Al-4 Wt Research Articles

Corrosion behaviors of single-layer and double-layer nickel alloy coatings fabricated by arc spraying and high-velocity oxy-fuel

This study investigates single-layer and double-layer thermally sprayed nickel alloy coatings (bond and top coatings). Ni-5 wt% Al and Ni-20 wt% Cr were used as bond coatings, whereas highly alloyed Ni-based coatings, Hastelloy C276 or Inconel 625 were used as top coatings. Arc spraying (A) and high-velocity oxy-fuel (HVOF) techniques were used to create the coatings on a 304 stainless steel substrate. The samples were studied by performing potentiodynamic polarization tests in a 20 vol% H2SO4 solution at room temperature. The scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) techniques were used to investigate the microstructure and chemical composition of the coatings. The arc sprayed coatings are composed of a lamellar microstructure with low porosities, unmelted particles, and high oxides at the intersplats. A uniform and compact coating with minimal oxides and porosity was achieved for all coatings via HVOF technique. In single-layer coatings, arc spray coating surpasses HVOF coating owing to its oxide layers, which impede sulfuric solution penetration and bolster resistance against electrolyte infiltration. Double-layer coatings, comprising a bonding layer and a top coating, using the same thermal spray method have shown to enhance corrosion resistance.

New quaternary eutectic Al-Cu-Ca-Si system for designing precipitation hardening alloys

The aluminum corner of the previously unexplored quaternary eutectic Al-Cu-Ca-Si system promising for the design of new heat treatable alloys have been studied using thermodynamic modeling and experimental techniques. The experimental data have revealed the presence in equilibrium of a previously undescribed quaternary compound identified as a strict stoichiometric Al2CaSiCu phase with a tetragonal I4/mmm structure (Pearson symbol: tI10) and the lattice parameters a = 4.04 Å and c = 11.00 Å. The phase has a density of 3.36 g/cm3 and a microhardness of 335 Hv. In accordance with the suggested structure of the phase diagram, its region that can be promising for the design of heat treatable alloys contains three (Al)+Al2Cu+Al2CaSiCu, (Al)+Al2Si2Ca+Al2CaSiCu and (Al)+Al2Cu+Al2Si2Ca quasi-ternary sections and two (Al)+Al2Cu+Al2Si2Ca+Al2CaSiCu and (Al)+Al2Cu+Al2CaSiCu+Si four-phase fields. Analysis of the precipitation hardening response for the new quaternary Al-5 wt%Cu-Ca-Si alloys suggests that it is not inferior (the obtained peak hardness is ∼125 Hv) to that for the alloys Al-5 wt% Cu (∼120 Hv) and Al-4 wt%Si-5 wt%Cu (∼125 Hv) based on the conventionally used systems. However, to obtain noticeable hardening at aging, the content of silicon should be at least 1.1–1.2 times higher than that of calcium. A comparative hot tearing susceptibility (HTS) study revealed that the new heat treatable Al-5 wt%Cu-Ca-Si alloys have higher hot tearing resistances (HTS ∼16 mm according to a pencil probe) than that of the Al-5 wt%Cu base alloy (HTS >16 mm).

High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites: Synthesis, mechanical, microstructural and thermal characterization

This study aims to introduce a novel type of particulate reinforced Al matrix composite. High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites were produced via a combined process of different powder metallurgy methods. Firstly, boride compounds (HfB2, TiB2, ZrB2, VB2, NbB2) were synthesized in the laboratory scale using the related metal oxide, boron oxide, and magnesium by mechanochemical synthesis (MCS) and leaching processes under optimum conditions. Secondly, the synthesized and purified boride powders were mixed in equimolar ratios using a planetary ball mill for 72 h, and they were sintered at 2000 °C under 30 MPa via spark plasma sintering (SPS). Thirdly, equimolar high entropy (HfTiZrVNb)B2 bulks were crushed, converted into powder forms, and added into Al powders at different amounts as 1, 2, 5, 10, and 15 wt %. Lastly, these powder blends were mechanically alloyed in a vibratory ball mill for 6 h, cold pressed and pressureless sintered at 630 °C for 2 h. For characterization techniques, X-ray diffractometry (XRD), thermal analysis, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), density measurements using pycnometer and Archimedes' methods, microhardness and dry sliding wear tests were conducted on the sintered composites. The highest hardness (∼1.5 GPa) and the lowest wear rate (∼0.0012 mm3/Nm) were obtained in the Al-15 wt % (HfTiZrVNb)B2 sample.

Influence of Zr Microalloying on the Microstructure and Room-/High-Temperature Mechanical Properties of an Al-Cu-Mn-Fe Alloy.

Here, 0.3 wt.%Zr was introduced in an Al-4 wt.%Cu-0.5 wt.%Mn-0.1 wt.%Fe alloy to investigate its influence on the microstructure and mechanical properties of the alloy. The microstructures of both as-cast and T6-treated Al-Cu-Mn-Fe (ACMF) and Al-Cu-Mn-Fe-Zr (ACMFZ) alloys were analyzed. The intermetallic compounds formed through the casting procedure include Al2Cu and Al7Cu2Fe, and the Al2Cu phase dissolves into the matrix and re-precipitates as θ' phase during the T6 process. The introduction of Zr results in the precipitation of L12-Al3Zr nanometric precipitates after T6, while the θ' precipitates in ACMFZ alloy are much finer than those in ACMF alloy. The L12-Al3Zr precipitates were found coherently located with θ', which was assumed beneficial for stabilizing the θ' precipitates during the high-temperature tensile process. The tensile properties of ACMF and ACMFZ alloys at room temperature and elevated temperatures (200, 300, and 400 °C) were tested. Especially, the yield strength of ACMFZ alloys can reach 128 MPa and 65 MPa at 300 °C and 400 °C, respectively, which are 31% and 33% higher than those of ACMF alloys. The strengthening mechanisms of grain size, L12-Al3Zr, and θ' precipitates on the tensile properties were discussed. This work may be referred to for designing Al-Cu alloys for application in high-temperature fields.

The mechanical properties of Al3Sc single crystal investigated by nanoindentation using Hertzian elasticity theory method and Oliver-Pharr method

The crystal structure, orientation, reduced modulus, and hardness of Al3Sc single crystal were studied using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and nanoindentation techniques, combined with Hertzian elastic theory method (Hertz) and Oliver-Pharr method (O&P). Millimeter-sized Al3Sc single crystals were prepared using quasi-equilibrium solidification of hypereutectic Al-15(wt %) Sc alloy. The XRD results showed that the samples were composed of L12-Al3Sc and Al phases. The EBSD and nanoindentation results showed that for five Al3Sc single crystals with different orientations, the reduced moduli measured by Hertz method were 146.6 ± 0.4–148.3 ± 0.2 GPa; while measured by O&P method they were 147 ± 2–150 ± 3 GPa. The corresponding hardnesses were varied between 3.8 ± 0.1 and 3.9 ± 0.1 GPa. The Poisson's ratio and elastic constants were determined through iterative calculation based on the relationship between the reduced modulus and Young’s modulus at various orientations. The polycrystal elastic properties, bulk modulus, shear modulus and Young's modulus, were determined. The elastic constants c11, c12, and c44 were 179.2 ± 0.4, 44.1 ± 0.1, and 68.3 ± 0.3 GPa, respectively; the Poisson's ratio was 0.196 ± 0.001. The Young's modulus of five Al3Sc single crystals oriented in different directions was in the narrow range 161–164 GPa. The anisotropy factor of Al3Sc crystal was 1.011 ± 0.002, confirming that it is elastically isotropic. These results provide fundamental information for the research and development of the Al3Sc intermetallic compound and related alloys in future.

In situ hydrogen production from Al–BiCl3 hydrolysis for small-sized fuel cell

Small-sized fuel cell has tremendous potential and broad market prospect in the field of portable devices, but its hydrogen source with compact structure and stable and high purity hydrogen supply remains an issue for commercialization. In this research, a novel in situ hydrogen production material Al–BiCl3 composite is developed via ball milling method, and its hydrogen production performance is evaluated in terms of induction time, storage stability, hydrogen production rate and hydrogen yield. The results demonstrate that Al–BiCl3 has excellent hydrogen production performance and its hydrogen yield can reach 85 % within 2.3 h. During ball milling process, many surface cracks and active surface are produced and some BiCl3 is reduced to metal Bi by Al, resulting in the high hydrolysis activity of Al–BiCl3. Prolonging milling time can promote the formation of surface cracks and Bi, enhancing the activity of Al–BiCl3. The hydrogen production mechanisms of Al–BiCl3 are attributed to pitting and microgalvanic effect between Al and Bi. Taking into account hydrogen production performance, cost and safety, Al-10 wt% BiCl3 milled for 1 h is a suitable and potential in situ hydrogen production material for small-sized fuel cells.

Lubricated Wear Properties of Zn-30Al-3Cu-Si Alloys

To assess the effect of silicon content (SC) and test parameters on the lubricated wear of Zn-30 wt.% Al-3 wt.% Cu-(0.5–5) wt.% Si alloys, six quaternary alloys were produced by casting. Their wear properties were investigated at different ranges of contact pressure (CP) of 1–8 MPa and sliding velocity (SV) of 1–3 ms−1 for two different sliding distances (SD) of 20 km and 108 km. It was observed that Si addition (SA) improved the tribological properties of Zn-30Al-3Cu alloy, but an increase in the SC above a certain percentage (0.5%) adversely affected these properties. Therefore, Zn-30Al-3Cu-0.5Si alloy demonstrated the lowest friction coefficient (FC) and wear volume (WV) among the alloys tested. The correlations between the lubricated wear properties (FC and WV) of the alloys and test conditions (CP and SV) were made by non-linear regression analysis using the wear test data. Finally, the equations for the relationship between the wear properties of the alloys and the test parameters were determined.

Improved Thermal Stability of Al-Si Alloy Coated Steel Sheet with Cr Thin Film Deposition

We investigated the effect of Cr thin film deposition on the thermal stability and corrosion resistance of hot-dip aluminized steel. A high-quality Cr thin film was deposited on the surface of the Al-9 wt. % Si-coated steel sheets by physical vapor deposition. When the Al-Si coated steel sheets were exposed to a high temperature of 500℃, Fe from the steel substrate diffused into the Al-Si coating layer resulting in discoloration. However, the highly heat-resistant Cr thin film deposited on the Al-Si coating prevented diffusion and surface exposure of Fe, improving the heat and corrosion resistances of the Al-Si alloy coated steel sheet.

Crystallography and Interface Structures in As-Arc Melted and Laser Surface-Remelted Aluminum–Silicon Alloys with and without Strontium Addition

The crystallography of the eutectic Al-Si microstructure in both unmodified and Sr (0.2 wt.%)-modified hypereutectic Al-20 wt.% Si alloys, processed via arc-melting and laser surface remelting, has been comprehensively characterized using transmission electron microscopy and electron diffraction. Although, under as-cast conditions, specific orientations between different planes of Al and Si, satisfying defined orientation relationships (ORs), have been investigated within the flake morphology, the rapid solidification induced by laser surface remelting results in a notable transformation from a flake morphology to nanocrystalline Si fibers dispersed in an Al matrix. Consequently, this transformation results in a mis-orientation of the interface between the eutectic Al and Si phases, preventing the formation of orientation relationships, thus promoting the formation of faceted interfaces exhibiting substantial lattice disregistry.

Effect of indium and yttrium on the corrosion behavior of AZ63 magnesium alloy

Indium (In) and yttrium (Y) can activate and alleviate the corrosion of magnesium alloy, respectively. The effects of 1 wt% In and 1 wt% Y on the microstructure and electrochemical behaviors of Mg-6 wt%Al-3 wt%Zn (AZ63) magnesium alloy are investigated via materials characterizations associated with electrochemical techniques. The results showed that co-alloying of In and Y would increase the number of intermetallic phases in AZ63 by generating discrete Al2Y phase and continuous Mg17Al12 phase. During the process of corrosion, the corrosion of Mg-6 wt%Al-3 wt%Zn-1 wt%In-1 wt%Y(AZ63InY) initiates from the intermetallic phases and propagates locally. The corrosion products are apt to adhere on the corroded surface, underneath which a severe corrosion takes place due to the enhanced dissolution-reprecipitation effect of In on activating Mg.

Characterization of wear rate of Al-12 wt%Si alloy based MMC reinforced with ZrO2 particulates

The primary objective of this study is to fabricate an Al-12 wt% Si Alloy/ZrO2 composite using the Stir Casting technique, with a specific focus on assessing its performance, particularly in terms of wear characteristics. This research presents a unique approach by utilizing Al-12 wt% Si Alloy as the matrix material, aiming to develop tailored Al Alloy matrix composites suitable for applications requiring enhanced tribological properties. The composites are systematically manufactured with varying percentages of micro-sized ZrO2 reinforcements, specifically 0.5, 1, and 3 wt%. The incorporation of ZrO2 results in significant improvements in wear resistance, a critical attribute for Al-12 wt% Si Alloy-based composites. These composites find extensive utility across industries such as marine, aerospace, automotive, and the power sector, where they are indispensable for producing vital components like electrical sliding contacts, gears, bearings, bushes, pistons, piston rings, and clutches. Despite the availability of various promising reinforcement materials, researchers persistently explore novel combinations of matrices and reinforcements to tailor properties and enhance cost-effectiveness. ZrO2 has emerged as a notable reinforcement material in metal matrix composites, as evidenced by numerous research endeavours. The composites fabricated with ceramic reinforcement’s exhibit enhanced tribological characteristics. The study observes that the wear rate decreases up to 3 wt% of reinforcements, beyond which it increases due to reinforcement agglomeration. The optimal wear-resistant combination is found at 3 wt% of ZrO2, attributed to robust micro-coring and interstitial metal-oxygen bonding facilitated by the Si content in the Al-12%Si matrix. The results are further optimized using Response Surface Methodology (RSM) techniques and validated using the ANOVA table to elucidate the behaviour of the composites under different operational conditions. The hardness results further ascertain the decrease in the wear rate due to the inclusion of ZrO2 reinforcements owing to micro coring and strengthening.

Effect of annealing time on microstructure and mechanical properties of Fe–C–Mn–Al–Si steel

Cold-rolled medium manganese steel (0.09C–7.23Mn–1.99Si–4.42Al wt-%) was investigated. The tested steel was treated by inter-critical annealing quenching and partitioning process. The effects of the annealing time on the microstructure and mechanical properties of the medium manganese steel were investigated by SEM, TEM, EBSD and XRD methods. The results show that, the tested steel consists of martensite, α-ferrite, δ-ferrite and retained austenite. The process has a significant effect on the diffusion of C/Mn elements and significantly changes the microstructure of the tested steel. At the same time, the austenite grain size and the degree of dispersion of its internal elements reach a balance, which is conducive to maintaining moderate stability of the massives retained austenite at room temperature.

Corrosion Behavior of As-Cast and Heat-Treated Al-Co Alloys in 3.5 wt% NaCl.

The present work evaluates the effect of Co content on the microstructure and corrosion performance of Al-Co alloys of various compositions (2-32 wt% Co), fabricated by flux-assisted stir casting. A preliminary investigation on the effect of heat treatment (600 °C, up to 72 h) on the microstructure and corrosion behavior of Al-20 wt% Co and Al-32 wt% Co was also conducted. The Al- (2-10) wt% Co alloys were composed of acicular Al9Co2 particles uniformly dispersed in an Al matrix. The Al-20 wt% Co and Al-32 wt% Co alloys additionally contained Al13Co4 blades enveloped in Al9Co2 wedges. Heat treatment of Al-20 wt% Co and Al-32 wt% Co led to a significant reduction in the volume fraction of Al13Co4 and a decrease in hardness. Al-Co alloys with high Co content (10-32 wt% Co) exhibited greater resistance to localized corrosion in 3.5 wt% NaCl, but lower resistance to general corrosion compared to the (0-5 wt% Co) alloys. Heat treatment led to a slight increase in the corrosion resistance of the Al-Co alloys. The microstructure of the produced alloys was analyzed and correlated with the corrosion performance. Finally, corrosion mechanisms were formulated.

Aging behaviors of the Al–Cu alloy via ultrasound-promoted thermal treatments

Aging treatments have been widely utilized for enhancing the mechanical properties of many materials, such as Al–Cu alloys. In conventional aging treatments, there is a trade-off between the aging conditions (e.g., aging times and temperatures) and the mechanical properties (e.g., hardness and strength). There is usually compensation in the aging treatments, such as deteriorated hardness of the alloys, when tuning the aging conditions. The ultrasound-promoted aging treatments were conducted in this study to solve the aforementioned conventional difficulties since it is believed that the ultrasound could accelerate the diffusion of the atoms and thus shorten the aging time while keeping the aging temperature low. The Al-4 wt.% Cu alloys were utilized for the verification of the influence of the ultrasound on the mechanical properties of the alloys since the Al-4 wt.% Cu alloys have been widely studied. It was found that with the promotion of the ultrasound, the micro Vickers hardness of the alloys could be enhanced. On the other hand, the alternations of strength and elongation by applying an ultrasound were limited. It is therefore concluded that the ultrasound could have certain positive effects on the enhancement of the alloy properties, such as micro Vickers hardness.

A comprehensive analysis of cooling curves, fluidity, inclusions, porosity, and microstructure of NaCl-KCl-NaF flux treated Al-12Si alloy

In this study, we investigated the effects of treating Al-12 wt% silicon alloy with an equimolar composition mixture of NaCl, KCl, and NaF on various aspects of the alloy’s properties. Key findings of the research indicate that the flux treatment had significant effects on the alloy. It led to increased nucleation temperatures and reduced undercooling, thereby facilitating nucleation sites and grain refinement. Additionally, the inclusion of flux reduced the entrapment of inclusions in the melt, which can potentially enhance the mechanical properties of the alloy. However, it also led to a larger and more widely distributed gas porosity in the solidified samples, as gas evolved from the flux trapped during solidification. Moreover, the flux treatment had noticeable impacts on the morphology of eutectic silicon particles, reducing their aspect ratio. These findings offer valuable insights into the potential benefits and challenges of sodium-based flux melt treatment in optimizing the quality of Al-12Si alloy castings, particularly in die-casting applications.

Fabrication of Al-Ni Alloys for Fast Hydrogen Production from Hydrolysis in Alkaline Water

Hydrogen generation through the hydrolysis of aluminum alloys has attracted significant attention because it generates hydrogen directly from alkaline water without the need for hydrogen storage technology. The hydrogen generation rate from the hydrolysis of aluminum in alkaline water is linearly proportional to its corrosion rate. To accelerate the corrosion rate of the aluminum alloy, we designed Al-Ni alloys by continuously precipitating an electrochemically noble Al3Ni phase along the grain boundaries. The Al-0.5~1 wt.% Ni alloys showed an excellent hydrogen generation rate of 16.6 mL/cm2·min, which is about 6.4 times faster than that of pure Al (2.58 mL/cm2·min). This excellent performance was achieved through the synergistic effects of galvanic and intergranular corrosion on the hydrolysis of Al. By raising the solution temperature to 50 °C, the optimal rate of hydrogen generation of Al-1 wt.% Ni in 10 wt.% NaOH solutions at 30 °C can be further increased to 54.5 mL/cm2·min.

Numerical simulation of VAR for large-scale TC4 alloy during the solidification process

ABSTRACT A three-dimensional multi-physics model of the effect of process parameters on the evolution of the solid–liquid interface during solidification of large-scale Ti-6 wt% Al-4 wt% V (TC4) alloy by[Ballantyne, 1977 #483] (VAR) and a macroscopic model of grain nucleation and growth was established. The simulation results qualitatively reveal the evolution of solid–liquid interface and central cross-sectional solidification structure under various melting conditions, indicating that the melting zone depth increased while the mushy zone width and the number of grains decreased with the increase of melting power; the depth of the melting zone and the width of the mushy zone increase sharply with the increase in solidification velocity, the average grain radius increased, while the number of grains decreased; when the ingot diameter increased from 260 mm to 660 mm, the depth of the melting zone increased and gradually remained stable, and the width of the mushy zone gradually decreased.

Additive manufacturing of a lightweight Al-Ca alloy by direct energy deposition and laser powder bed fusion

Abstract High strength and low density materials are needed to achieve lightweight design of components. Aluminum base metals alloyed with calcium are of potential interest because of the low density of calcium and its abundance. The additive manufacturing of dense and crack free samples out of an Al-10 wt.% Ca (Al-10Ca) alloy is presented. Both laser-based direct energy deposition (DED-LB) and laser powder bed fusion (LPBF) processes were applied to manufacture sample material. Preheating of the substrate plate is needed in LPBF to receive crack free samples. An analysis of the microstructure shows an Al-Al4Ca lamellar eutectic.

Solidification, α-Al morphologies, and tensile properties of low-Sc modified Al-Mg alloys

Al alloys are very attractive in engineering applications that require a combination of low density and mechanical strength, such as in aeronautical and aerospace industry devices. Therefore, the search for alloys with higher specific strength is justified from environmental and economic points of view. This work aims to study the influence of cooling rates on the phase morphology and tensile properties of ternary Al-Mg-Sc alloys, whose composition covers the spectrum of low-Sc Al-Mg-Sc alloys. The ternary Al-3, −5, and − 10 wt% Mg-0.1 wt% Sc alloys were processed by transient directional solidification. This process induces a wide range of cooling rates which causes the formation of a microstructural variety along the longitudinal cooling direction and, consequently, different tensile properties. Several characterization methods were employed, including: thermal analysis, x-ray diffraction (XRD) structural analysis, SEM-EDS, optical microscopy, CALPHAD, tensile tests, and fractography. Two major findings should be noted after fully characterizing the microstructures, the formed phases, and the tensile properties. Solidification evolution revealed that more Mg added resulted in higher solidification rates due to higher fluidity with more Mg. Furthermore, cell growth was mapped in the three alloy compositions while competing with dendrites. Solidification scaling relationships between dendritic or cellular spacing and cooling rate for all alloys were examined. Although the Al-10 wt% Mg-Sc alloy had more Mg in solid solution, the Al-5 wt% Mg-Sc alloy showed superior tensile strength due to the predominance of cells and thinner primary dendrites trunks forming its microstructure.

Effect of Addition of Cerium Oxide, Cryolite, and Zirconium on Microstructure and Mechanical Properties of In Situ Al-5 wt.% TiB2 Composite Fabricated by Stir Casting

Effect of Addition of Cerium Oxide, Cryolite, and Zirconium on Microstructure and Mechanical Properties of In Situ Al-5 wt.% TiB2 Composite Fabricated by Stir Casting