Al3Zr Phase Research Articles

Effect of Ti, Zr and Hf addition on microstructure and properties of rapidly solidified Al–Mn–Fe alloy

In this work, the influence of alloying elements Ti, Zr and Hf on microstructure and properties of Al91Mn7Fe2 melt spun ribbons, strengthened with quasicrystalline particles was studied. It was found that Zr improves significantly the microhardness of the alloy in as spun state by precipitation of metastable L12–Al3Zr phase in matrix grains. Both Hf and Zr additions retain higher microhardness values after annealing at 673K by formation of stable Al3X precipitates, even though the quasicrystalline phase being the main strengthening phase in the alloy starts to decompose. Comparison of the results from differential scanning calorimetry, thermo-mechanical analysis and microhardness measurements after annealing showed correlation between phase transformations and mechanical properties. Based on TEM studies, drop of microhardness and increase in Young’s modulus with temperature for all samples was attributed to significant change in samples microstructure, especially to decomposition of quasicrystalline particles and formation of different intermetallic phases.

Crystallography of Zr poisoning of Al-Ti-B grain refinement using edge-to-edge matching model

The mechanism of zirconium poisoning on the grain-refining efficiency of an Al-Ti-B based grain refiner was studied. The experiment was conducted by melting Al-5Ti-1B and Al-3Zr master alloys together. The edge-to-edge matching model was used to investigate and compare the orientation relationships between the binary intermetallic compounds present in the Al-Ti-B-Zr system. The results show that the poisoning effect probably results from the combination of Al3Zr with Al3Ti and the decreased amount of Ti solute, for Al3Ti particles have good crystallographic relationships with Al3Zr. Totally six orientation relationships may present between them, while they play vital roles in grain refinement. TiB2 particles appear to remain unchanged because of a bit large misfit. Only one orientation relationship may present between them to prevent Al3Zr phase from forming on the surface of TiB2, though TiB2 is agglomerated. The theoretical calculation agrees well with the experimental results. The edge-to-edge matching model is proved to be a useful tool for discovering the orientation relationships between phases.

A microstructural and crystallographic investigation of the precipitation behaviour of a primary Al3Zr phase under a high magnetic field

The effects of a high magnetic field on the precipitation behaviour of the primary Al3Zr phase are investigated. With and without the field, the primary Al3Zr crystals possess three morphologies – small tabular crystals in the deposit layer, long bars and dendritic crystals. The dendritic crystals are probably those surviving from the initial material. The tabular crystals in the deposit layer are those surviving from the heating stage, whereas the long bars are those formed during cooling. With the field, the tabular crystals in the deposit layer and the long bars tend to orient with the 〈110〉 direction parallel to the field direction, but the orientation of the dendritic crystals is less affected. The orientation of the crystals in the deposit layer arises from their magnetocrystalline anisotropy, but that of the long bars and dendritic crystals is disturbed by gravity and the formation of compound twins, respectively. Increased Zr content raises the precipitation amount of the primary Al3Zr crystals but weakens the alignment tendency of the tabular ones in the deposit layer. The weakness of the alignment arises from interaction between the crystals.

FIRST-PRINCIPLES INVESTIGATION OF THE THERMODYNAMICS PROPERTIES OF Al 3 Sc AND Al 3 Zr INTERMETALLICS

A first-principles investigation of the structural and thermodynamic properties of Al3Sc and Al3Zr intermetallics has been conducted using the norm-conserving pseudopotentials within the local density approximation in the frame of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the ABINIT code. The calculated formation enthalpy and cohesive energy results show that both phases have strong alloying ability and Al3Zr has a higher structural stability than Al3Sc phase. By means of calculations, the relationships of the vibrational free energy constant-volume specific heats entropy bulk modulus and thermal expansion with the elevated temperatures are given. The calculated bulk modulus indicates that Al3Sc and Al3Zr phases can improve the high-temperature creep resistance properties of aluminum alloys. The calculated datum of the thermal expansion and the diffusion speed of Sc and Zr in Al can explain the mechanism that the solder wire with Sc and Zr can improve the strength of welding gap and the resistance ability of hot crack.

On the mechanism of the formation of primary intermetallics under ultrasonic melt treatment in an Al-Zr-Ti alloy

Ultrasonic melt treatment (UST) is known to induce grain refinement in aluminum alloys, especially when transition metals like Zr and Ti are present. The refinement of primary intermetallics (e.g. Al3Zr, Al3(Zr,Ti)) caused by UST may influence the subsequent solidification process when intermetallics act as nucleation sites. In this paper, an Al-Ti-Zr alloy is used to analyse the effect of different ultrasonic intensities on the formation of these primary intermetallics. The possible nucleation behaviour of Al3Zr particles during UST is also discussed and an edge to edge matching model is used to make a preliminary analysis of lattice mismatch between aluminum oxide and Al3Zr phase. The experimental results show that when UST is applied, the Al3(Zr,Ti) particles might nucleate on aluminum oxides and remain fine during solidification.

High temperature dry sliding friction and wear behavior of aluminum matrix composites (Al3Zr+α-Al2O3)/Al

High temperature dry sliding friction and wear characteristics of in situ composites (α-Al2O3+Al3Zr)/Al were investigated using a pin-on-disk machine. When the test temperature is at 373K, the wear rates increase and arrive at the highest value and then decrease with the further increase of sliding velocity. However, when the test temperature is increased to 473K, the wear rates of the composites decrease constantly with the rising of sliding velocity. The critical load transferring from stable friction to unstable friction is around 50N at a test temperature of 473K and a sliding velocity of 0.6m/s. With the increase of the reinforcement volume fraction, the wear resistance of the composites increases. However, the Al3Zr phase is detrimental to the further improvement in the wear resistance of the composites. With the increase of applied loads and test temperature, the abrasive wear, oxidation wear and adhesive wear are the main modes in the complex wear mechanisms of the composites.

Microstructure and high temperature wear of the aluminum matrix composites fabricated by reaction from Al–ZrO2–B elemental powders

The microstructural evolution and high temperature wear characteristics of aluminum matrix composites fabricated by reaction of Al–ZrO2–B elemental powders were explored. The amount of the Al3Zr phase in the composites decreased with the increase of the B/ZrO2 mole ratio. When the B/ZrO2 mole ratio reached 2, the Al3Zr components almost diminished and the resultant composites consisted of primarily fine α-Al2O3 and ZrB2 particles. At test temperature of 373K and the applied load of 20N, the wear rate of the composites increased and arrived at the maximum value before decreasing with the further increase of sliding velocity. However, when the test temperature was reached to 473K, the wear rate decreased constantly with the increase of sliding velocity. With the increase of B/ZrO2 molar ratio, both the wear rate and the friction coefficient of the composites decreased, while the subsurface deformation zone increases. The findings help us to broaden the application of aluminum matrix composites in areas where high temperature wear is a limiting factor.

Phase evolution and dendrite growth in laser cladding of aluminium on zirconium

Aluminium was laser clad on a pure zirconium substrate using the blown powder method. The microstructure across the laser-clad coating was studied. Starting from the bottom to the top surface of the coating, a series of phase evolutions had occurred: (Zr)→(Zr)+AlZr2+AlZr3→Al4Zr5+Al3Zr2→Al3Zr2+AlZr2→Al2Zr→Al2Zr+Al3Zr. This resulted in an epitaxial columnar crystal growth at the re-melt substrate boundary, a band of backward growth Al3Zr2 dendrites towards the lower half of the coating, and a two-phase eutectic dendritic growth of Al2Zr+Al3Zr towards the top of the coating. The evolution of the various phases and microstructures is discussed in conjunction with the Al–Zr phase diagram, the criteria for planar interface instability, and the theory of eutectic growth under rapid solidification conditions (the TMK model).

Crystallographic features of the primary Al 3Zr phase in as-cast Al-1.36 wt% Zr alloy

The habit and morphology of the primary Al 3Zr crystals formed during the solidification of Al-1.36 wt% Zr alloy were analyzed. It was observed that the crystals have a tabular habit. The longitudinal cuts of the smaller and larger sized crystals appear, respectively, in octagonal and rectangular forms. The primary crystals also appear in the dendritic form. A crystallographic study indicates that the smaller sized crystals are bound by {0 0 1}, {1 0 1} and {1 1 1} faceted planes, whereas the larger sized ones by {0 0 1} and {1 0 1} faceted planes. One compound twin with two variants is found in the dendritic crystals and the complete twinning elements are determined. The tabular habit of the primary crystals is attributed to the low roughness of {0 0 1} planes. The disappearance of {1 1 1} planes in the larger sized crystals result from their high roughness. The twin formation is realized by lattice shear plus local atom stacking fault accompanied by local atomic reshuffling. The dendritic crystals are the result of the formation of the compound twin.

Al-Pr-Zr (Aluminum-Praseodymium-Zirconium)

The Al-Pr phase diagram [Massalski2] shows the following intermediate compounds: aAlPr3 (D019, Ni3Sn-type hexagonal), bAlPr3 (L12, AuCu3-type cubic), AlPr2 (C23, Co2Si-type orthorhombic), aAlPr (AlEr-type orthorhombic), bAlPr (CeAl-type orthorhombic), Al2Pr (C15, MgCu2-type cubic), Al3Pr (Ni3Sn-type hexagonal), Al4Pr or bAl11Pr3 (D13, Al4Ba-type tetragonal), and aAl11Pr3 (aLa3Al11-type orthorhombic). The Al-Zr phase diagram [Massalski2] depicts the following intermediate phases: Al3Zr (D023-type tetragonal), Al2Zr (C14, MgZn2-type hexagonal), Al3Zr2 (Al3Zr2-type orthorhombic), AlZr (Bf, CrB-type orthorhombic), Al4Zr5 (Ga4Ti5-type hexagonal), Al3Zr4 (Al3Ir4-type hexagonal), Al2Zr3 (Al2Zr3-type tetragonal), Al3Zr5 (D8m, W5Si3-type tetragonal), AlZr2 (B82, Ni2In-type hexagonal), and AlZr3 (L12, AuCu3-type cubic). The Pr-Zr phase diagram is not known. No intermediate phases were found in this system by [2010She].

Effect of HIPing on microstructure and properties of spray formed Al–Li alloy UL40

Spray formed billets of Al–4Li–0·14Zr (wt-%) were processed by a combination of hot isostatic pressing (HIPing), homogenisation, and solution treatment and aging. Extensive oxidation damage occurred after homogenisation in air, but could be alleviated by using controlled atmosphere or by prior HIPing. The microstructure and tensile properties were studied at various stages of processing. The volume fraction of AlLi (δ) decreased successively after HIPing, homogenisation and T6 temper, redistributing itself towards grain boundaries. The Al3Zr (β') phase was absent in the as formed condition, but precipitated after HIPing at 838 K/4 h and/or stepped homogenisation finishing at 838 K/4 h. Room temperature tensile properties were poor in the as spray formed condition, but improved after HIPing, homogenisation and T6 treatment successively. The tensile properties of the alloy were also evaluated between 648 and 848 K, for preliminary identification of optimum hot working parameters. HIPing did not affect high temperature yield strength significantly, but increased the ductility.

Dry sliding wear behavior of Al-based composites fabricated by exothermic dispersion reaction in an Al–ZrO 2–C system

In situ Al-based composites were fabricated by exothermic dispersion method. Dry sliding wear results showed that the original C/ZrO 2 mole ratio is a key factor to the wear behavior of the composites. When the ratio of C/ZrO 2 = 0, the reinforcements are mainly composed of Al 3Zr particles and α-Al 2O 3 particles, and it is suggested that the dominant wear mechanism is abrasive wear. The wear resistance of the composites is not satisfactory due to the low mechanical strength and brittleness of the Al 3Zr phase. When the C/ZrO 2 ratio increases from 0 to 1, the wear resistance is significantly improved by the increased volume fraction of α-Al 2O 3 and decreased volume fraction of Al 3Zr, plus newly formed nanosized ZrC particles. Moreover, experimental results showed that the mass loss of the composites linearly increases with the sliding distance. The wear rates decrease with the increment of the sliding velocity, but increase with the C/ZrO 2 mole ratios. When the C/ZrO 2 mole ratio is increased, the friction coefficients of the composites reduce, and the wear surface becomes smoother. When the C/ZrO 2 = 1, the produced ceramic reinforcements are composed of nanoscaled α-Al 2O 3 phase and ZrC phase, without Al 3Zr phase. Under this circumstance, it is proposed that the adhesive wear becomes the predominant, and the composites have the best wear resistance and friction properties.

Structure and properties of Al-Mg-Si alloys with Zr and Sc additions produced by melt spinning and twin rolling casting techniques

Aluminium alloys with 1 wt.% Mg, 0.6 wt.% Si and 0.5 wt.% Zr, or 0.5 wt.% Zr + 0.2 wt.% Sc additions were cast using different techniques such as: conventional stationary mould casting, twin rolling and melt spinning. Microstructure studies have shown that a significant grain refinement down to 20 µm was obtained in the alloy containing 0.5 % Zr + 0.2 % Sc cast to a copper mould due to the presence of Al3(Zr, Sc) primary particles. Columnar grains near the surfaces and equiaxial ones in their central part were observed in strips obtained by the twin rolling method, while the ribbons of thickness 70–100 µm, cast using melt spinning, revealed equiaxial grains of an average diameter of 2–3 µm. The additions of Sc and Zr brought about a small increase of microhardness only in the mould cast alloys and strips while no changes in microhardness have been observed in alloys prepared using various casting techniques. The alloys produced by both unconventional casting techniques were annealed at the temperature range of 400–540 ◦ C, which resulted in the precipitation of either Al3Zr or Al3(Zr, Sc) phases from the Al solid solution in the form of spherical (about 10 nm large) particles as well as an additional microhardness increase up to about 130 HV for the AlMg1Si0.6Zr0.5Sc0.2 alloy. K e y w o r d s : aluminium alloys, rapid solidification, melt spinning, microindentation, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX)

Effect of quaternary zirconium addition on mechanical properties of Al-6Mg-Sc (0.2-0.6%) alloy studied by ANN technique

The addition of scandium in Al-Mg alloys forms a LI2 phase, Al3Sc, which precipitates coherently. The ability of Al3Sc precipitates to stabilise the substructures envisages the use of strain hardening for enhancement of mechanical properties of the alloy. Al3Zr phase possess similar crystal structure as that of Al3Sc. Hence the present study aims to address the influence of quaternary addition of zirconium in Al-Mg-Sc alloys through Artificial Neural Network (ANN) models. The effect of composition and ageing parameters on the variation of tensile properties for Zr added Al-Mg-Sc alloys is successfully predicted by ANN technique.

Synthesis and thermal stability of novel amorphous Al70Fe25Zr5 alloy prepared by mechanical alloying

A novel amorphous Al70Fe25Zr5 alloy was synthesised through high energy ball milling the mixtures of Al, Fe and Zr powder with the milling intensity of 150G (G is the gravitational acceleration). By comparing with the binary Al–Fe amorphous, differential scanning calorimeter results indicated the crystalline temperature of ternary Al70Fe25Zr5 amorphous alloy shifts higher temperature, and it showed two stages of crystalline reactions which corresponded to the formation of Al5Fe2 and Al3Zr phases respectively. Improvement of the thermal stability for this novel Al70Fe25Zr5 amorphous alloy is explained in terms of the total structure factor that was determined by the X-ray diffraction method.

Thermodynamic assessment of the Fe–Al–Zr phase diagram

The thermodynamic assessment of the Fe–Al–Zr ternary system was performed using the CALPHAD technique. The four published isothermal sections at 1073, 1173, 1273 and 1423 K, together with the proposed liquidus surface and the corresponding invariant reaction scheme, were taken into account. The reliability of the previous binary assessments was checked for the systems of interest, namely, for the Fe–Zr, Zr–Al and Fe–Al systems. Reassessment of the C15 Laves phase of the Fe–Zr system has been done to obtain a better description of the phases in the ternary system. The solution phases, including liquid, α -Fe, γ -Fe, α -Zr, β -Zr and γ -Al, were modelled as substitutional solutions, while the new ternary phases ( τ 1 , τ 2 and τ 3 ) were modelled as linear and stoichiometric compounds, respectively. The C14 and C15 Laves phases have been assessed using a two-sublattice model. Any ternary solubility of the other binary phases was not taken into account in the ternary assessment. The liquidus projection and several isothermal sections were calculated, and they agreed reasonably well with the reported experimental data.

Microstructure and mechanical properties of Al–Zr nanocomposite materials

Three different processing routes were explored to develop Al–Zr nanocomposite alloys using mechanical alloying and spark plasma sintering methods. Depending on the route of milling adopted, the powder in the as-milled condition consisted of either a solid solution of Zr in Al or a mixture of Al-solid solution and Al 3Zr (L1 2) phases. The alloys after sintering consisted of Al and Al 3Zr (L1 2) with grain sizes of less than 100 nm. These nanocomposite alloys exhibited a high compressive strength of 1 GPa with 10% plasticity. The high strength observed in these alloys was explained on the basis of the retention of nanometer sized grains and also the fine dispersion of the L1 2 phase. On the other hand, the good amount of plasticity was explained to be due to excellent bonding between the powder particles and the presence of coarse Al grains in the matrix.

Structural，elastic and electronic properties of L12 aluminum phases from first principles calculation

First principles calculations are performed to study structural， elastic and electronic properties of typical L12 precipitates of Al-based alloys （Al3Sc and Al3Zr）. The calculated formation energy and the cohesive energy show that both typical L12 precipitates of aluminum alloys have a strong alloying ability and Al3Zr phase has a higher structural stability than Al3Sc phase. According to the calculated density of states of these phases， it is found that the higher structural stability of Al3Zr is attributed to an increase in the number of bonding electrons below Fermi level. Three independent single-crystal elastic constants （C11，C12 and C44） at zero-pressure as well as polycrystalline mechanical parameters such as bulk modulus B， shear modulus G， Youngs modulus Y， Poissons ratio ν and anisotropy value A for both phases are calculated. The mechanical properties of both phases are further analyzed and discussed in comparison with experimental observations and other theory results.

Microstructure and mechanical properties of a large billet of spray formed Al–Zn–Mg–Cu alloy with high Zn content

In this study, a large billet of Al–12Zn–2.4Mg–1.1Cu–0.5Ni–0.2Zr alloy was prepared by spray deposition technique, the billet was subsequent processed by hot extrusion, solid solution treatment at 758 K and aging at 393 K for 20 h. The aged alloy was then subjected to tensile testing, it was shown that yield strength, tensile strength and elongation rate of the alloy reached 689 MPa, 750 MPa and 11%, respectively. The composition, microstructure and fracture characteristics of the tensile sample were explored by EDS (energy dispersive spectrometer), optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. A spherical morphology of the primary α-phase was observed in the spray-deposited Al alloy, dispersed and fine-scale L1 2–Al 3Zr phases, GPII zones and η′ precipitates, were also evident in the microstructure of the aged alloy. Fracture analysis of the tensile sample exhibited transgranular fractographic features. We suggest that precipitate-phase hardening and solid solution strengthening were responsible for reinforcing of the spray-deposited alloy.

Influence of atomized powder size on microstructures and mechanical properties of rapidly solidified Al–Cr–Y–Zr aluminum alloys

Rapidly solidified powders of Al–5.0Cr–4.0Y–1.5Zr (wt%) were prepared by using a multi-stage atomization-rapid solidification powder-making device. The atomized powders were sieved into four shares with various nominal diameter level and were fabricated into hot-extruded bars after cold-isostatically pressing and vaccum degassing process. Influence of atomized powder size on microstructures and mechanical properties of the hot-extruded bars was investigated by optical microscopy, X-ray diffraction, transmission electronic microscopy with EPSX and scanning electron microscopy. The results show that the fine atomized powders of rapidly solidified Al–5.0Cr–4.0Y–1.5Zr aluminum alloy attains supersaturated solid solution state under the exist condition of multi-stage rapid solidification. With the powder size increasing, there are Al20Cr2Y (cubic, a = 1.437 nm) and Ll2 Al3Zr (FCC, a = 0.407 nm) phase forming in the powders, and even lumpish particles of Al20Cr2Y appearing in the coarse atomized powders, as can be found in the as-cast master alloy. Typical microstructures of the extruded bars of rapidly solidified Al–5.0Cr–4.0Y–1.5Zr aluminum alloy can be characterized by fine grain FCC α-Al matrix with ultra-fine spherical particles of Al20Cr2Y and Al3Zr. But a small quantity of Al20Cr2Y coarse lumpish particles with micro-twin structures can be found, originating from lumpish particles of the coarse powders. The extruded bars of rapidly solidified Al–5.0Cr–4.0Y–1.5Zr aluminum alloy by using the fine powders eliminated out too coarse powders have good tensile properties of σ0.2 = 403 MPa, σb = 442 MPa and δ = 9.4% at room temperature, and σ0.2 = 153 MPa, σb = 164 MPa and δ = 8.1% at high temperature of 350 °C.