Academic literature on the topic 'Al-Cu-Hf-Zr'

This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Feand Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials.

This research work dealt with production of amorphous powder with nominal composition of (Cu55Zr45Al10)97Hf3 (at%). Combining the mechanical milling and alloying, powder of crystalline Cu-Zr-Al alloy mixed with Hf elemental powder were milled in order to produce a homogenous and amorphous alloy powder The master alloy and the powders milled for different time were analyzed by X-Ray Analysis (XRD) and Scanning Electron Microscopy (SEM). Particle size distribution and hardness were controlled during milling and at the end of procedure. The milling caused dissolving of the hafnium. The 25 h milling time was the optimal to obtain the Hf containing powder with amorphous structure. However, elemental Hf traces with size below 3 µm were still observed in the powder. After 50 h of milling, such impurity elements as iron, nickel, chromium originating from milling tools (vial, balls) were detected.

The transformation behavior from glassy state was investigated in Zr- and Hf-based glassy alloys. The primary phases are metastable face-centered-cubic (fcc) Zr2Ni and fcc Hf2Ni phases in the Zr65Al7.5Ni10Cu17.5 and Hf65Al7.5Ni10Cu17.5 glassy alloys, respectively. By substitution of 5 at.% Pd for Cu, the primary phase changes to an icosahedral quasicrystalline phase in both alloys. It is found that the addition of elements, which have a positive or weak chemical affinity with one of the constitutional elements in the Zr–Al–Ni–Cu and Hf–Al–Ni–Cu glassy alloys, is effective for the precipitation of the icosahedral phase. It is suggested that Pd plays a dominant role in an increase in the number of nucleation sites. Since an icosahedron is contained as a structure unit in the icosahedral, fcc Zr2Ni and fcc Hf2Ni phases, it is implied that these phases are correlated with the local icosahedral order. The high-resolution transmission electron microscopy images of the as-spun Zr65Al7.5Ni10Cu7.5Pd10 and Hf65Al7.5Ni10Cu12.5Pd5 alloys reveal a possibility of the existence of the icosahedral ordered regions. It is therefore, concluded that the icosahedral short- or medium-range order exists and it stabilizes the glassy state in the Zr- and Hf-based multicomponent alloys.

Thermal stability of composite bimetallic wires from five novel microalloyed aluminum alloys with different contents of alloying elements (Zr, Sc, and Hf) is investigated. The alloy workpieces were obtained by induction-casting in a vacuum, preliminary severe plastic deformation, and annealing providing the formation of a uniform microstructure and the nucleation of stabilizing intermetallide Al3(Zr,Sc,Hf) nanoparticles. The wires of 0.26 mm in diameter were obtained by simultaneous deformation of the Al alloy with Cu shell. The bimetallic wires demonstrated high strength and improved thermal stability. After annealing at 450–500 °C, a uniform fine-grained microstructure formed in the wire (the mean grain sizes in the annealed Al wires are 3–5 μm). An increased hardness and strength due to nucleation of the Al3(Sc,Hf) particles was observed. A diffusion of Cu from the shell into the surface layers of the Al wire was observed when heating up to 400–450 °C. The Cu diffusion depth into the annealed Al wire surfaces reached 30–40 μm. The maximum elongation to failure of the wires (20–30%) was achieved after annealing at 350 °C. The maximum values of microhardness (Hv = 500–520 MPa) and of ultimate strength (σb = 195–235 MPa) after annealing at 500 °C were observed for the wires made from the Al alloys alloyed with 0.05–0.1% Sc.

Transition metal trialuminides of the Al3X type of groups 4 and 5 of the periodic system have reduced density, high melting points, and corrosion resistance. Aluminides with a cubic lattice of the Al3Sc type can be used as a nucleating phase for aluminum alloys. However, low plasticity and a tetragonal lattice limit their application. In this work, we stabilized the metastable cubic lattice of Al3X-type aluminides by replacing aluminum with copper. The conditions for the formation of L12 metastable aluminides in the Al‒Cu‒TM (TM: Ti, Zr, Hf) alloys were studied using a wide range of copper concentrations. A high concentration of copper (hypereutectic alloys) is the one of the necessary conditions for the formation of (Al1−хCuх)3Ti, (Al1−хCuх)3Zr, (Al1−хCuх)3Hf aluminides. With an increase in the copper concentration, the number of metastable aluminides sharply increased. The process of their formation strongly depended on the sequence of dissolution of the corresponding components in the melts. The low volume fraction of precipitated titanium aluminides was the result of insufficient supersaturation of α-Al with titanium (at the peritectic temperature) compared to that for alloys with zirconium and hafnium. Under identical synthesis conditions in the crystal lattice of metastable aluminides formed in experimental Al–Cu–Ti, Al–Cu–Zr, Al–Cu–Hf alloys, copper was found to substitute up to 8, 10, and 13 at.% of aluminum, respectively. The crystallographic and dimensional similarities of the lattices in metastable transition metal aluminides and in α-Al suggest their usefulness as modifying additions in aluminum-based alloys.

A systematic study of the stacking fault energy (?SF) for the dilute Al-based alloys (Al23X, Al47X and Al71X, where X = Al, Ag, Be, Ca, Cd, Co, Cu, Cr, Fe, Ga, Ge, Hf, In, K, La, Li, Mn, Mg, Ni, Na, Pb, Sc, Sn, Sr, Si, Ti, V, Zn, and Zr) has been performed by means of first-principles calculations. Alias shear deformation is adopted in the present investigations. The presently calculated ?SF for Al is in favorable accordance with experimental and other theoretical data. For the targeted elements, the calculations indicate that Na, Si, K, Ca, Sc, Ga, Ge, Sr, Zr, In, Sn, La, Hf, and Pb, in any concentration we considered, decrease the ?SF of Al, while Ag, Be, Cd, Co, Cu, Cr, Fe, Li, Mn, Mg, Ni, Ti, V, and Zn increase the ?SF of Al, when the concentration of alloying elements is 1.39 at. % in the system. With increasing concentration of alloying elements, Li, Mg, V, Ti, and Cd change from increasing the ?SF of Al to decreasing it, based on present investigations. Among the alloying elements, which decrease the ?SF of Al, La decreases the ?SF most significantly. It is also found that the ?SF of Al-X generally decreases with the increase of equilibrium volume. The results obtained in the present work provide an insight into the design of Al based alloys.

Magnetron sputtering and DFT calculations revealed that the single-doped Cu-MoS₂, Au-MoS₂, Ag-MoS₂, and Al-MoS₂ exhibited distinct phase transitions compared to Cr-MoS₂, Hf-MoS₂, Ta-MoS₂, and Zr-MoS₂, due to the introduction of additional charge.

AbstractZircon from 14 representative granite samples of the late-Variscan Cornubian Batholith in SW England was analysed for W, P, As, Nb, Ta, Si, Ti, Zr, Hf, Th, U, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Al, Sc, Bi, Mn, Fe, Ca, Pb, Cu, S and F using electron probe microanalyses. Zircons from the biotite and tourmaline granites are poor in minor and trace elements, usually containing 1.0–1.5 wt.% HfO2, <0.5 wt.% UO2 and P2O5, <0.25 wt.% Y2O3, <0.2 wt.% Sc2O3 and Bi2O3 and <0.1 wt.% ThO2. Zircon from topaz granites from the St. Austell Pluton, Meldon Aplite and Megiliggar Rocks are slightly enriched in Hf (up to 4 wt.% HfO2), U (1– 3.5 wt.% UO2) and Sc (0.5–1 wt.% Sc2O3). Scarce metamictized zircon grains are somewhat enriched in Al, Ca, Fe and Mn. The decrease of the zircon Zr/Hf ratio, a reliable magma fractionation index, from 110–60 in the biotite granites to 30–10 in the most evolved topaz granites (Meldon Aplite and Megiliggar Rocks), supports a comagmatic origin of the biotite and topaz granites via long-lasting fractionation of common peraluminous crustal magma. In comparison with other European rare-metal provinces, the overall contents of trace elements in Cornubian zircons are low and the Zr/Hf and U/Th ratios show lower degrees of fractionation of the parental melt.

The present work aims at developing a new class of high temperature alloys based on ordered intermetallic compound that forms coherently with the matrix during solid state transformation. The chosen intermetallics have L12 ordered structure, which is a derivative of fcc unit cell. Most popular example of this fcc derivative is Ni3Al that is critical in developing high strength at high temperatures (~900°C) in commercially successful Ni based superalloys. Similar ordered structures form either in stable or metastable form can act as a main strengthening constituent in Al and Co matrices. For example Al3Sc, Al3Zr, Al3Hf can be dispersed in fcc Al matrix that are stable at temperatures ~ 400°C due to very low diffusivity of transition metals (Sc, Zr, Hf etc.) in the matrix. However, due to low solid solubility of these transition metals, the obtained volume fraction of these precipitates in the matrix is not sufficient to provide adequate room temperature strength. In fcc Co matrix, stable Co3Ti phase with L12 ordered structure forms with cuboidal morphology. However, besides having lower melting point, the precipitates have large misfit that lowers thermal stability at high temperatures. Recently, addition of Al and W with a proper ratio in Co is reported to lead the formation of metastable Co3(Al,W) L12 ordered phase in fcc α-Co matrix. This provides significant strength at high temperatures (~ 900°C). The main drawback for these alloys is their high densities (9.6 to 10.5 gm.cm-3) due to the requirement of compulsory addition of W (~ 15 to 25 wt%) for stabilising the ordered phase. In the present work, these problems are overcome leading to the development of new class of Al and Co alloys. The thesis is organized in three parts. In the first part, the principles of strengthening that can be optimized to develop newer high temperature high strength alloys are reviewed. The ordered L12 structure, which is the mainstay of the current effort of new alloy development, is elaborated. In the second part we present the results of our effort to the development a new class of high strength high temperature Al alloys. A new approach has been adopted to get a microstructure that contains both high temperature stable and room temperature strengthening precipitates. This has been illustrated by two Al rich compositions, Al-2Cu-0.1Nb-0.15Zr and Al-2Cu-0.1Hf-0.15Zr (at% unless stated otherwise). Addition of Nb/Zr or Hf/Zr in Al alloys leads to the formation of high temperature stable L12 ordered spherical coherent precipitates in the fcc Al matrix. Cu addition gives room temperature strengthening θ’ and θ” precipitates. The arc melted alloys were chill cast (suction cast) in the form of 3 mm rods followed by a novel three stage heat treatment process, as shown below. In the case of Al-2Cu-0.1Nb-0.15Zr alloy, the chill cast structure consists of Cu rich phase at the boundaries along the α-Al dendrites while Zr and Nb partition inside the α-Al dendrites. Aging at 400°C leads to an increase in the hardness of the cast alloy due to the precipitation of coherent L12 ordered Al3(Zr,Nb) spherical precipitates (~5nm) in the α-Al dendrites. Zr strongly partitions to the L12 ordered precipitate relative to the matrix. Nb exhibits weak partitioning in the precipitate. Further solutionising was optimized at 535°C for 30 minutes such that the segregation of Cu in the chill cast samples can be eliminated. The WDS mapping shows that Cu dissolved uniformly in the α-matrix while the Zr/Nb enriched α-Al dendrites are still present. The L12 ordered precipitates are mostly found in these Zr/Nb enriched dendrites formed during solidification. The precipitates sizes are finer (~5 nm) in dendrites and larger in the interdendritic region. The Nb partitioning increases in the ordered L12 precipitates relative to the matrix after solutionising. On aging at 190°C, fine θ” precipitates nucleate on prior Al3(Zr,Nb) precipitates present in α-Al dendrites while the interdendritic regions contain coarser θ’ nucleated on larger size L12 precipitates. The θ”/θ’ are much finer and higher in number density for the quaternary alloy compared to binary Al-2Cu alloy subjected to conventional heat treatment. The quaternary alloy show higher peak hardness of 1500 ± 8 MPa after 5 hours of aging at 190°C compared to binary Al-2Cu alloy with peak hardness of 1260 ± 11 MPa.

The concentration and composition of aerosols in the atmosphere over the Barents Sea were studied. Earlier, the contribution of aerosols to the formation of the Arctic environment was underestimated. Our data indicated a noticeable effect of continental aerosol on the atmosphere of the Barents Sea. The relationship of the black carbon concentration and the type of air masses has been established. Its concentration increases hundreds of times in the atmosphere of the sea when continental air is removed. The ionic composition and the content of chemical elements in the insoluble fraction of aerosols of the air over the Barents Sea were studied. The content of most chemical elements (Na, Al, K, Ca, Sc, Fe, Co, Rb, Zr, Cs, Ba, REE, Hf, Ta, Th, U) in the insoluble fraction of aerosols was below the average values for the upper continental crust. The content of Cr, Cu, Zn, As, Se, Br, Ag, Sb, Au, Pb is significantly higher than their average for the upper continental crust, due to the influence of the anthroposphere. Probable sources of anthropogenic pollution of aerosols in the Arctic are discussed.