 0.25 for Mm0.6Co4Sb12 at 700 K.

A series of Al-rich Al-Mn-Ce alloys have been chill cast in copper molds and some were subjected to subsequent heat treatments. For all compositions studied, the ternary Al20Mn2Ce phase is formed as the primary phase surrounded by different constituents. The mechanical properties as a function of composition and heat treatment are presented and illustrate that this system is very versatile and that it is possible to tailor the compositions to produce alloys with high yield strengths, alloys with high hardnesses (for wear applications), and alloys with reasonably high ductilities. Alloys with high yield strengths and some ductility are obtained when the microstructure contains the ternary phase surrounded by the Al-Al11Ce3 eutectic constituent. Alloys with high hardnesses, can be obtained at higher Mn levels where the ternary phase and other intermetallics constitute most of the structure. Alloys with relatively high ductilities are possible at lower Ce and Mn levels where a metastable FCC solid solution of Mn in Al forms surrounding the ternary phase. Although the finely-distributed ternary phase is metastable, it appears to be relatively resistant to coarsening or decomposition. Finally, it is shown that Ce can be substituted by Mischmetal with no significant changes in either microstructure or properties. Keywords: Aluminum alloys, Al-Mn-Ce, Chill mold casting, High specific strength, Dispersion hardening, Electron microscopy

The effect of phosphorus on primary silicon, phosphorus and mischmetal (Ce-50La) modification on primary and eutectic silicon and cooling rate on microstructure of Al-25%Si are investigated. The results show that, with the addition of phosphorus, the size of primary silicon decreases from 93.6μm to 24.75μm. The morphology of primary silicon changes from irregular to polygonal. When Al-25%Si is modified by phosphorus and mischmetal, primary and eutectic silicon all change effectively. Addition of mischmetal on the basis of phosphorus modification have no influence to primary silicon, but it can make morphology of eutectic silicon change from lamellar to short rod-like when the content of mischmetal reaches 0.5%. The cooling rate curves show the change of temperature in different height of wedge-shaped mould. When cooling rate increases, microstructure of Al-25%Si refines, the size of primary silicon decrease to 22.7μm. The results obtained from mechanical testing demonstrate that the addition of mischmetal and increasing of cooling rate increase hardness value of Al-25%Si alloy.

Multiwalled carbon nanotubes have interesting electrochemical properties that can be utilized for the energy storage application. However, the practical application of multiwalled carbon nanotubes is limited by the current techniques to provide large scale production. So, the large scale production of multiwalled carbon nanotubes is obtained by catalytic chemical vapor deposition of acetylene/liquified petroleum gas on diatom supported Mischmetal based nickel alloy catalyst. The developed multiwalled carbon nanotubes are uniform in diameter and the method of production does not require any process of purification. The multiwalled carbon nanotubes along with the presence of diatom is used as the high capacity anode for the lithium-ion battery. The interaction of lithium ions with both multiwalled carbon nanotubes and diatom increases the specific capacity to 1090 mAh g−1 at 0.05 A g−1 with cyclic durability of 2000 cycles. This work demonstrates a scalable method for the production of multiwalled carbon nanotubes from a cost-effective catalyst with the benefit of utilizing it as a high capacity anode material for lithium-ion battery.

The microstructure and mechanical properties investigations of two AME503 and AME505 experimental alloys in as-cast conditions were presented. The investigated materials were fabricated on the basis of the AM50 commercial magnesium alloy with 3 and 5 wt.% cerium rich mischmetal. In the as-cast condition, both experimental alloys were mainly composed of α-Mg, Al11RE3 and Al10RE2Mn7 intermetallic phases. Additionally, due to non-equilibrium solidification conditions, a small amount of α + γ divorced eutectic and Al2RE intermetallic phase were revealed. The obtained results also show a significant influence of rare earth elements on Brinell hardness, tensile and compression properties at ambient temperature and especially on creep properties at 473 K. Improved alloy properties with a rise in rare earth elements mass fraction results from an increase in Al11RE3 phase volume fraction and suppression of α + γ eutectic volume fraction in the alloy microstructure. Additionally, the influence of rare earth elements on the dendrite arm space value was discussed. The presented results also proved the thermal stability of the intermetallic phases during creep testing.

Morphology evolution of eutectic Si in Ce-rich mischmetal (RE) modified Al-10wt.%Si alloy at different cooling rates was investigated. The morphology of eutectic Si and modification mechanism of RE was investigated by scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results showed that the RE modified eutectic Si exhibited a plate-like morphology under the low cooling rate (~100K/s). When cooling rate increased to ~600K/s, some branches were observed on the eutectic Si. In the RE modified alloy with a higher cooling rate (~1000K/s), the number of the branches on RE modified eutectic Si increased, and the morphology of eutectic S was modified to coral-like structure. The addition of Sr caused a flake-to-fiber modification of eutectic Si at low cooling rate, and the fiber size decreased with cooling rate increasing. The morphological observations indicated that the morphology of eutectic Si in RE modified alloy was significantly influenced by the cooling rate, while the modification efficiency of RE was lower than that of Sr.

Two duplex Mg–Li alloys, Mg–8.02Li–0.210Y and Mg–8.43Li–0.353Ymm (Y-rich mischmetal) alloys, were prepared by casting method with a permanent metal model. Microstructures, mechanical properties and deformation behaviors at tensile rates from 1.28 × 10−4 s−1 to 1.28 × 10−3 s−1 were evaluated. The results showed that when increasing the tensile speed, the strength increased with a decreasing elongation. The strength and ductility of Mg–8.02Li–0.210Y alloy were more sensitive to the tensile speed. Fracture occurred mainly in the β-Li phase, and the α-Mg phase participated into fracture at relatively high tensile speeds, which led to the strength increase of both alloys with the increment of tensile speed. Long-stripe-like α-Mg grains in Mg–8.02Li–0.210Y alloy hindered the fracture and resulted in a higher elongation. Mg–8.02Li–0.210Y alloy presented a serrated effect at a relatively high initial rate of 1.28 × 10−3 s−1. This was proposed to be resulted from the interaction between slips and α-Mg grains, which was quite different from the serrated effect explained by the dynamic strain aging (DSA) mechanism. Keywords: Mg–Li alloy, Dual phase, Tensile speed, Serrated effect, Slip

In this study, the wear and corrosion characteristics of six-pass friction stir processed (FSPed) AA1050/mischmetal oxide nanocomposite (6PPA) was compared to six-pass FSPed sample without powder (6 PA) and annealed base metal (BM). Different wear characteristics, such as weight loss, wear rate and coefficient of friction (COF) were studied. In order to evaluate the corrosion resistance of samples, immersion and cyclic polarization tests were performed. In addition, worn and corroded surfaces were investigated by field emission scanning electron microscopy (FESEM). The result of pin on disk dry sliding wear test revealed that wear resistance improved by employing FSP through finer grain structure (6 PA sample) and by incorporation of mischmetal oxides (MMOs) through lubrication and load-bearing action of particles (6PPA sample). At the constant load of 30 N, COF decreased from 0.9 to 0.85 and 0.75, and weight loss from 7.4 to 5.7 and 4.5 mg/m × 10−3 for the BM, 6 PA, and 6PPA samples, respectively. According to FESEM study of the worn surfaces, the BM and 6 PA samples show an adhesive wear mechanism, however the wear mechanism changed to abrasive for 6PPA sample. Based on immersion test results, corrosion rate of BM reduced from 0.41 to 0.36 and 0.29 mpy for the 6 PA and 6PPA samples, respectively. Moreover, the results of cyclic polarization test and FESEM investigation showed improved pitting resistance of 6PPA sample.

In order to prepare high-performance low-cost sintered (Nd, MM)-Fe-B magnets, the effect of the microstructure of strip-casting alloys on the particle size and distribution of powder was first investigated in this work. By adding lubricant and antioxidant to improve orientation and control oxygen content, the mischmetal-based sintered magnet possessing fine grains (~2.5 μm) along with smooth and continuous grain boundaries could maintain the excellent magnetic properties of Br = 12.31 kG, Hcj = 9.61 kOe and (BH)max = 36.52 MGOe by optimizing two-stage annealing temperature. The magnet prepared in this work exhibits record-high magnetic properties in the same proportion of MM substitution, which provides useful guidance for the preparation of MM doped magnets.

One of the prominent applications of magnesium alloys, thoroughly investigated in recent years, is medicine. The commercial WE43 (Mg-4wt.%Y-3wt.%mischmetal) alloy was reported to exhibit superior in vitro and in vivo performance, however, the presence and possible harmful effect of rare earth (RE) elements mischmetal in this alloy have been vastly debated. For this reason, the RE mischmetal was substituted in this study by pure neodymium, which exhibits rather low toxicity. In this way, a novel WN43 (Mg-4wt.%Y-3wt.%Nd) alloy was prepared, with well-defined composition. In order to attain a good control over the grain size and phase distribution, a modern spark plasma sintering (SPS) method was employed. The main objective of this study was to examine the effect of sintering parameters on the resulting microstructure (type and morphology of secondary phases, grain structure, and residual strain) and microhardness (Hv). The application of relatively high pressure (100 MPa) during consolidation leads to the production of practically fully compact final material. Increasing sintering temperature (from 400 up to 500 °C) stimulated homogenization and stabilization of the microstructure and reduction of the internal strain. On the other hand, the effect of sintering time (3 or 10 min) was rather negligible. Furthermore, the microhardness experiments revealed that the softening effect due to homogenization and decrease in the dislocation density at higher sintering temperatures was well-compensated by precipitation hardening as the hardness values were comparable in all the samples. The understanding of microstructure evolution as a function of sintering parameters can be of particular importance for subsequent mechanical, corrosion and in vivo degradation testing of this novel biomedical magnesium alloy.

The microstructure and mechanical properties of Mg–Zn-0.5Ca-0.5RE magnesium alloy, with zinc contents of 0, 2, 4, and 6 wt%, were studied. A significant effect of Ca and rare earth (RE) elements (via mischmetal addition) on the grain refinement of cast ingots was observed with the consequent enhancement of ultimate tensile strength (UTS). Moreover, while the grain size was refined by the addition of Zn, no significant α-Mg grain refinement occurred beyond 2 wt% Zn addition. The Mg12RE intermetallic compound was observed in all alloys while the Mg7Zn3 phase formed at the grain boundaries of Zn-containing alloys. Based on the competition of grain refinement as a favorable factor and formation of unfavorable grain boundary phases, the Mg–4Zn-0.5RE-0.5Ca (ZEX400) alloy showed the highest UTS among the cast alloys. Intense grain refinement introduced by the extrusion process and the fracturing and dispersion of the grain-boundary phases resulted in the significant enhancement of strength and ductility and the appearance of ductile fracture surface for the extruded Mg–4Zn-0.5RE-0.5Ca alloy. It was found that high Zn content (∼6 wt%) limits the usability and hot working temperature range of the alloys due to the problem of hot shortness and intergranular brittle fracture. Therefore, the addition of 4 wt% Zn was recommended for industrial practice. This work revealed the significant effects of alloying (with Ca, RE, and Zn) and hot extrusion process for microstructural refinement and enhancement of mechanical properties of Mg alloys.

Rare-earth (RE) mischmetal modification, homogenous annealing and rolling techniques were used to improve the microstructure and mechanical properties of an Al−1Fe alloy. Al 3 Fe, Al 6 Fe and Al 3 Ce intermetallic phases were found in the RE-modified alloys in the as-cast state. The RE modification refined the α-Al grains, resulting in a divorced eutectic and the formation of the Al−Fe phases in the forms of discontinuous networks, flakes and particles. Elemental La dissolved in the Al−Ce phases but did not dissolve in the Al−Fe phases. The dissolution of elemental Ce in the Al−Fe phase along with homogeneous annealing caused the claw-like Al−Fe phases to transform into short flakes and particles, which were uniformly distributed in the matrix by the rolling processes. A 0.3 wt% RE modification had the optimized effect on the microstructure and mechanical properties, while a 0.4 wt% RE addition resulted in the aggregation of the Al−Ce particles, which then deteriorated the mechanical properties of the alloys.

High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance. However, the influence of mischmetal (Ce-La) on the as-cast microstructures and mechanical properties of high speed steel has rarely been reported. Thus, the microstructure and mechanical properties of M2 high speed steel with addition of mischmetal (Ce-La) were investigated. The morphology and distribution of the eutectic carbides of the steel were observed by using optical microscopy and scanning electron microscopy, and the impact toughness and bending strength were tested. The results show that adding mischmetal has an obvious effect on the microstructure and mechanical properties of M2 high speed steel. The coarse eutectic structure is refined, the weak connection of the carbide networks is broken and the flake carbides become short and fine. More networks of eutectic carbides dissolve into the matrix. When a suitable adding content of mischmetal is selected, for example, 0.3 mass%, the impact strength and bending strength can increase by 27% and 10.76% compared with that without mischmetal, respectively.

Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available beta-Ni(OH)(2) and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the beta-Ni(OH)(2) electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to similar to 100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi(3.6)Al(0.4)Mn(0.3)Co(0.7), where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride gamma phase first and then to the beta phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.

The effect of calcium, manganese and cerium mischmetal additions on the mechanical properties of the extruded Mg-6Zn-1Y (wt%) alloy reinforced by quasicrystalline I-phase has been investigated. The tensile behaviour at room temperature can be rationalized on the basis of microstructural changes induced by the different elements added to the ternary alloy. The highest yield stress value corresponds to the material modified with cerium-rich mischmetal. Manganese addition leads to the best balance between strength and ductility while calcium addition has a negligible effect on the mechanical properties of ternary alloy. The analysis of the contributions of the different strengthening mechanisms operating during deformation reveals that grain size refinement is the main hardening contribution in all alloys mechanism followed by the strengthening due to coarse second phases. The hardening due to basal texture conferred by the existence of coarse non-recrystallized grains depends on the overall hardening induced by the rest of strengthening mechanisms., The authors are grateful to the Spanish Ministry of Economy and Competitiveness for financial support for this work under project number MAT2012-34135. We would like to acknowledge the expert support of A. García and A. Tomás for assistance with SEM.

In the present work, fcc-Al nanoparticle development in Al 90− x Ni 10 MM x (MM: Ce mischmetal; x =2, 4) amorphous alloys was studied via non-isothermal differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and nanoindentation test. Results showed that the crystallization of Al 88 Ni 10 MM 2 alloy occurred by the precipitation of fcc-Al nanoparticles followed by the crystallization of Al 11 MM 3 and Al 3 Ni phases. Transmission electron microscopy revealed that the aluminum precipitates had an average size of ~12 nm with a round morphology. Increasing the mischmetal content to 4 at% (Al 86 Ni 10 MM 4 alloy) caused a three-stage crystallization process with a change in the size and morphology of fcc-Al precipitates. Here, fcc-Al nanoparticles got an irregular and cluster-like morphology with an average size of about 50 nm. The crystallization mechanism of fcc-Al nanoparticles formation was evaluated. The results indicated the complex nature of the primary crystallization behavior of these amorphous alloys. Results of nanoindentation test revealed that controlled crystallization of the amorphous alloys significantly increased the strength, owing to the solute enrichment of the amorphous matrix.

The hot deformation behavior of as-cast AISI M2 high-speed steel containing mischmetal (RE) has been investigated on a Gleeble-3500 simulator in the temperature range of 1000—1150 °C and strain rate range of 0. 01 – 10 s−1 at true strain of 1. 0. The mechanical behavior has been characterized using stress-strain curve analysis, kinetic analysis, processing maps, etc. Metallographic investigation was performed to evaluate the mechanism of flow instability. The results show that the deformation activation energy decreases with increasing deformation temperature; the efficiency of power dissipation increases with decreasing strain rate and increasing temperature; flow instability is observed at low-to-medium temperature and higher strain rate region when the strain is smaller, but extends to lower strain rate and high temperature regions with the increment of strain, in which it is manifested as flow localization near the grain boundary. Hot deformation equations and processing maps are obtained. The optimal processing window is suggested and the deformation mechanism is dynamic recrystallization (DRX).

The present investigation is aimed to study MmNi5-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm0·8La0·2Ni3·7Al0·38Co0·3Mn0·6−x Mo0·02Fe x (x = 0, 0·1, 0·2 and 0·3). The alloys are synthesized by radio-frequency induction melting. To study their electrochemical properties via measurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg−1 for the iron concentration, x = 0·1, as compared to 270 mAhg−1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode (x = 0·1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution (x = 0·1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.

Totalized Hydrogen Energy Utilization System (THEUS), which consists of fuel cells, water electrolyzers, hydrogen storage and their auxiliary components, is proposed for the stationary application. In the previous researches, mischmetal-based MmNi 5 compound was used for the stationary hydrogen storage in THEUS. However, the cost of mischmetal is so expensive that can be an obstacle to the practical use of THEUS. In addition, since THEUS utilizes hydrogen produced by water electrolysis, it is necessary to confirm the influence of the water contamination on the metal hydride reactivity. The samples were Ti 0.24 Zr 0.76 Ni 1.2 Mn 0.64 V 0.14 Fe 0.18 (Sample A) and the sample with 1 at.%-La addition (Sample B). Using hydrogen including 40 ppm-water, hydrogen absorption and desorption was carried out 30 times. The degradation of hydrogen storage capacity was observed for Sample A while not observed for La-added Sample B. The results revealed that the addition of La improved cyclic stability against the water contamination.

An extensive study was carried out to investigate the types of intermetallic phases observed in non-modified and Sr modified A319?1, A356?2 and A413?1 alloys with 0, 2, 4 and 6 wt-% mischmetal (MM) additions and solidified under high and low cooling rate conditions. Quantification of the intermetallics was carried out using electron probe microanalysis and revealed that the total surface fraction of intermetallic phases increased with the addition of MM to the alloys. Wavelength dispersion spectroscopic analysis was employed to identify these phases. In addition to the Al2Cu phase in A319?1 alloy, the Mg2Si phase in A356?2 alloy and the plateletlike b-Al5FeSi and a-Al15(MnFe)3Si2 and a-Al15(MnFeNiCu)3Si2 Chinese script-like iron intermetallic phases in the A413?1 alloy, various MM containing intermetallic phases were observed at high and low cooling rates, each exhibiting a specific Ce/La ratio and morphology. Many of these MM containing intermetallic phases were found to contain Sr, which confirmed the interaction of MM with Sr. Thus, the effectiveness of Sr as a modifier of the eutectic Si phase in these alloys would be reduced.

As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloyson the steel cleanness. Thus, the number, morphology, size and composition of inclusions in sixdifferent ferroalloys (FeTi, FeNb, FeSi,SiMn, LC and HC FeCr) were investigatedin this study. This was done in three dimensions (3D) by using a SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Theresults show that thenon-metallic and metallic inclusions can besuccessfully analyzed on the surface of a film filterafter a separation of the inclusions from the matrix. Overall, the inclusions canbe divided into two categories depending on the melting point. Furthermore, the possible transformation of different kinds of inclusions after their addition to the liquid steel canalso be determined.The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were also investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: a low Al steel (LAl) and a high Al steel (HAl). Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It wasfound that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a low Al steel are MgO-CaO-SiO2-Al2O3spherical inclusions. The compositions of irregular and regularinclusions and clusters in steel samples of a high Al steel were mostly MgO·Al2O3spinel, but also complex sphericalinclusions containing Al2O3-MgO-CaO-SiO2. In addition, the phase stabilitydiagram based on Darken’s quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. Therefore, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at differentholding times after the addition of a mischmetal. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of the holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples.Largesize inclusions are recognized to be crucially harmful for the mechanical properties of steel products. Therefore, predictionsof the maximum size of Al2O3-CaO spherical inclusions in an Fe-10 mass% Ni alloy have been examined based on two dimensional (2D) and three dimensional (3D) investigations. The effects of the number of measurements and unit volume on the estimated 3D results were also investigated.

The phase structures, surface morphologies and electrochemical kinetic properties of MmNi4.50−xMnxCo0.45Al0.30 (Mm is the mischmetal, x = 0.25, 0.30, 0.35, 0.40 and 0.45) hydrogen storage alloys have been investigated in this paper. The X-ray diffraction (XRD) shows that all the alloys mainly consist of LaNi5 phase with CaCu5-type structure, which belongs to P6/mmm space group (central symmetry). Scanning electron microscopy (SEM) tests indicate that there are partial element segregations in the alloys. Meanwhile, energy dispersive spectrum (EDS) results display that the elements constituting Mm exist in the matrix phase in relatively larger proportion, while Mn, Al and Co tend to appear in precipitate phase. For the alloy with x = 0.35, the electrochemical performances, including discharge capacity, high-rate dischargeability (HRD) and cycling life, of the alloy electrode are better than that of other alloy electrodes. With the increase of Mn content, the exchange current density (I0) of the alloy electrodes first increases and then decreases, the hydrogen diffusion coefficient (D) of alloy electrodes gradually decreases. There is a linear correlation between HRD at a discharge current density of 1500 mA/g and I0.

Conventional magnesium alloy Mg–1Zn–0.4Zr and a modified version of the same alloy containing Nd-based rare earth mischmetal and Y were extruded at 400 °C to study dynamic recrystallization and its role in the microstructure and texture development. Second phase particles in the modified alloy seemed to generate new orientations other than the deformed orientation. Although this occurred within small volume fraction of the material, the respective recrystallizing grains grew up to considerable sizes consuming larger volumes of the extruded microstructure and dominating the bulk texture. The consequent mechanical behavior tested in plane strain compression at room temperature demonstrated improved strain hardening behavior and enhanced ambient formability relative to the conventional alloy due to well-scattered texture and prolonged activity of basal slip within a large volume of the deformed microstructure.

The effects of calcium, manganese and cerium-rich mischmetal additions on the microstructure and texture of the extruded Mg-6Zn-1Y (wt. %) alloy have been investigated. The microstructure of the alloys consisted of a magnesium matrix embedding second phase particles aligned along the extrusion direction. The nature and volume fraction of the second phases depended on the alloying element. Thus, Ce-rich mischmetal promoted the formation of T-phase while calcium additions resulted in the formation of a ternary Mg-Zn-Ca compound. Only, manganese additions did not affect the existence of the I-phase present in the ternary alloy. The texture was measured and it was found that calcium addition has a significant effect weakening the extrusion texture., We would like to acknowledge financial support of the Spanish Ministry of Economy and Competitiveness under project number MAT2012-34135. We would like to acknowledge the expert support of A. García and A. Tomás for assistance with TEM and SEM. We also would like to acknowledge the support of M. Acedo and Dr. F.A. López for assistance with the extrusion processing and conventional DSC experiments, respectively. The Deutches Elektronen-Synchrotron DESY is acknowledged for the provision of beamtime at the P07 beamline of the Petra III synchrotron facility in the framework of proposal I-20140198 EC.

The influences of Y and Y-rich mischmetal (Ym) additions on microstructural and compressive properties of as-cast Al-13Mg-0.8Mn alloy prepared by vacuum suction casting were investigated in this study. The average secondary dendrite arm spacing (SDAS) was decreased when adding Y and Ym additions. Moreover, the Al2Y and Al2Ym phases formed during the solidification were mainly distributed along the grain boundary. The mechanical results reveal that both Y and Ym additions are effective in increasing the compressive strength and hardness. The values of yield compressive strength, ultimate compressive strength, and Brinell hardness of the as-cast Al-13Mg-0.8Mn-0.8Y alloy are 357 MPa, 510 MPa, and 138, respectively. The improved mechanical properties are mainly attributed to fine SDAS and precipitation strengthening. A typical cleavage fracture mode is observed on the compressive fracture surfaces of the alloys.

The effects of La-based mischmetal (MM) and heat treatment on the microstructure and tensile properties of two different sections of A357 Al–Si casting alloy have been investigated in this study. Different concentrations (0–1 wt%) of the MM were added to the molten alloy directly. The tensile testing was employed to measure the quality index (Q.I.=UTS+150×log (elongation)) for evaluating the modification efficiency of the alloy with different MM contents. T6 heat treatment was applied before tensile testing. The results showed that the optimum levels of added mischmetal are 0.1 wt% and 0.3 wt% for thin and thick section castings respectively. A new AlSiLa intermetallic was detected through the microstructural studies at higher MM levels. Further results demonstrated that T6 heat treatment improves tensile properties of the modified alloy significantly. The differences observed in the fracture behavior were attributed to the microstructural changes as well as morphological aspects of Si particles.

The microstructure difference and enthalpy changes have been investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) during the as-cast ageing process. After the as-cast ageing process, the eutectic silicon and α-Al is in the ideal state for the alloy with 0.08 wt% mischmetal (MM) addition. The energy of the phase transformations is 5.8 J/g during the isothermal process, when Al-11%Si-0.27%Mg alloy is aged at 150°C. When the additive contents of MM are 0.03, 0.06, 0.08 and 0.1 wt%, respectively, the energies of phase transformations are 4.98, 1.39, 1.07 and 1.25 J/g correspondingly. It is shown that the energies of phase transformations decrease gradually as the MM content increases from 0 wt% to 0.08 wt%; the energies then increase upon further addition of the MM concentration from 0.08 wt% to 0.1 wt% in the as-cast ageing process. Furthermore, the beginning time of phase transformations is delayed with the MM addition.

The current study examines the influence of select rare earth elements; Gd, Nd, Ce, La and mischmetal (MM) on the sheet texture modification during warm rolling and annealing of a ZEK100 magnesium alloy, and the resulting formability and anisotropy during subsequent tensile testing at room temperature. It was found that all the investigated RE elements led to weak sheet textures and hence promoted enhanced ductility and reduced anisotropy over conventional Mg sheet. Gd was of a particular interest because it gave rise to a desired Mg sheet texture despite its coarsest grain size resulting in promising mechanical properties. It is suggested that solute related effects on the grain boundary migration and the relative strengths of different deformation mechanisms are responsible for altering the common concepts of recrystallization and grain growth during annealing, and the activation scenarios of slip and twinning during deformation.

The influence of 0.1–1.0 wt% mischmetal (MM) additives on the microstructures, tensile properties, and fracture behavior of A356 alloys were investigated in detail under the as-cast condition. Experimental results show that, after introducing a small amount of MM, grain coarsening occurred, the eutectic silicon was well modified, and RE-containing intermetallic compounds containing Al, Si, Mg, La, and Ce elements were formed. The size, shape, and distribution of RE-containing compounds are also studied. Tensile tests revealed that MM addition decreases the tensile strength and ductility of the materials. The fracture path goes through the interdendritic regions containing eutectic silicon and RE-containing compounds.