Commercial Purity Aluminum Research Articles

Characterization of L12-Al3Ce phase and its purification mechanism in the Al-Ce-TiCN alloy

Rare earth element Ce has a positive purifying effect on Fe and Si impurities in pure aluminum. In this study, we unveiled the mechanism of Ce purification of Fe and Si impurities in commercial pure aluminum at the atomic scale via utilizing the properties of TiCN nanoparticles, which exhibit distribution along grain boundaries and impede solute atom diffusion at specific cooling rates. The transition phase L12-Al3Ce was characterized in aluminum, which is considered to be an important transition phase to purified products. Furthermore, High Angle Dark Field Scanning Transmission Electron Microscopy (HADDF-STEM) and 3D Atom Probe Tomography (3D-APT) results showed that Ce could respectively enrich the Fe and Si impurities, resulting in the formation of Al-Ce-Fe and Al-Ce-Si clusters. Density functional theory (DFT) results indicated that Fe and Si atoms can incorporate into L12-Al3Ce crystal, forming more stable structures and therefore giving rise to the formation of Al-Ce-Si and Al-Ce-Fe nanoclusters. This study provides atomic-scale insights into the mechanism of Ce purifying Fe and Si impurities in aluminum.

Microstructure and performance of joint of Al/Cu welded by resistance element welding with an auxiliary gasket

A 1060 commercial-purity aluminum and T2 pure copper plates with a thickness of 2 mm were welded by using resistance element welding with an aluminum rivet and auxiliary gasket. The interfacial microstructure was analyzed, and the tensile shear load of the joint was tested. In the joint welded, a layer of Al2Cu adjacent to the copper and the eutectic structure of Al2Cu + (Al) near the nugget region were formed at the interface of Al/Cu. The tensile shear load of the joint increased first and then decreased with the increase of welding current, and it reached the maximum of 2.24 kN when the welding current was 26 kA. The results reveal that the application of the auxiliary gasket not only promote the thickening of the nugget, but also achieve the joining between the rivet leg and the upper plate when resistance element welding of Al/Cu is performed.

Effect of heat treatment before fast multiple rotation rolling on friction surfaced Al–Si–Cu alloy

In this study the effect of combination of heat treatment of consumable rod and solid solution heat treatment before fast multiple rotation rolling (FMRR) processing on microstructure, mechanical property and wear resistance of Al–Si–Cu alloy friction surfaced on commercial pure aluminum alloy were investigated. Results show that after the FMRR process, there is a significant reduction (99% reduction) in the friction surfaced coating surface roughness. The surface roughness after FMRR processing in the coatings created by homogenized and solid solution treated consumable rod is 0.74 ± 0.12, and 0.56 ± 0.08 μm, respectively. In the coating created by homogenized rod the minimum grain size (1.7 ± 0.2 μm) formed in the FMRR processed layer. Using homogenized consumable rod and FMRR processing by rotational speed of 3000 rpm and traverse speed of 140 mm/min, the maximum hardness (9.8 ± 0.3 GPa) and minimum wear rate (4.6 ± 0.1 μg/m) created at processed layer. FMRR processing by rotational speed of 3000 rpm and traverse speed of 140 mm/min, result in 27 and 24 % increasing in hardness at friction surfaced coating created by homogenized and solid solution treated consumable rods, respectively.

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

Effect of Al–Ti–B master alloy on microstructure and properties of aluminum-air battery anode materials

This study investigates the effects of Al–5Ti–B master alloy addition on the electrochemical properties and discharge performance of commercial pure aluminum (1060Al) in 4 M NaOH solution. The results show that the coarse branch-like α-Al grains are transformed into finer and smaller equiaxed grains, and the iron-rich phase are changed from long rod-like to small spherical grains. TiB2 particles introduce more heterogeneous nucleation sites in the α-Al crystals, resulting in an increased amount of grain boundaries in the aluminum matrix. There are more crystal defects at the grain boundaries than in the interior of α-Al grains, which provids more channels and energy for the reactions. This significantly increases the electrochemical activity of the aluminum alloy, causing the negative shifts for both the open circuit potential and the corrosion potential. The reduction in the size and change in the morphology of the iron-rich phase decreased the contact area between the iron-rich phase and the aluminum matrix, weakening the galvanic action between them. Meanwhile, the refinement of the α-Al grains decreased the potential difference between the interior and exterior of the grains, resulting in a reduction in the material corrosion current and an improvement in its corrosion resistance. Therefore, compared to the method of adding high hydrogen evolution potential elements to suppress hydrogen evolution reaction, the refinement of α-Al grains and the changes in the size and morphology of iron-rich phases due to the presence of TiB2 particles are the main reasons for improving the corrosion resistance and discharge performance of aluminum-air batteries in NaOH solution.

Grain refinement of aluminium welds by Ti, TiB_2, and TiC filler wire inoculation

A fine-grained fusion zone characterises a tough aluminium weld. To improve the solidification characteristics and refine the grains in aluminium welding, different inoculation particle combinations were introduced to the filler wire by solid state metal screw extrusion. Filler wires were I-joint welded with two different welding methods to reveal the potency for grain refinement. Grain size, microstructure, porosity content, and hardness across the weld was revealed. Gas metal arc welding with a Ti-TiC inoculated filler wire exhibited a remarkable grain refinement of 91% compared to a base reference of commercial pure aluminium. The Al_3Ti intermetallic phase was found as nucleation point. Gas tungsten arc welding showed lower grain refinement potency, and no Al_3Ti phase was found in any weld. Thus, the effect of welding method must be taken into consideration upon development of inoculant containing filler wires.

Strengthening mechanisms of a heterostructured pure aluminum with extraordinary mechanical properties

To achieve superior mechanical properties in metallic materials, one promising way is to make them into heterogeneous structures (HS). In this work, a novel HS including grain size and dislocation density is developed in commercial pure aluminum through cold-rolling and subsequent partial annealing processes. Tensile tests show that the HS specimen, annealed at 150 °C for 2 min with ~31.1% recrystallized grains, have a high yield strength of ~121 MPa and a good uniform elongation of ~8.5%. The yield strength increases by 10% and the ductility increases by 7 times compared with the as-rolled specimen, respectively. Detailed microstructure characterizations confirm that a significant strain gradient was generated near the interface between the hard zone and soft zone, in which the slip and plugging of geometrically necessary dislocations act as an important role in the abnormal hardening and strengthening phenomena of the HS specimen. To quantify the specific contribution of each strengthening mechanism, we compare the experimental measurements with the theoretical calculations and confirm that the multiple deformation modes are activated by the deformation stress. The hetero-deformation-induced hardening and strengthening effects are responsible for the superior mechanical properties of the heterostructured pure aluminum.

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

This study presents that A1050 commercial-purity aluminum increases the tensile strength and ductility using the processes of accumulative roll bonding (ARB) and high-pressure sliding (HPS). Both processes yield a similar tensile strength exceeding 240 MPa after processing by ARB for 10 cycles and by HPS for the sliding distance of 15 mm, respectively. The stress-strain behavior is evaluated through microstructure observations and measurements of strain hardening rates. Significant grain refinement with well-defined grain boundaries is responsible for the strength increase. The grain refinement also leads to an increase in strain hardening rate and thus an increase in the ductility.

Experimental and numerical investigation of Al[sbnd]16Si alloy friction surfacing on AA1050 aluminum substrate: Effect of axial feeding rate

Using the smoothed-particle hydrodynamics (SPH) simulation method and experimental investigation, this study evaluated the effect of consumable rod axial feeding rate on microstructure, mechanical properties, and wear resistance of coatings during the friction surfacing process of an AlSi alloy containing 16.6 wt% silicon on a commercial grade pure aluminum substrate. The interaction of coating and substrate at the interface was investigated using the thermomechanical simulation. According to simulation and experimental results, by increasing the axial feeding rate from 100 to 150 mm/min, the average deposition efficiency has increased from 36 to 43 %. The predicted results achieved from smoothed-particle hydrodynamics simulation show that by increasing the axial feeding rate from 100 to 150 mm/min, the shear stress at the coating/substrate interface increases from 86 ± 4 to 112 ± 6 MPa. By considering the average velocity at the interface, the simulation predicted the roughness with high precision. By increasing the axial feeding rate from 100 to 150 mm/min, interface roughness decreased from 105.2 ± 29.7 to 83.2 ± 26.9 μm. Compared to the pure aluminum substrate, surfacing with an AlSi alloy containing 16.6 wt% silicon results in minimum/maximum hardness and wear resistance increases by 212 / 265 % and 57 / 60 %, respectively.

Multiple effects of forced cooling on joint quality in coolant-assisted friction stir welding

To understand the multiple effects of forced cooling on the joint quality in coolant-assisted friction stir welding and the underlying mechanism, commercial pure aluminum AA1050 was welded by liquid–CO2–assisted friction stir welding (FSW) within a large process parameter range. The cooling effects on the weld formation, microstructure, and mechanical properties were investigated by comparison with conventional FSW. The microstructure evolution during the liquid–CO2–assisted FSW process was revealed by EBSD characterization together with thermal cycle measurement and short-time annealing. The results show that the process parameter window was narrowed by the liquid CO2 cooling. Forced cooling led to weld surface grooves and interior cavities under “too cold” welding conditions. The grains in the weld zone were refined and the areas of the weld cross-section were reduced by the forced cooling, resulting in the tensile strength of the joint being improved but the elongation being reduced. The thermal cycle shows that the liquid CO2 cooling compressed the welding temperature field by decreasing the heating rate and increasing the cooling rate, giving rise to the decrease in deformation temperature at the stirring stage. The low deformation temperature promotes dynamic recrystallization by changing the way of recrystallization and thus refines the grains. Further, the liquid CO2 cooling suppresses the grain growth which should have happened in natural cooling. Combining the above two aspects, the grain in the weld zone was refined and the tensile properties of the joints were changed. Nevertheless, the contribution of decreasing the deformation temperature to the grain refinement is more significant than that of increasing the cooling rate.

Evolution Behavior of the Surface Oxide Film of Al Alloy Scraps in the Melt

The oxide film on the scrap surface is one of the primary sources of oxide inclusions in the aluminum melt. Understanding the evolution of the oxide films in the aluminum melt is an important step for developing efficient recycling technologies and controlling the quality of the product. In the present study, we studied the evolution behavior of the oxide film in the aluminum melt. The oxide films were introduced via aluminum alloy scraps into the melt, and the micro-morphology and composition of the oxide film were analyzed by scanning electron microscope and energy spectrum. Results show that the oxide film on the surface of 1235 alloy foil, A356 alloy turning, and 5083 alloy scalping were broken into small flake oxide film and then transformed into minor granular oxide when the scraps were charged into commercial purity aluminum melt. However, in aluminum alloy melt containing magnesium, the oxide film remained an intact sheet shape up to a certain melt dwelling time.

Numerical Study and Experimental Verification on Solidification Characteristics in Commercial Purity Aluminum under Mechanical Vibration

Numerical Study and Experimental Verification on Solidification Characteristics in Commercial Purity Aluminum under Mechanical Vibration

Cladding and Natural Aging of Aluminium Alloy 2024 for Aircraft Application

Aluminium alloy 2024 is widely used in the manufacturing of aircraft components such as skin panels for the wing. Generally, the aluminium alloy 2024 is delivered as cold work condition i.e., 2024 T3. However, the aluminium alloy 2024 T3 does not meet the standard for aircraft wing skin. Therefore, further treatments such as cladding and heat treatment are carried out to improve its quality. Cladding was introduced to the 2024 T3 alloy at 495 °C using commercial purity aluminium. Subsequently, T42 heat treatment was introduced to the 2024 T3 alloy at 500 °C for 40 minutes, then followed by quenching and natural aging for 96 hours, yielding 2024 T42 aluminium alloy with cladding (T42 Clad). 2024 T42 aluminium alloy without cladding (T42 Bare) was also obtained by T42 heat treatment of 2024 T3. The effect of cladding and natural aging on mechanical properties is investigated by tensile test and hardness test. Conductivity meter was used to determine the electrical conductivity. Intergranular corrosion test and stress corrosion crack test were performed to investigate the effect of cladding and natural aging on corrosion resistance. Results indicate that the solution treatment and natural aging improve corrosion resistance, mechanical properties, but reduce electrical conductivity values. Cladding gives higher electrical conductivity value and elongation. Both natural aging and cladding treatment provide appropriate aluminium alloy for aircraft wing skins.

Failure mechanism during incremental sheet forming of a commercial purity aluminum alloy

Incremental sheet forming (ISF) is known for many advantages over conventional forming, such as part flexibility, low tooling cost and higher formability. Previously various studies have explored the failure mechanism experimentally and numerically. However, limited studies have been performed on the micro-mechanics of failure during ISF process. This study involves failure mechanism during incremental sheet forming of a commercial purity aluminum alloy (AA1050). During experiments, failure (fracture) was observed in truncated cone specimens by increasing the wall angle from 71° to 72°. The mechanism behind failure was explored with detailed microstructural characterization and finite element (FE) simulations. Various samples were taken from the successfully formed and failed cones for microstructural analysis. The electron backscatter diffraction (EBSD) based microtexture measurements associate this failure with more grain fragmentation and necking or localized deformation in the failed cone. Further, the X-ray diffraction (XRD) based residual stress measurements indicate high positive (tensile) hydrostatic stresses (∼157 MPa) on the outer surface of the failed (fractured) cones. Finite element analysis (FEA) with Gurson-Tvergaard-Needleman (GTN) damage model was used for fracture prediction. The FEA results also support the residual hydrostatic stress evolution in the cones, albeit at a slightly different wall angle. Based on microstructural and finite element analysis it is concluded that deformation becomes inhomogeneous when the failure occurs during ISF process.

Dissimilar diffusion bonding of bulk metallic glass: Amorphous/crystalline atomic-scale interaction

Dissimilar diffusion welding of a copper-based bulk metallic glass (BMG) with a stoichiometry of Cu 50 Zr 43 Al 7 and commercial pure aluminum was performed at evaluated different temperatures (below and higher than the glass transition temperature ~ 440 °C) and holding times (up to one hour). The main goal was to successfully bond these dissimilar materials without crystallizing the BMG part to avoid deteriorating properties. Optimum joining conditions were attained at a temperature of 430 °C (<T g ) and dwell time of 60 min. The diffusion-assisted atomic-scale interactions between the amorphous and crystalline structures were studied using electron microscopy. To this end, the interaction zone at the BMG/Al dissimilar interface was extracted and analyzed by focused ion beam/transmission electron microscopy (FIB/TEM) followed by elemental analysis and high resolution-transmission electron microscopy (HR-TEM) to reveal the nature of the diffused layer and orientation relationships within the structure. Based on microscopy observations, the formation of an interaction layer with a thickness in the range of 1–2 μm was observed, confirmed by diffusion of oxygen to this region. High-resolution atomic-scale observations supposed a gradient transition from crystallinity toward the amorphous state undergoing the formation of some semi-crystalline nano-scale layers. The activation energy for the thermally-assisted diffusion bonding process was estimated at ~486.7 kJ/mol, related to the substitutional diffusion of oxygen through the copper matrix after decomposition of the stable alumina oxide layer on the surface. Accordingly, an increased indentation hardness across the dissimilar interface was observed and attributed to the distribution of elements into the reaction layer and the formation of new phases. • Atomic-scale diffusion bonding of Cu-based BMG to Al was studied by FIB-TEM analysis. • Elemental inter-diffusion in amorphous-crystalline materials interaction characterized. • Decomposition of oxide surface layer and formation of a semi-crystalline phase at the interface associated bonding. • A gradual atomic structure transition from amorphous to crystallinity was revealed across the interface. • The activation energy of the bonding process was estimated at ~486.7 kJ/mol, nearby to substitutional diffusion of oxygen.

Microstructure and corrosion resistance of commercial purity aluminum sheet manufactured by continuous casting direct rolling after ultrasonic melt pre-treatment

During the new continuous casting direct rolling (CCDR) process for manufacturing commercially pure aluminum sheet for foils, casting defects tend to arise as the raw material with huge mass flow rapidly solidifies under a high cooling rate, which generates negative effects on the formability of aluminum sheets and the performance of final foil products. Therefore, melt pre-treatment during continuous casting is very essential to improve the quality of the billet. In this study, multi-source ultrasonic field was employed to pretreat an Al melt during the continuous casting stage in a Hazelett CCDR strip production line. The Ti content distribution in the melt, the microstructure and corrosion behaviors of the rolled sheet with and without ultrasonic melt pre-treatment (UMPT) were investigated. The microstructure of the rolled sheet was refined due to the increased Ti content and uniformly distributed Al3Ti particles under UMPT. In addition, the morphology of the Fe-containing secondary phase was modified from an aggregated to a scattered structure, with reduced continuity. As a result, under the combined effects of the refined α-Al grains and secondary phase, the corrosion resistance of the rolled sheet was improved. The underlying mechanisms for the modifications of the microstructure and corrosion resistance after UMPT are also interpreted, which gives theoretical guidance on the practical applications of the ultrasound-assisted continuous casting in industrial production.

Hydrostatic twist extrusion (HTE) for processing relatively long ultrafine grained samples

In this study, hydrostatic twist extrusion (HTE) has been introduced for processing relatively long ultrafine grained (UFG) bulk samples. By using high-pressure fluid surrounded the sample, surface contact between die and sample was eliminated. The high-pressure fluid causes high hydrostatic pressure, which leads to improvement of material properties and increased the aspect ratio of the sample (length/diameter). The HTE process was applied to commercial pure aluminum samples at room temperature, and then microstructure and mechanical properties were examined. The results demonstrate that after HTE process, the grain size was reduced from 54 µm to ∼800 nm, and microhardness was increased from 29.2 HV to 37.7 HV. Also, yield and ultimate strength were noticeably increased from 78 MPa and 103 MPa to 166 MPa and 175 MPa, respectively. This process seems to be very promising and interesting for the future industrial application.

Development of Wear Resistant Aluminum Based Nano-Composite Reinforced With Nano-AlN

Abstract The present study aims at development of nano-AlN reinforced aluminum metal matrix composite through stir casting method. For this commercially pure aluminum (CP-Al) and CP-Al + 2 wt% AlN nano-composite were casted at 760 °C by stir casting method. Both the alloy and the composite were subsequently characterized using optical microscopy and scanning electron microscopy. They were further tested for mechanical properties and dry sliding pin-on-disk wear studies were carried out at three different loads at room temperature at 200 rpm up to a sliding distance of 2 Km. The results indicate good particle dispersion into the matrix and massive grain refinement in the nano-composite. Accordingly, there is an improvement in UTS and 0.2% YS values by more than 100% by keeping ductility unaffected in the composite compared to the base alloy. Grain refinement and strengthening effect of nano-particles are the reasons for this improvement. Moreover, the wear study reflects considerable improvement in wear resistance in the composite at all loads. Suppression of adhesion (at all loads) and plowing abrasion (at 60 N load) are attributed to this improvement in wear resistance in the composite.

Design of newly effective grain refiner for aluminum based on medium-entropy metal diboride

In this paper, medium-entropy metal diboride (Ti1/3Cr1/3V1/3)B2 with a hexagonal TiB2-type crystal structure were synthesized via molten salt reaction, and its effect on refining pure aluminum grains was investigated. Compared with TiB2, the minimum lattice mismatch between Al and (Ti1/3Cr1/3V1/3)B2 is reduced from 5.6% to 3.7%, effectively reducing undercooling required for nucleation. By just adding 1.5 vol% (Ti1/3Cr1/3V1/3)B2, the average grain size of commercial pure aluminum is reduced to ∼32 μm. The synthesized particles are expected to be used in grain refinement during additive manufacturing and rapid solidification, and in the preparation of aluminum matrix composites. This study opens up a new direction in designing new compounds for grain refinement by tailoring lattice matching within multi-component composition space.

Tag-and-Trace Method of α-Al Crystals Applied to Study Solidification and Casting of Aluminum Alloys

In this study, a new tag-and-trace method of α-Al crystals was developed and used to study the dissolution of a rotating Al-3Si-0.15Ti cylinder immersed into a superheated commercial purity aluminum melt. The developed tag-and-trace method consists of tagging the primary crystals of an alloy with the microsegregation of a peritectic forming solute element, e.g., titanium in aluminum alloys. During solidification, the primary crystals form with a high concentration of the peritectic forming solute, decreasing in the adjacent growth regions of the same crystal. After solidification, the solute microsegregation tag in the interior of the primary crystals can be revealed by color etching. In this work, an Al-3Si-0.15Ti cylinder with all the primary α-Al crystals tagged with titanium was immersed into a superheated titanium-free aluminum alloy. The superheat was varied, and all samples were quenched 10s after immersion of the cylinder. The tagged α-Al crystals from the original cylinder could be distinguished from the non-tagged α-Al crystals formed in the thermally undercooled region surrounding the cylinder and during quenching. Indications of liquid penetration were observed in some α-Al crystals, which indicates that disintegration of α-Al crystals may occur during stirring of the alloy cylinder into a superheated alloy.