Al For Cu Research Articles

Glass-Forming Ability, Mechanical Properties, and Energetic Characteristics of ZrCuNiAlNbHfY Bulk Metallic Glasses.

The effects of partially substituting Al for Cu in Zr59.62Cu18.4-xNi12Al6+xNb3Hf0.78Y0.2 (x = 0, 2, 4, 6, 8 at.%) bulk metallic glasses (BMGs) on their glass-forming ability (GFA), quasi-static and dynamic mechanical properties, and energy characteristics were investigated. The results showed that an appropriate substitution of Al for Cu can improve GFA and reach a critical casting size up to 10 mm. Additionally, with Al replacement of Cu, the change in the distribution and content of free volume inside the BMGs was the main reason for the quasi-static compression plasticity. In contrast, the BMGs exhibited no plasticity during dynamic compression and high-speed impact, owing to the short loading time and thermal softening effect. In terms of energy characteristics, all alloys have a high combustion enthalpy. And on the surface of the fragments collected from impact, the active elements Zr, Al, and Nb reacted because of the adiabatic temperature rise. Further, x = 4 at.% Zr-based BMG with its superior overall performance could penetrate a 6 mm Q235 plate at a speed of 1038 m/s, combining excellent mechanical properties and energy characteristics. This study contributes to the development of Zr-based BMGs as novel energetic structural materials.

Effect of Al/Cu on the magnetic properties and microstructure of Nd-Fe-B sintered magnet by diffusing Pr-Tb-(Cu, Al) alloys

Grain boundary diffusion process (GBDP) using Pr60Tb10Cu30−xAlx (x = 0, 5, 15, 25, 30, atomic fraction) alloy ribbons, named as A0–A30 alloys, was applied to high maximum energy product (BH)max Nd-Fe-B sintered magnet. After diffusion, coercivity (Hci) of A0 magnet is significantly enhanced from the original 11.4 kOe to 19.5 kOe with remanence (Br) decreasing from 14.65 kGs to14.32 kGs, which is mainly attributed to magnetic hardening effect by Tb-rich shells. With substituting 5 at% Al for Cu, the Hci and Br of A5 magnet are simultaneously enhanced by the homogenized distribution of Tb-rich shells and the reduced interface energy of Nd-rich phase and Nd2Fe14B phase. The highest coercivity of 22.4 kOe is obtained for A25 magnet by further strengthening magnetic isolation of Nd2Fe14B phase, however, which results in a drastic decrease in Br due to the increased fraction of Nd-rich phase and too much substitution of Al for Fe in Nd2Fe14B phase. Therefore, the Hci (kOe) + (BH)max (MGOe) reaches to the peak value for A5 magnet. Also, it is proven that Cu/Al co-addition can effectively improve Tb diffusion efficiency by modifying intergranular Nd-rich phase.

Use of Paleoflood Deposits to Determine the Contribution of Anthropogenic Trace Metals to Alluvial Sediments in the Hyperarid Rio Loa Basin, Chile

Toxic trace metals are a common and significant contaminant in riverine ecosystems, and are derived from both natural and anthropogenic sources. Determining the contributions of metals from these sources has proven difficult, in part, because physical and biogeochemical processes alter the nature (e.g., grain size, mineral composition, organic matter content) of the source materials as they are transported through the drainage network. This study examined the use of paleoflood deposits located along the hyperarid Rio Salado, a tributary to the Rio Loa of northern Chile, to construct local background functions and enrichment factors (LEFs) to differentiate between natural and anthropogenic metal sources. Significant variations in metal content occurred between river reaches and flood deposits of a given reach; these variations were primarily related to changes in sediment source that may reflect differences in El Niño and La Niña precipitation patterns. Three conservative elements (Al, Fe, Co) were examined to construct background functions for seven trace metals. Cobalt yielded the most effective background functions for As, Cd, Ni, Pb, and Zn; Fe was selected for Cr, and Al for Cu. The resulting LEFs approximated 1, illustrating that paleoflood deposits produced effective background functions, and could be applied to downstream sites contaminated by mining activity.

島根県銅ヶ丸鉱山および滋賀県御池鉱山産ハイドロウッドワード石の化学組成

Four hydrowoodwardite samples, simplified formula [Cu1−xAlx(OH)2](SO4)x/2•mH2O (0.03≦x≦0.38)], collected from the Dogamaru mine, Shimane Prefecture and the Oike mine, Shiga Prefecture were characterized by powder X-ray diffraction, Fourier transform infrared (FT-IR) and electron microprobe analyses. The samples obtained from the Dogamaru and Oike mines occur as green to blue colloidal crusts (0.5 mm to 20 mm in thickness). The samples indicate fine bedded texture (1 μm to 10 μm in thickness) corresponding to the different compositions. Powder X-ray diffraction patterns are close to those of hydrowoodwardite. FT-IR spectra showed absorption bands at around 3450 cm−1 due to O-H stretching vibration, at around 1640 cm−1 due to H-O-H bending vibration, at around 1100 cm−1 due to v3 and v1 SO42− stretching vibrations, and at around 620 cm−1 and 470 cm−1 due to v4 and v2 SO42− bending vibrations, respectively. Weak absorption bands at around 1395 cm−1 due to carbonate group are observed in the Dogamaru samples. Electron microprobe analyses revealed that the main components are Cu, Al, S, and Si; Si is derived from amorphous silica. Small amount of Zn is contained in the Dogamaru samples. The predominant mechanism for changes in chemical composition of the each sample is substitution of Al for Cu with constant Zn ratios. The ranges of Cu, Zn, Al, and S (apfu) in the Dogamaru and Oike samples are as follows: Cu 0.53–0.89 and 0.62–0.96; Zn 0.03–0.17 and 0.00–0.01; Al 0.04–0.38 and 0.03–0.38; and S 0.02–0.16 and 0.02–0.17, respectively. The minimum values of Al are smaller than any of previously reported hydrowoodwardite.

Effect of component substitution on the microstructure and mechanical properties of MCoCrFeNiTi x (M = Cu, Al) solid-solution alloys

MCoCrFeNiTix (M = Cu, Al; x: molar ratio, x = 0, 0.5) alloys were prepared using the new alloy-design strategy of equal-atomic ratio and high entropy. By the component substitution of Al for Cu, the microstructure changes from the face-centered cubic solid solution of original CuCoCrFeNiTix alloys to the body-centered cubic solid solution of AlCoCrFeNiTix alloys. Compared with original CuCoCrFeNiTix alloys, AlCoCrFeNiTix alloys keep the similar good ductility and simultaneously possess a much higher compressive strength, which are even supe-rior to most of the reported high-strength alloys like bulk metallic glasses.

Effect of Al addition on formation and mechanical properties of Mg-Cu-Gd bulk metallic glass

The effect of partial substitution of Al for Cu on the glass forming ability(GFA) and mechanical properties of Mg 65Cu 25- x Al x Gd 10 ( x=0, 1, 3 and 5, molar fraction, %) alloys were studied by X-ray diffractometry(XRD), differential scanning calorimetry(DSC) and uniaxial compression test. The result reveals that GFA of the alloys changes slightly with increasing x from 0 to 3, and then abruptly decreases with x increasing up to 5. The plasticity can be greatly improved with appropriate substitution of Cu by Al (3%, molar fraction) in Mg 65Cu 25Gd 10 bulk metallic glass, and the resultant fracture strength, total strain to failure, and plastic strain are 898 MPa, 2.19% and 0.2%, respectively.

Determination of the 76 wt.% Au section of the Al–Au–Cu phase diagram

The substitution of Al for Cu along the 76 wt.% Au section of the Al–Au–Cu system causes the α phase of the Au–Cu edge to be successively replaced by a ternary β electron compound, a ternary extension of the Cu–Al γ electron compound, designated here as γ′, and finally the compound AuAl 2. A vertical section of this part of the phase diagram has been determined and is presented here, and the relationships between the phases explored. It is considered likely that the section contains the peritectic reactions L+α→β and L+γ′→β. Both the α and the β phases form ordered phases at lower temperatures.

Mechanically Alloyed Amorphous Ti50(Cu0.45Ni0.55)44–xAlxSi4B2 Alloys with Supercooled Liquid Region

A high-energy ball milling procedure has been developed to produce amorphous alloys in Ti50(Cu0.45Ni0.55)44−xAlxSi4B2 (x= 0, 4, 8, 12) powder mixtures. The milling products were characterized using x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The Ti-based amorphous alloy powders prepared through this solid-state process exhibit a well-defined glass transition and a supercooled liquid region (ΔTx =64 K) close to the largest achieved so far for Ti-based undercooled melts. The substitution of Al for Cu and Ni has beneficial effects on stabilizing the supercooled liquid. Residual nanocrystals of the αTi structure are uniformly dispersed in the amorphous matrix. The composite alloy powders offer the potential for consolidation in the supercooled liquid region to bulk lightweight amorphous alloys and the possibility to attain desirable mechanical properties.

Magnetic and electrical properties of the pseudo-binary GdCu 5− xAl x compounds

The effect of substitution of Al for Cu on the lattice parameters, and the magnetic and electrical properties of the GdCu 5− x Al x compounds has been studied. The behaviour of the compounds with low Al concentration (0≤ x≤0.5) differs markedly from that of the compounds with high Al concentration (1.0≤ x≤1.5): for x≤0.5 the compounds appear to have a complex magnetic structure, whereas for the higher Al concentration a standard two-sublattice model yields values for the intra- and intersublattice coupling parameters. For x≤0.5, below the ordering temperature, the magnetic component of the electrical resistivity decreases with increasing temperature, whereas for the higher Al concentration this component increases. These electrical properties are analysed in terms of a change in the band gap with increasing Al concentration, taking into account spin fluctuation terms.

Antiferromagnetic instability of heavy-fermion alloys with conduction band impurities

The antiferromagnetic instability of heavy-fermion alloys with conduction band impurities is examined in the single-site coherent-potential approximation with the strong correlation treated by the slave-boson technique of Kotliar and Ruckenstein. The variation of the paramagnetic-antiferromagnetic phase boundary with the impurity concentration is studied in the case of isoelectronic doping. Our results show that the isoelectronic doping favours the formation of antiferromagnetism if the impurities increase the cell volume, thus suppressing the c-f mixing, which is in agreement with experimental observations in Ce(Cu1-xAgx)6 and Ce(Cu1-xAux)6. The obtained phase diagram can also be used to explain the effect of nonisoelectronic substitutions of Al for Cu in CeCu6.

On the superconductivity suppression in the oxide systems Y 1−x Pr x Ba2Cu3−y M yOz (M = Zn and Al)

Superconductivity suppression induced by Pr ions in the YBa 2Cu 3O 7 system has been investigated by using co-substitution of Pr for Y along with Zn and Al for Cu. It is observed that the behaviour of T c in the Y 1−xPr xBa 2 Cu 3−y Zn y O z system is different from that in the Y 1−xPr x Ba 2Cu 3− yAl y O z system. The rate of T c suppression with respect to the Pr concentration, x, which is described by -(d T c/d x) | y , increases with an increase of the Zn content, but decreases with increasing the Al content. Possible explanations are given.

Charge-transfer and compression effects of isomorphous substitutions in YBa2Cu3O7.

The influence of partial isomorphous substitutions at the Cu and Ba sites of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ on the phonon spectrum and the structure has been investigated systematically by Raman scattering and neutron diffraction. For partial substitution of Sr for Ba the vibrational frequency of the apex oxygen, O(4), increases as expected from the observed compression of the structure in the region between the ${\mathrm{CuO}}_{2}$ planes and the CuO chains. Substitutions of trivalent ions such as Co, Fe, and Al for Cu change the coordination of the apex oxygen in a way consistent with an elimination of holes in the ${\mathrm{CuO}}_{2}$ planes. The O(4) vibrational frequency decreases rapidly with increasing trivalent substitution. The changes cannot be explained in a simple way by the bond-length changes observed in the neutron-diffraction experiments. A remarkable correlation is found between ${\mathit{T}}_{\mathit{c}}$ and the O(4) Raman mode for trivalent substitutions on the Cu(1) site and for oxygen deficiency. We suggest that this correlation as well as the rapid decrease of ${\mathit{T}}_{\mathit{c}}$ and the structural changes we observe are caused by a hole charge transfer from the ${\mathrm{CuO}}_{2}$ planes to the CuO chains.

Twin to tweed transition in YBa 2Cu 3O 7–δ by substitution of Al for Cu

The substitution for Cu by Al in YBa 2(Cu 1− x Al x ) 3O 7− δ has been studied by means of high voltage electron microscopy (HVEM). The higher oxygen coordination of the impurity ions in the chain plane leads to a twin refinement for weakly doped samples ( x⩽0.03) and to the formation of microdomains at higher concentrations of the impurity. A displacement wave which provides a reduction of the strain energy of the distortion between the microdomains forms the tweed structure. The analysis of the diffraction streaks of tweed by in-situ-heating shows that the wavelength of the modulation increases if the oxygen concentration decreases.

Effect of chemical substitution on superconductivity in YBa 2Cu 3O 7− z, Bi 2Sr 2YCu 2O 8+ z, and Bi 2Sr 2CaCu 2O 8+ z

Chemical substitution on different sites in superconducting phases affects the layer spacing and electric charge distribution along the c -axes and hence the charge carrier density in the Cu O 2 planes. Alkali element doping in Bi 2 Sr 2 CaCu 2 O 8+ z (BSCCO) and Bi 2 Sr 2 YCu 2 O 8+ z (BSYCO) raises the T c while co-doping of Ca for Y and Al for Cu(1) in YBa 2 Cu 3 O 7− z (YBCO) leads to a gradual depression in the T c due to counterbalancing effects of Ca and Al doping.

Effect of co-doping of Ca and Al on hole concentration and superconductivity in the YBa 2Cu 3O 7−y system

The effect of co-substitution of Ca for Y and Al for Cu(1) in the Y 1− x Ca x Ba 2Cu 3− x Al x O 7− y has been investigated in comparison with the individually doped systems Y 1− x Ca x Ba 2Cu 3O 7− y and YBa 2Cu 3− x Al x O 7− y . Substitution of Ca for Y reduces the positive charge in the CuO 2YCuO 2 layer so that the internal electric field along the c-axis tends to transfer holes from the chains to the sheets. On the other hand, substitution of Al for Cu(1) increases the oxygen content in the CuO chains resulting in hole transfer from the sheets of chains. In the co-doped system the delocalisation effect of Ca-doping on holes countervails the localisation effect of Al-doping, leading to a slow variation in the mobile hole concentration, and hence a very slow drop in the T c. The orthorhombic to tetragonal structural transition in this co-doping system is influenced only by Al substitution for Cu(1), and is not affected by Ca doping.