Properties of high strength Al85La10Ni5 alloy

High strength Al₈₅La₁₀Ni₅ alloy with less than 3% porosity has been obtained under certain pressing and heating conditions by a powder metallurgy method (P/M). The compression strength and the hardness of the P/M aluminum alloy reach 950 MPa and HRc 32, respectively. The wear resistance of the alloy pressed at 753 K is twice of the conventional aluminum alloy A355. The high strength and wear resistance of the P/M aluminum alloy is attributed to second-phase strengthening and fine-grain strengthening.     

Laser-induced self-propagating reaction synthesis of amorphous-based composite Zr-Al-Ni-Cu alloys

Strong exothermic reaction due to large negative enthalpy of mixing can occur among major components of bulk metallic glass forming alloy systems. Based on this idea, we developed a new technique to fabricate amorphous-based composite materials using Laser-induced Self-propagating Reaction Synthesis (LSRS). The LSRS of the Zr₅₅Al₁₀Ni₅Cu₃₀ alloy shows that the products mainly consist of the amorphous, Zr₃Al₂ and Zr₂Cu phases. Hardness and wear resistance of the produced composite alloys are measured and are compared to the single amorphous phase alloy of the same composition.     

Crystallization of amorphous Al84.2Ni10La2.1Ce2.8Pr0.3Nd0.6 alloy

The crystallization of amorphous Al_84.2Ni₁₀La_2.1Ce_2.8Pr_0.3Nd_0.6 alloy was investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) techniques. The amorphous Al_84.2Ni₁₀La_2.1Ce_2.8Pr_0.3Nd_0.6 alloy crystallizes through the primary precipitation of fcc-Al phase from the amorphous matrix in the range of 490–550K, followed by the precipitation of Al₃Ni and Al₁₁(La, Ce)₃ phases in the temperature range of 590–680 K. Comparing amorphous Al_84.2Ni₁₀La_2.1Ce_2.8Pr_0.3Nd_0.6 and Al₈₄Ni₁₀Ce₆ alloys, the addition of La can improve the precipitation of primary fcc-Al phase upon reheating the samples. On the basis of the Kissenger equation, the activation energy for crystallization of Al₃Ni phase is higher than that of the other two phases, fcc-Al and Al₁₁(La, Ce)₃ phases, implying that the thermal stability of the Al₃Ni phase is higher than that of the other two phases.     

The influence of heat treatment on the corrosion behaviour of as-spun amorphous Al88Ni6La6 alloy in 0.01 M NaCl solution

The effect of the heat treatment on the corrosion behaviour of amorphous Al₈₈Ni₆La₆ made by melt-spun has been investigated by electrochemical measurements. Heat treatment was carried out at 523 K and 673 K for 4 min and 15 min respectively. The evolution of the crystallization process after annealing was identified by differential scanning calorimeter (DSC) as well as X-ray diffraction. The XRD patterns show that the structure of samples heat-treated at higher temperature changes towards a crystal state. The results obtained from the polarization curves reveal that all Al₈₈Ni₆La₆ alloys exhibit spontaneously passivated behaviour. Furthermore, it is noted that the partially crystallized alloy has the best corrosion resistance in comparison with as-spun amorphous and fully crystallized alloys, while the fully crystallized sample shows deterioration in the corrosion resistance.     

Influences of Similar Elements on Glass Forming Ability and Magnetic Properties in Al-Ni-La Amorphous Alloy

Similar element substitution has been applied for improving glass forming ability (GFA) in Al₈₆Ni₉La₅ amorphous alloy. The effects of La-Ce and Ni-Co pairs on the GFA, magnetic properties and hardness of Al-Ni-La alloy were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), magnetometer and hardness-tester. The results show the GFA of the samples in the order of Al86(Ni_0:5Co_0:5)9(La_0:5Ce_0:5)5< Al₈₆Ni₉La₅<Al₈₆Ni₉(La_0:5Ce_0:5)₅, implying that similar element substitution has a limited enhancing effect on the GFA of the present Al-Ni-La alloy. In addition, the measured samples display a diamagnetic behavior at room temperature. The variations of diamagnetic behavior as well as the microhardness of the samples are strongly dependent on the icrostructure, i.e., the amounts of the icosahedral structure and precipitates, after the similar element substitution in the Al-Ni-La alloy.     

Temperature and strain rate dependence of deformation behavior of Zr65Al7.5Ni10Cu17.5

In this work, the effects of temperature and strain rate on the deformation behavior of Zr₆₅Al_7.5Ni₁₀Cu_17.5 bulk metallic glass (BMG) were investigated. It was found that both temperature and strain rate had a significant influence on the deformation behavior of the BMG. The alloy exhibited Newtonian behavior at low strain rates but showed non-Newtonian behavior at high strain rates in the supercooled liquid region. However, the crystallization occurred slightly at a strain rate of 2 × 10^?4 s^?1 at the temperature of 693 K that is lower than the crystallization temperature Tx of Zr₆₅Al_7.5Ni₁₀Cu_17.5 BMG. The deformation mechanisms were discussed in terms of the transition state theory based on the free volume model.     

Dependence of GFA and Crystallization Behaviors of Al86Ni9La5 Metallic Glass on Its Original Liquid State

During the heating process the temperature‐induced liquid–liquid structure transition (LLST) of Al₈₆Ni₉La₅ melt from 1320 to 1490 K was identified by both electrical resistivity and differential thermal analysis measurement. The effects of liquid structural change on the crystallization behavior and glass forming ability (GFA) of Al₈₆Ni₉La₅ alloy were investigated. The amorphous samples prepared at different melt temperatures according to the liquid states were obtained. The results showed that the formation of intermetallic compounds during the crystallization process of the samples prepared below and within the LLST temperature range was earlier than that prepared above the LLST temperature range. The sample prepared above the LLST temperature range had the lowest GFA.     

Wear behaviour of 85Al–10La–5Ni alloy prepared by powder metallurgy

Abstract

The dry wear behaviour of 85Al–10La–5Ni (at.-%) alloy hot pressed has been studied. The result shows that 85Al–10La–5Ni alloy possessed excellent wear resistance. The wear resistance of the alloy pressed at 773 K is three times as high as that of the A355 aluminium alloy. The fine high hardness intermetallic compounds contribute to the wear resistance of the alloy.     

Electrochemical behavior of partially crystallized amorphous Al86Ni9La5 alloys

The Al₈₆Ni₉La₅ amorphous ribbons were annealed at 503 K for different time to obtain partially crystallized alloys with the different volume fractions of α-Al phase, and the effect of the crystallization extent on the electrochemical behavior of the ribbon was investigated in 0.01 M NaCl solution. The results show that the corrosion resistance of the partially crystallized ribbons is higher than that of the as-spun ribbon with the fully amorphous structure, and the corrosion resistance of the partially crystallized alloy is strongly dependent on the volume fraction of α-Al phase. The partially crystallized ribbon containing about 20 vol% α-Al phase exhibits the highest corrosion resistance.     

Synthesis and thermal stability of ball-milled and melt-quenched amorphous and nanostructured Al-Ni-Nd-Co alloys

In this work the Al₈₅Ni₉Nd₄Co₂ alloy was used as a starting point for examining the possibility of forming bulk glassy Al-based materials by combining rapid quenching and ball milling techniques. Fine glassy powders were obtained by ball milling melt-spun amorphous ribbons using a severe cryogenic processing regime. The thermal stability data of the powders as obtained by constant-rate heating and isothermal DSC experiments together with viscosity measurements are discussed with respect to feasible consolidation conditions. The powder compaction was done by two methods (uni-axial hot pressing and extrusion) at 513 K for up to 15 min. Only the uni-axial hot pressing led to bulk Al₈₅Ni₉Nd₄Co₂ samples with similar glassy structure and Vickers microhardness values comparable to those of the initial melt-spun ribbons.     

Synthesis of Al–Mn–Ce alloy by the spark plasma sintering

The bulk Al₉₀Mn₈Ce₂ alloy is sintered by spark plasma sintering (SPS) method. The microstructures and the hardness and wear resistance of the Al₉₀Mn₈Ce₂ samples are investigated. The results show that bulk Al₉₀Mn₈Ce₂ alloy with less than 2% porosity has been obtained at 673 K. At 723 K the Rockwell hardness of the alloy reaches 97 HRB and the wear resistance of the alloy is three times as high as that of the conventional A390 aluminum alloy. The high wear resistance of the Al₉₀Mn₈Ce₂ alloy is attributed to the existence of the large amount of the intermetallic compounds.     

The effect of titanium addition on the microstructure,mechanical and tribological properties of Ni3Si alloys prepared by powder metallurgy method

Ni₃Si alloy with different content of titanium was fabricated by powder metallurgy method. The microstructures, hardness and tribological properties of the alloys were investigation. The results showed that pure Ni₃Si alloy was composed of β₁‐Ni₃Si phase and γ‐Ni₃₁Si₁₂ phase, and Ni₃Ti phase formed with titanium addition. The hardness of the alloy decreased with the increasing titanium content. The friction coefficient of pure Ni₃Si alloy increased with the increasing load, while the friction coefficient of the alloy with titanium addition decreased. The wear rates of the alloys were all increased with increasing load, and the alloy with 5 % titanium addition had the best wear resistance properties. The wear mechanisms of the alloys were abrasive wear at low load, and the wear mechanisms changed to oxidative wear at high load.     

Lamp processing- and heat treatment-induced structural transformations of an amorphous Al<Subscript>85</Subscript>Ni<Subscript>10</Subscript>La<Subscript>5</Subscript> alloy: Hardness and local plasticity

We have studied the structural transformations and deformation behavior of an amorphous Al₈₅Ni₁₀La₅ alloy during nanoindentation and uniaxial tension tests and assessed the influence of crystalline phases resulting from lamp processing and heat treatment. Our results confirm the high effectiveness of lamp processing: at identical phase compositions, the lamp processing time is shorter by more than two orders of magnitude. The microplasticity of the amorphous alloy has been shown to manifest itself in both nanoindentation and uniaxial tension tests. The high proportion of local plasticity in the work of indentation has been accounted for in terms of possible intercluster sliding. The observed lamp processing- and heat treatmentinduced changes in the hardness of the alloy reflect changes in its phase composition and the percentages of the amorphous and crystalline phases, which does not rule out a cluster mechanism of local deformation or its deceleration by nanocrystalline phases in the amorphous–nanocrystalline structure.     

Diffusion bonding of Zr55Cu30Ni5Al10 bulk metallic glass to Cu with Al as transition layer

In this work we demonstrate the diffusion bonding of Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glass (BMG) to aluminum and copper alloy. The process parameters including temperature, pressure and time are investigated experimentally, and we obtain appropriate ones for accomplishing diffusion bonding of the BMG to aluminum alloy successfully. Then we present a two-step diffusion bonding process to bond the BMG to copper alloy by using aluminum alloy as transition layers, and achieve a five-layer bonded joint of BMG/Al/Cu/Al/BMG. The mechanical properties of the multilayer joint are examined. The hardness of the BMG in the joint is enhanced while the bending strength decreases significantly compared with the as-received BMG. Besides, the crystalline metals alleviate and block the extension of cracks in the BMG, which results in the joint fracturing in an explosion-proof glass manner, dissimilar to rupturing in a catastrophic manner that is always happened in the BMGs. Therefore, diffusion bonding of BMG to crystalline metals is a promising way to extend its application.     

Laser cladding of Zr65Al7.5Ni10Cu17.5 amorphous alloy on magnesium

Laser cladding of amorphous alloy Zr₆₅Al_7.5Ni₁₀Cu_17.5 on magnesium substrate was conducted using the blown powder method. The thickness of the coating was about 1.5 mm. The resulting microstructure, wear resistance and corrosion resistance of the coating were studied. The results of the XRD and TEM analyses showed that up to a depth of 1.1 mm, the coating had an amorphous structure, and no apparent crystalline structures were found. The coated specimen exhibited wear and corrosion resistance superior to that of the uncoated specimen: the wear loss was significantly reduced, some thirteen-fold; and the corrosion current was lowered by three orders of magnitude.     

Room-temperature sliding wear properties of laser melt deposited Cr13Ni5Si2/γ alloy

A wear-resistant alloy consisting of Cr₁₃Ni₅Si₂ ternary silicide dendrites and the interdendritic nickel-base solid solution (γ) was designed and fabricated by the laser melting/continuous deposition (LMCD) process. The wear resistance of Cr₁₃Ni₅Si₂/γ alloy was evaluated on an MM-200 block-on-wheel dry sliding wear tester at room temperature. Results indicate that the Cr₁₃Ni₅Si₂/γ alloy has excellent wear resistance and extremely low load-sensitivity of wear under dry sliding wear test conditions due to the high toughness and the high strength, as well as the transferred cover-layer on the worn surface of the alloy. Translated from Acta Metallurgica Sinica, 2006, 42(2): 181–185 [译自: 金属学报]     

Devitrification of nano-scale icosahedral phase in (Ti0.33Zr0.33Hf0.33)50(Ni0.5Cu0.5)40Al10 alloy with enlarging supercooled liquid region

This letter reports devitrification of novel multicomponent (Ti_0.33Zr_0.33Hf_0.33)₅₀(Ni_0.5Cu_0.5)₄₀Al₁₀ alloy, developed by equiatomic substitution. The supercooled liquid region of the (Ti_0.33Zr_0.33Hf_0.33)₅₀(Ni_0.5Cu_0.5)₄₀Al₁₀ alloy increased with progress of the first exothermic reaction. The supercooled liquid region of 57 K in the as-quenched state was observed to increase to 108 K after heat treatment for 180 min at 743 K. The corresponding microstructure after heat treatment for 180 min at 743 K consisted of a homogeneous distribution of the nano-scale icosahedral phase embedded in the remaining amorphous matrix. Therefore, it is feasible to understand that the devitrification of the nano-scale icosahedral phase occurs in the (Ti_0.33Zr_0.33Hf_0.33)₅₀(Ni_0.5Cu_0.5)₄₀Al₁₀ alloy by the primary crystallization.     

Improved properties of A319 aluminum casting alloy modified with Zr

The beneficial effects of 0.15 wt.% Zr addition on mechanical properties and wear resistance of A319 aluminum casting alloy were investigated. The cast alloys were given a solutionizing treatment followed by artificial aging in the temperature range 175 to 235 °C for different period of times. Mechanical properties and wear behavior of the Zr-containing material were determined and compared to those of the base A319 alloy in both as-cast and age-hardened conditions. It is shown that minor addition of Zr results in the precipitation of Al₃Zr particles in the aluminum matrix. These particles are stable upon heating due to the low solubility of zirconium in aluminum matrix. The main effects of such particles are an increase in hardness, strength, quality index and wear resistance. This is very promising where these aluminum cast alloys are to be used at relatively high temperatures.     

Crystallization kinetics of Zr60Al15Ni25 bulk glassy alloy

The crystallization kinetics of Zr₆₀Al₁₅Ni₂₅ bulk glassy alloy under isochronal and isothermal conditions has been investigated by differential scanning calorimetry (DSC). The microstructure of as-cast Zr₆₀Al₁₅Ni₂₅ bulk glassy alloy is observed by high-resolution electron microscopy (HREM). It is found that there exist nanocrystals with a size of about 7 nm in the glassy matrix, which are not observed in the XRD image. The results of Kissinger analysis show that the effective activation energies for glass transition (457 kJ/mol) and crystallization (345 kJ/mol) are high, indicating that it has large thermal stability against crystallization. The crystallization of Zr₆₀Al₁₅Ni₂₅ bulk glassy alloy under isothermal annealing can be modeled by the Johnson-Mehl-Avami equation. The crystallization kinetics parameters show that the isothermal crystallization starts from the growth of the pre-existing nanocrystals and the crystallization process is diffusion-controlled.