bluuebunny/crossref_metadata_2025 huggingface dataset:
Cast Al-Si-Cu Alloys: Effect of Modification on Thermal and Electrical Conductivities
Authors: Huitrón Carlos , Valdés Eduardo , Valtierra Salvador , Colás Rafael
Published: February 2019

The effect that modification of cast Al-Si alloys exerts on the thermal and electrical conductivities is presented. The work was conducted by casting a series of samples in a rig that promotes unidirectional solidification to vary the level of microstructure refining, which was assessed by the secondary dendrite arm spacing. The alloys were prepared in a furnace and poured into the rig after adding different amounts of strontium to modify the aspect of the aluminum-silicon eutectic. Measurements were conducted on as-cast and heat-treated specimens. The electrical conductivity tests were referred to the International Annealed Copper Standard. Thermal conductivity of the different samples was obtained by comparing it with that of a high-purity aluminum sample. It was found that either value of conductivity depends on the degree of modification and by heat treating, whereas other microstructural parameters exert a secondary effect.
Recycling of EN AW 2011 Aluminum Chips without Remelting
Authors: Lela Branimir , Krolo Jure
Published: February 2019

This article deals with the direct recycling of EN AW 2011 aluminum alloy chips, which are formed by turning, into semifinished products using forward hot extrusion process. Direct recycling without re-melting is usually called solid-state recycling. The main aim of this article is to investigate the influence of depth of cut (size of chips) in the aluminum alloy turning process, extrusion temperature, and compaction force on mechanical properties, surface roughness, and extrusion force of recycled samples. An original approach to solve this problem is mathematical modelling of the process using the design of experiments. The influence of main research factors on yield strength (Rp0,2), hardness (HV), extrusion force (F), and surface roughness (Ra) of recycled samples has been studied. The study has shown that the most influential factor on mechanical properties, surface roughness, and extrusion force was extrusion temperature.
Strain Rate Sensitivity of Commercial Aluminum Alloys
Authors: Picu R.C.
Published: February 2019

This article presents a review of the strain rate-dependent mechanical behavior of aluminum and its commercial alloys. The importance of strain rate sensitivity (SRS) stems from its relation with ductility and formability. Plastic deformation is stable and localization less likely in alloys with higher SRS. After discussing the basic formulation used to interpret experimental data, the methods used to measure the SRS parameter are presented. This is followed by a brief review of the main mechanisms that render the flow stress sensitive to the deformation rate, including mechanisms leading to positive and negative SRS. The generic dependence of the SRS parameter on the strain, temperature, and strain rate are further presented using data for pure Al. The effect of alloying is analyzed in the context of solid solutions and precipitated commercial alloys. Results on solid solutions are discussed separately at low and elevated temperatures in order to evidence the role of solute diffusion on SRS. This article ends with a brief discussion of the grain size dependence of SRS, with emphasis on recent efforts to produce nanocrystalline and ultrafine-grained materials by severe plastic deformation.
Aircraft Structural Integrity: Corrosion Effects
Authors: Crawford Bruce , Loader Chris , Harrison Timothy J.
Published: February 2019

Corrosion damage can significantly reduce the structural integrity of aluminum alloy components in aircraft. This is a serious threat to the airworthiness of aircraft which means that corrosion prevention and repair are a major cost to aircraft operators. This article details a practical approach to the management of corrosion in aircraft by describing the forms of corrosion that are common in aircraft, the detection and measurement of these forms, and how they affect the airworthiness of aircraft designed using the dominant airworthiness philosophies. It concludes with a brief outline of how the structural integrity effects of each type are modeled.
Thin Aluminum Sheets: Continuous Casting and Rolling
Authors: Peter Ildiko , Rosso Mario
Published: February 2019

This article provides a short history and presents the state of the art of continuous casting and rolling of aluminum and its alloys, currently used for the production of Al alloy sheets for different applications. Some fundamental aspects related to this technology are integrated with experimental results obtained by the authors during the years spent studying the development of grain structure and the effect of homogenization treatment and rolling on the microstructural evolution of Al sheets.
Calcium-Containing Aluminum Alloys
Authors: Akopyan Torgom , Belov Nikolay , Naumova Evgenia
Published: February 2019

The phase composition and microstructure of ternary alloys, Al–Ca–X (where X = (Silicon) Si, (Magnesium) Mg, (Zinc) Zn, (Copper) Cu, (Nickel) Ni, (Iron) Fe, (Manganese) Mn, and (Scandium) Sc), developed based on Ca-containing eutectics have been studied. In most systems, ternary compounds are detected. It is found that the structure of Ca-containing eutectics is much finer than that of Al–Si alloys. Such alloys have a good combination of technological properties during casting and deforming. Because of the high volume fraction of Ca-containing particles (up to 33 vol.%), they may be considered as promising “natural composites.” The strength properties of Al–Ca–X alloys may be significantly enhanced by adding Sc and Zr, forming L12 nanoparticles. Alloys of the system Al–Zn–Mg–Ca can reach hardnesses higher than 200 HB, which gives reason to expect good strength properties. With the example of the Al–9%Zn–3.5%Mg–3%Ca model experimental alloy based on the (Al) + (Al,Zn)4Ca eutectic, the possibility, in principle, of manufacturing rolled sheets has been demonstrated.
Pulsed TIG Welding of Al–SiC Composite: Welding Parameter Optimization
Authors: Sivachidambaram P. , Srinivasan Raghuraman , Ramamoorthy Venkatraman
Published: February 2019

Pulse on time, pulse frequency, peak current, and base current are the important parameters to be optimized in pulsed current tungsten inert gas (PCTIG) welding of Al–SiC metal matrix composite. Experiments were designed and conducted using the L9 orthogonal array technique. The regression equation was developed using Design Expert® statistical software package to predict the weld center’s micro hardness, yield strength, ultimate strength, elongation (%), bending load, weld depth, weld width, cooling rate, and peak temperature near the weld zone of Al-8% SiC composite, welded using PCTIG welding. Correlation coefficient shows 0.9 for all the mechanical properties. This showed that the regression equation and the mathematical model developed were adequate. Analysis of contour plot, interaction effect, signal-to-noise ratio, and mean response were developed, the influence of each pulsed current parameter was evaluated at each level, and the percentage of influence was calculated by using pulsed current parameters. Ultimate tensile strength and bending load values depend on the microstructure. When the cooling rate is higher, fine microstructures are observed due to grain refinement; higher tensile strength and bending load are also observed. Due to the decreased cooling rate, coarse microstructures are observed, which result in poor tensile strength and bending load. PCTIG welding parameters are responsible for the change in the cooling rate of the weld zone. The optimization of the PCTIG welding parameters shows that the peak current and base current should be 160 and 60 A, respectively. Pulse on time is recommended to be 50%–55% and pulse frequency to be 5 Hz.
High-Pressure Die-Cast AlSi9Cu3(Fe) Alloys: Models for Casting Defects and Mechanical Properties
Authors: Timelli Giulio
Published: February 2019

The effect of casting defects on the tensile properties of high-pressure die-cast AlSi9Cu3(Fe) alloys is reported. A series of U-shaped structural components has been die-cast using a combination of injection parameters and pouring temperatures in order to produce different types and amount of casting defects throughout the casting. The results reveal how the die-castings contain defects, primarily pores and oxides, and their presence and distribution are highly sensitive to the process conditions. The tensile properties are affected by the amount and distribution of defects and can be determined by the defect area fraction. The influence of casting defects on the tensile properties are investigated through a theoretical verification based both on constitutive and stochastic models. The analytical approach, based on the Ghosh constitutive model of tension instability, correctly indicates the trends of the experimental results, while the Weibull statistics evidences how the scale parameter and the Weibull modulus are strongly affected by the casting conditions.
Honeycomb Composite Structures of Aluminum: Aerospace Applications
Authors: Majid D.L. , Manan Nor Hafizah , Chok Yee Ling
Published: February 2019

A honeycomb composite structure is usually composed of a lightweight hexagonal core sandwiched between two thin face sheets that are adhesively joined. Both the core and the face sheets can be combinations of many types of materials depending on the application. In this article, an overview of the design and manufacturing process of aluminum honeycomb composite structures particularly for aerospace application is presented. Aluminum honeycomb composite structures are lightweight constructions with high specific strength and stiffness that are applied mainly in the aerospace industry. An aluminum honeycomb panel is typically made up of the secondary structural components and interiors of an aircraft such as the wing skin, trailing edge, control surface, flooring, partitions, aircraft galleys, and overhead bins, to name a few. Other applications are in the spacecraft, helicopter, missile, and satellite. Owing to its honeycomb design peculiar to the hexagonal beehives, it can reach more than 30 times higher in stiffness and 10 times higher in flexural strength compared to its solid counterpart of the same weight. The mechanical properties of the honeycomb composite structure hinge on the materials of the core and face sheets, the core geometries, and the thickness of the face sheets. Designed for superior flexural and shear loading, the selection of the optimal honeycomb design will depend on the application requirements. The principal design criterion of a sandwich structure in aerospace applications is weight saving, and there is a trade-off between performance and cost. In terms of manufacturing of the honeycomb composite sandwich structure, the two main processes are the expansion process commonly used for low-density cores and the corrugation process for higher density cores.
Nodular Silicon Al–(12–30)% Si Alloys: Microstructure, Mechanical Properties and Fracture Behaviors
Authors: Wang Ruyao , Lu Wei Hua
Published: February 2019

The microstructure, mechanical properties, and fracture of nodular silicon hypereutectic Al–Si alloys containing 12–30 wt% Si are discussed. The eutectic and primary silicon particles are nodulized, offering an average aspect ratio of 1.60–1.70 with a designed modification practice followed by a solution heat treatment of 8–10 h at 510°C–520°C. Such a soaking temperature does not result in coarsening or clustering of the silicon particles. Nodulization of silicon phase leads to an increase in the tensile strength and ductility of alloys at room and elevated temperatures compared with commercial Al–Si alloys. Increasing the Si content leads the tensile strength and elongation of alloys at room temperature to fall down due to the formation of coarsen primary Si grains, but the ultimate tensile strength at 300°C remains unchanged. The ultimate tensile strength σb-alloy of hypereutectic Al–Si alloys is inversely proportional to square root of maximum silicon size dmax. The initiation and propagation of the crack with continuous increase in applied loading were observed under scanning electron microscope. The fracture surfaces in nodular silicon Al–Si alloys are composed of equiaxed ductile dimples. The finite-element method has been used to study the stress distribution within the different morphologies of Si grain and how Si and Al phases interact during loading.
Melt-Stirring Method: Influence on Ingot Purity During Ohno Continuous Casting
Authors: Fashu Simbarashe , Mudzingwa Lynette , Mukuya Aaron , Tozvireva Macdonald , Khan Rajwali
Published: February 2019

This article outlines the findings in the comparison of the influence of mechanical and electromagnetic stirring (EMS) on ingot long-term purity and uniformity during Ohno continuous casting (OCC). The magnitude of the average optimum velocity flow field and stirring parameters required to effectively purify aluminum ingots using mechanical stirring of the melt was determined and analyzed. Basing on the determined optimum mechanical flow field, electromagnetic parameters producing almost the same flow field near the interface were obtained through careful adjustments of parameters. Optimum parameters of the mechanical and EMS were obtained by numerically solving the solidification model coupled with either the multi-reference frame model (for mechanical stirring) or the magnetohydrodynamic model (for EMS) in CFD Fluent 6.3.26 software. For mechanical stirring, an optimum stirring intensity of 2 mm/min was determined whilst for EMS, the optimum magnetic field with an amplitude of 20 mT and a frequency of 2.7 Hz was determined, and these produced same magnitude optimum flow fields resulting in high-purity aluminum ingots. Comparison of the two methods showed that EMS is good in covering all the regions near the solid–liquid interface and is more effective in bulk melt mixing; thus it produces more uniform and purer ingots for longer casting times.
Reaction Kinetics during Molten Aluminum Refining Using Electron Backscatter Diffraction
Authors: Flores Valdés Alfredo , Torres Jesús , Ochoa Rocío
Published: February 2019

Using the novel technique of electron backscattered diffraction (EBSD) in the scanning electron microscope, this article presents a comprehensive study on reaction kinetics during molten aluminum refining, applied to the removal of antimony using calcium additions and magnesium removal using silica additions. The determination of reaction products using the EBSD technique permitted to define stoichiometry of reactions taking place, as well as the clarification of the reaction mechanisms occurring during refining. Therefore, the kinetic parameters of interest such as rate constant values and activation energy of each process are obtained.
Quench Sensitivity and Continuous Cooling Precipitation Diagrams
Authors: Kessler Olaf , Milkereit Benjamin , Schick Christoph
Published: February 2019

The application properties of metallic materials are frequently adjusted by heat treatments utilizing controlled microstructural changes—i.e., solid–solid phase transformations like nondiffusional martensitic transformation or diffusional secondary phase precipitation and/or dissolution. For technical application, knowledge about the characteristic temperatures and times but moreover about their time dependence (kinetics) is required. As the relevant solid–solid phase transformations all show a heat effect (e.g., precipitation → exothermic; dissolution → endothermic), one outstanding measurement technique to follow these phase transformations is calorimetry, particularly differential scanning calorimetry (DSC). Appropriate combinations of DSC methods and devices to cover nine orders of magnitude in heating and cooling rates (10−4–105 K/s) will be introduced, using dissolution and precipitation reactions in aluminum alloys as examples. Basically, these techniques allow one to record time–temperature transformation (or precipitation/dissolution) diagrams for various materials during heating, isothermal annealing, and even during continuous cooling, making DSC a very powerful tool for the investigation of solid–solid phase transformations. Nowadays, physically based models verified with DSC results moreover allow one to predict precipitation volume fractions and solute mass fractions.
Weldable Aluminum Alloys in Aerospace and Transportation
Authors: Sverdlin Alexey
Published: February 2019

Fabrication of high-strength aluminum alloys with the application of welding is one of the most important directions for increasing efficiency and performance characteristics of the aircraft. Today, the aerospace industry has accumulated extensive experience in the application of welded aluminum alloys. Of course, the individual structural elements are made of steel, titanium alloys, or composite materials, which increase the reliability and functionality of the designs in general.
Hot Tear Nucleation During Solidification of Aluminum and Its Alloys
Authors: Tiryakioğlu Murat , Yousefian Pedram
Published: February 2019

This article presents a discussion of hot tear formation by first re-interpreting tensile test experimental results for aluminum castings in the literature. Based on the previous findings that a pore should first nucleate to result in a hot tear, the physics of pore formation is reviewed through theoretical fracture pressure calculations. Theoretical fracture pressure of liquid aluminum was calculated to be approximately −3.5 GPa, which is 4 orders of magnitude higher than the tensile strength data reported in the literature. Further calculations showed that it was impossible for a pore to nucleate either homogeneously or heterogeneously in liquid aluminum. The formation of pores and hot tears in aluminum castings can only be explained by inflation of entrained surface oxide films (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with tensile test results in the literature as well as physics principles.
Surface Modification of Aluminum and Its Alloys Using Conversion Coatings
Authors: Anicai L. , Visan Teodor
Published: February 2019

This article presents some information related to the chemical conversion procedures applied onto Al and its alloys involving both classical hexavalent chromium-based solutions and the most recent ones involving transitional metals and/or rare earth compounds, as environmentally friendly alternatives. The main characteristics of the formed thin films, including appearance, composition, morphology, corrosion resistance, and performance, are also presented.
Hypoeutectic Al–Fe Alloys: Formation and Characterization of Intermetallics by Dissolution of the Al Matrix
Authors: Garcia Amauri , Goulart Pedro , Bertelli Felipe , Spinelli José , Cheung Noé
Published: February 2019

A careful technique of dissolution of the Al-rich phase is conducted in hypoeutectic Al–Fe alloys samples, which were solidified under a wide range of cooling rates envisaging deeper investigations on the skeletal arrangement of either Al6Fe intermetallic fibers or Al3Fe plates, and their dependence on solidification thermal parameters. The experiments were carried out with hypoeutectic Al–Fe alloys, subjected to equilibrium solidification from the melt, steady-state solidification (Bridgman growth), transient directional solidification in water-cooled and air-cooled molds and rapid solidification (laser remelting), thus permitting a significant range of microstructural scales to be examined. It is shown that Al6Fe prevails for cooling rates >1.5 K/s, and that a short zone of coexistence of Al3Fe and Al6Fe phases exists for cooling rates <1.5 K/s, which is rapidly replaced with the prevalence of Al3Fe intermetallics with further decrease in cooling rate. In contrast, even with high values of cooling rate, typical of the laser remelting process, the Al–Al3Fe eutectic is shown to prevail.
Field Trials of Aerospace Fasteners in Mechanical and Structural Applications
Authors: Nadim Melhem George , Richard Munroe Paul , Christopher Sorrell Charles , Clyde Livingstone Alsten
Published: February 2019

The present work reports findings for the application of specialized aerospace aluminum rivets, manufactured from Al 7075 (Al-Zn-Mg-Cu) T6 alloy stem/mandrel, with an Al 5056 (Al-Mg) shank or sleeve, which were used for construction rectification of an outdoor louver façade on a high-rise building. These specialized rivets were used to replace failed conventional construction rivets, which consisted of sleeve and mandrel comprised of either all-steel, all-aluminum, or aluminum-steel. The building is in close vicinity to the ocean and exposed to extremely high wind loading, making the rivets susceptible to failure by corrosion and fatigue. The focus of the present work is to report the examination of the specialized replacement rivets following an in-service lifetime of 12 years. The examination revealed that the replacement rivets (mandrel and sleeve) remained intact and uncontaminated, essentially free of corrosion. It is likely that sunlight exposure and the composite nature of the rivets enhanced the performance through age hardening. Analysis of the rivets included visual inspection, optical microscopy, Vickers microhardness testing, and transmission electron microscopy. The aim of the analysis was to correlate microstructures with microhardnesses, using these data to evaluate the ultimate tensile strength (UTS), yield strength (YS), and the potential for further age hardening. The Vickers microhardnesses were observed to have increased by ~8% over the service lifetime of 12 years, which equates to increases in YS (34.8–46.8 MPa) and UTS (23.8–45.6 MPa). Although the results show that there is a large increase in the strength values when comparing the unused rivets to the 12-year-old rivets, this increase in hardness may not necessarily be due purely to natural aging kinetics such as exposure from the sun and outdoor temperature. However, there appears to be some insignificant alteration of the microstructure and mechanical properties as a result of this exposure.
Microstructural Evolution During Solution Treatment of ADC12 (A383) Alloy Die Castings
Authors: Yeom Gil-Yong , Eisaabadi Bozchaloei Ghasem , Lim Hyun-Kyu , Kim Shae Kwang , Yoon Young-Ok , Hyun Soong-Keun , Netto Nelson , Tiryakioğlu Murat
Published: February 2019

High-pressure die casting (HPDC) components are known to be not heat treatable due to the formation of unacceptable surface blisters, dimensional instability, and poor mechanical properties during conventional solution treatment, such as at 540°C for 8 h. In the present study, the possibility of solution treating a recycled ALDC12 HPDC alloy at temperatures less than 500°C and with shorter solution treatment times was investigated. HPDCs with thickness of 2 and 3 mm were solution treated at 490°C for various times ranging from 15 to 180 min. Microstructural evolution during solution treatment was examined by various techniques, including metallography, energy dispersive spectrometry, electrical conductivity, and X-ray diffraction. Results indicated that almost all of the Al2Cu intermetallics were dissolved within 90 min of solution treatment. The coarsening of eutectic Si particles was found to follow the Lifshitz–Slyozov–Wagner theory with two distinct regimes. Furthermore, measurements of Cu concentration within α-Al dendrites revealed that the diffusion of Cu atoms in α-Al phase is not the primary limiting factor for homogenization of the alloy. Most importantly, no blisters were observed at the surface of the castings. Therefore, this heat treatment can be used for HPDC components from ALDC12 alloy at a reasonable time.
Molten Aluminum: Inductive Technique for Electrical Conductivity Measurements
Authors: Bakhtiyarov Sayavur , Overfelt Ruel
Published: February 2019

A rotational, contactless inductive measurement technique has been used to determine the effect of pores and metallic insertions on the electrical resistivity of A2011 aluminum alloy at different temperatures. It is shown that the electrical resistivity increases with the total volume of pores and is also dependent on the pores locations and orientation. Additional energy losses were found on the contact surfaces between sample and insertions.
Diesel Engine: Applications of Aluminum Alloys
Authors: Pekguleryuz Mihriban , Ozbakir Erol , Farkoosh Amir Rezaei
Published: February 2019

The Diesel engine, introduced by Rudolph Diesel in 1892, achieves a higher combustion ratio and fuel efficiency, has lower CO2 emissions per mile than the gasoline engine and is considered to be one of the most viable environmentally friendly technologies for vehicles. “Clean Diesel” using lower sulfur content fuel has become available since 2006. Currently, the Diesel engine and cylinder head are mostly cast iron to withstand the high compression pressures and temperatures of Diesel operation. Further weight reduction (40%–55%) via aluminum substitution in the Diesel engine would result in substantial fuel economy and increased environmental benefits. Current aluminum alloys cannot meet the requirements of the Diesel engine and a new research topic has emerged in aluminum materials technology to address these requirements. The main issue with aluminum alloys is the low resistance to thermal fatigue that results from the constrained expansion and contraction of the material in the interval regions leading to compressive creep deformation at 300°C during engine heat-up and to tensile deformation around 150°C during engine cooldown. This article discusses the performance requirements and the design principles for aluminum alloys for Diesel engine applications. Efforts on the modification of A356 and A319 alloys via Cu, Mg, Ni, Cr, V, Zr, Ti, and Mn addition are reviewed. Recent studies on Mn/Mo addition are presented and the related principles are introduced in designing high volume fraction, thermally stable, and uniform nanoscale dispersoids using solutes with opposite partitioning coefficients in aluminum.
Quenching of Aluminum Alloys
Authors: da Silva Mattos Wellington , Rivolta Barbara , Totten George , Meekisho Lemmy , Canale Lauralice de Campos Franceschini
Published: February 2019

This article aims to describe the media, procedures, and techniques applied to quenching for heat treatment of aluminum alloys besides problems related to this specific process. This article presents important topics such as quench sensitivity, cooling curves analysis, showing experimental apparatus details, influence of probe format and comparison between probe types used in quenching, and problems related to surface oxidation due quenching. Polymer quenchants types are analyzed besides quenching parameters. There is a discussion related to surface rewetting and its importance for quenching successful. Different quenching process are presented like “uphill” process comparing as cryo quenching, ultrasonic agitation, and ionic liquids besides topics related to corrosion types and residual stress after quenching.
Quench Sensitivity of Aluminum Alloys
Authors: Rivolta Barbara , Gerosa R.
Published: February 2019

The demand of alloys with high strength-to-density ratio is continuously increasing in the engineering world. Beside very expensive materials, such as the titanium alloys and the high strength reinforced polymers, the aluminum alloys represent an excellent alternative to satisfy the challenging requirements of many mechanical and aerospace applications. Among these alloys, the heat treatable grades are much appreciated for the possibility to increase the mechanical resistance significantly after solution treatment and aging. The former aims to create a supersaturated solution that is later modified during the latter by the formation of metastable precipitates involving all or some of the alloying elements. In the technical literature, it is well known that the corrosion resistance and the mechanical properties of these alloys, especially the 7xxx grades, strongly depend on the quenching conditions after the solution treatment. This phenomenon is known as “quench sensitivity.” The main aim of this entry is to discuss the influence of the cooling rate during quenching of different commercial aluminum alloys from mechanical and corrosion points of view. The influence of the rolling direction and of the alloy temper will be considered to focusing the attention on some experimental data obtained on the 7075 aluminum alloy.
Nanostructured Aluminum Films: Deep Ultraviolet Absorption from Glancing Angle Physical Vapor Deposition
Authors: Stagon Stephen , Scherzer Ryan
Published: February 2019

This entry reports on the facile fabrication and characterization of aluminum (Al) nanoparticle arrays that absorb strongly in deep ultraviolet. First, Al nanoparticle arrays are fabricated using glancing angle physical vapor deposition and have average diameters of ~30 nm. After subsequent annealing, the structures become oxidized on the exterior with an Al metal core. Ultraviolet visible spectroscopy is performed to characterize the optical absorbance of the structures before and after annealing. The as-fabricated structures show strong and broad absorption centered near ~230 nm, and annealing in air at 400°C results in tightening and blue shifting of the absorption peak. Additionally, annealing results in a decrease in overall absorption intensity. These new results may be potentially useful for tandem or plasmon-assisted photovoltaics.
Grain Refinement and Strengthening of Aluminum Alloys: Cold Severe Plastic Deformation Model
Authors: Guang Qiao Xiao , Gao Nong , Starink Marco
Published: February 2019

This paper presents a model which quantitatively predicts grain refinement and strength/hardness of Al alloys after very high levels of cold deformation through processes including cold rolling, equal channel angular pressing (ECAP), multiple forging (MF), accumulative rolling bonding (ARB) and embossing. The model deals with materials in which plastic deformation is exclusively due to dislocation movement, which is in good approximation the case for aluminium alloys. In the early stages of deformation, the generated dislocations are stored in grains and contribute to overall strength. With increase in strain, excess dislocations form and/or move to new cell walls/grain boundaries and grains are refined. We examine this model using both our own data as well as the data in the literature. It is shown that grain size and strength/hardness are predicted to a good accuracy.
Brazing Aluminum in Low Vacuum
Authors: Perevezentsev B.N. , Sokolova N.M. , Telitsyna G.A.
Published: February 2019

The technology of vacuum brazing components of aluminium and its alloys requires a high vacuum (residual pressure p0 = 10"2–103 Pa) and the introduction of an evaporation getter – magnesium. This requires expensive special equipment with a relatively low productivity even in the presence of multi-chamber continuous furnaces. In addition, it is necessary to clean the chamber and other sections of the vacuum system often to remove the condensate of magnesium and its oxides, with partial dismantling of the furnace. In this article, the authors present the results of investigations into the evaporation of magnesium, the interaction of its vapors with AMts alloy and the special features of formation of brazed joints under low vacuum conditions.
Designing with Aluminum Alloys
Authors: Kim Nack J.
Published: February 2019

This article provides an overview of designing with aluminum alloys. Specific topics included in this review include: alloy designations, heat treatment of aluminum alloys, strengthening mechanisms, properties of aluminum alloys, Al-Li alloys, powder metallurgy of aluminum alloys, cast aluminum alloys, and temper designations. In addition, many reference tables are provided.
Extractive Metallurgy of Aluminum
Authors: Habashi Fathi
Published: February 2019

Aluminum comprises 8% of the earth’s crust and is the most abundant structural metal. Its production has surpassed that of copper and approaches that of iron. This article is a review of all aspects of the production of aluminum including: the raw materials from which it derived, production of aluminum from bauxite, electrolytic reduction of aluminum oxide, purification and refining, and environmental aspects of production processes.
Metal Casting Research: Application to Aluminum Alloy Casting
Authors: Tiryakio Murat , Campbell J.
Published: February 2019

Guidelines for designing research on cast aluminium alloys have been developed to increase the reproducibility of results and make their interpretation more objective. These guidelines, based on the scientific method and recent research findings, are proposed for research on aluminium castings, but they can be easily adapted for other casting alloys.
Shielding Gas: Performance Improvement of MIG and TIG Welding of Aluminum Alloys
Authors: Fortain J.M. , Gadrey S.
Published: February 2019

Welded aluminium alloy products are widely used in the construction and packaging sectors: in this context, in order to be competitive, the welding processes must offer valid solutions from both the productivity and quality viewpoints in addition to health-related aspects with regard to welders and operators. In this context, the technological goals of Air Liquide have been focused on improving the quality of welded joints made using the MIG and TIG processes. The approach adopted here is to examine the various gas mixtures from the viewpoint of influence on electrical parameters (voltage), regularity of filler metal transfer, the surface tension of the melt bath and the convection patterns present in the latter.
Introduction to Aluminum
Authors: Sverdlin Alexey
Published: February 2019

Aluminum is the most heavily consumed non-ferrous metal in the world with an annual consumption of approximately 24 million tons of which it is estimate that 75% of this total amount is primary aluminum (aluminum extracted from ore). This article provides an overview of aluminum ores and their composition, reduction of aluminum, production of commercial quality aluminum, extraction, refinement and the production of ultrapure aluminum.
Microstructure and Properties of Friction Stir Welded Aluminum Alloys
Authors: Kalemba Izabela , Dymek Stanisław
Published: February 2019

Aluminium alloy 7136 belongs to the Al–Zn–Mg–Cu group of aluminium alloys strengthened by precipitation. These alloys offer very good properties, i.e. high strength combined with good corrosion resistance, which makes them suitable for aerospace applications. The limited range of applications of these alloys is due to problems associated with their welding. The Al–Zn–Mg–Cu alloys are classified as non-weldable. The aim of this study was to determine the quality and properties of friction stir welded (FSW) joints of alloy 7136-T76. This article presents the results of a detailed study into the microstructure and mechanical properties of FSW welds. The paper demonstrates that the FSW method is suitable for joining Al–Zn–Mg–Cu alloys. The FSW joints are of good quality and high mechanical properties. Tests of joints created at various tool rotation speeds have shown that joints of suitable quality, in terms of microstructure and properties, can be obtained for a relatively wide range of process parameters. The tool rotation speeds applied during the welding process did not have a significant influence on the quality of the welds.
MIG Welding of Aluminum Alloys
Authors: Yasuda K.
Published: February 2019

MIG welding is used as a highly efficient process for various types of metal. It involves creating an arc between an electrode, wire and the metal to be welded (parent metal) under the gaseous shield of an inert gas such as argon, thereby causing the wire to melt and transfer to the parent metal. This paper mainly describes MIG welding in relation to aluminium alloys.
Properties of Pure Aluminum
Authors: Sverdlin Alexey
Published: February 2019

The properties of aluminum including: light weight, high strength, and resistance to corrosion make it an ideal material for use in applications such as: transportation, food and beverage packaging, construction, defense and aerospace, machinery and tools and consumer products. In addition to reviewing various grades of aluminum, this article will provide an overview of important properties including: crystal structure, density, thermal expansion, thermal and electrical conductivity, Debye temperature, magnetic susceptibility, electrical properties, compressibility, optical properties, solidification and melting, corrosion, mechanical properties and hydrogen solubility.
Plastic Flow of Aluminum in Explosive Welding
Authors: Petushkov V.G. , Zotov M.I. , Dobrushin L.D.
Published: February 2019

Joining of metals in explosive welding takes place as a result of their plastic deformation during a high speed collision and is usually accompanied by typical formation of waves at the interface. In welding aluminium, the weld boundary can also be straight if the speed of the contact point is νc is ≤ 1900 m/s. These welding conditions make it possible to prevent melting of the metal at the interface and increase at the same time its corrosion resistance. In this article, the effect of the dynamic collision angle on the special features of plastic flow of the metal in the vicinity of the contact boundary in welding sheets of AS5 aluminium is described.
Texture–Property Relationships in Aluminum Alloys: Simulations and Experiments
Authors: Raabe Dierk
Published: February 2019

Aluminum alloys provide a huge and increasing application spectrum for formed and cast products. This article texture and anisotropy of aluminum alloys. Topics covered include: experimental determination of surface strains, nanotextures and microtextures, constitutive laws for crystal plasticity finite element simulations and cellular automata for recrystallization, microscopic aspects of texture evolution during plastic deformation and recrystallization, relationship between texture, microstructure and surface properties, integration anisotropy into metal-forming simulations, and crystallographic approximation elastic-plastic anisotropy.
Twist Compression Welding of Aluminum
Authors: Yokota T. , Hashimoto T. , Otsuka M. , Nobutoki M. , Ueki T.
Published: February 2019

Diffusion welding of metallic materials requires contact of clean surfaces by removing surface films. However, there is microscopic unevenness on the surfaces and they are covered with oxide layers, absorbed gas layers, contaminating substance layers, etc. Welding is prevented by this unevenness and by these surface films and it is the stability of the surface films, in particular, which affects welding. Aluminium is regarded as a particularly difficult material for diffusion welding since it has a highly stable strong oxide film. Hence, to weld aluminium, it is necessary to remove this stable film so that welding can be performed. This article describes will describe the result of the investigation into the effect of twist angle, welding pressure and temperature, film thickness and surface roughness on the joint strength of the material.
Wear Behavior of Aluminum Alloys at Slow Sliding Speeds
Authors: Ruiz-Andrés M. , Conde A. , de Damborenea J. , García I.
Published: February 2019

The investigated slow sliding speeds presented in this work enable the understanding of the wear behavior on aluminum alloys and could possibly facilitate the completion of the previously proposed wear mechanism map for aluminum at this slow sliding speed range. Dry sliding block-on-ring wear tests were carried out on aluminum alloys, AA5754 (Al-Mg), AA6082 (Al-Mg-Si), and AA7075 (Al-Zn-Cu), at a very slow sliding speed range (<0.01 m/s). A bearing steel ring of AISI 52100 was used as the counterbody. Tests were performed at varying contact pressures, 20, 100, and 140 MPa, and sliding speeds ranging from 0.001 to 1.5 m/s. The wear tracks and debris collected were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD), with the aim of analyzing their morphology and composition. At relatively slow sliding speeds (>0.01 m/s), the specimens exhibited a wear process placed at the mild wear regime, characterized by oxidation and delamination mechanisms of both the aluminum specimen and the steel ring. However, at very slow speed range (<0.01 m/s), an increase in the wear rate and the friction coefficient is observed for all of the aluminum alloys, thus suggesting that an alternative wear mechanism could be taking place.
X-Ray Diffraction Analysis of the Microstructure of Precipitating Aluminum-Based Alloys
Authors: Mittemeijer E. J.
Published: February 2019

The performance of metallic materials is predominantly determined by their microstructure. The term microstructure is comprised of phase distribution, grain size and shape, lattice defect concentrations and distribution, of the material of interest. In this article an overview is provided of the use of x-ray diffraction (XRD) for microstructural characterization of aluminum alloys. Topics in this review include: the lattice parameter, precipitation kinetics, microstrain, and crystallite size and microstrain from diffraction line broadening,
Rho-of-plant activated root hair formation requires Arabidopsis YIP4a/b gene function
Authors: Gendre Delphine , Baral Anirban , Dang Xie , Esnay Nicolas , Boutté Yohann , Stanislas Thomas , Vain Thomas , Claverol Stéphane , Gustavsson Anna , Lin Deshu , Grebe Markus , Bhalerao Rishikesh P.
Published: February 2019

Root hairs are protrusions from root epidermal cells with crucial roles in plant soil interactions. Although much is known about patterning, polarity and tip growth of root hairs, contributions of membrane trafficking to hair initiation remain poorly understood. Here, we demonstrate that the trans-Golgi network-localized YPT-INTERACTING PROTEIN 4a and YPT-INTERACTING PROTEIN 4b (YIP4a/b) contribute to activation and plasma membrane accumulation of Rho-of-plant (ROP) small GTPases during hair initiation, identifying YIP4a/b as central trafficking components in ROP-dependent root hair formation.
Non-apoptotic function of Drosophila caspase activation in epithelial thorax closure and wound healing
Authors: Fujisawa Yuya , Kosakamoto Hina , Chihara Takahiro , Miura Masayuki
Published: February 2019

Non-apoptotic caspase activation involves multiple cellular events. However, the link between visible non-apoptotic caspase activation and its function in living organisms has not yet been revealed. Here, we visualized sub-lethal activation of apoptotic signaling with the combination of a sensitive indicator for caspase 3 activation and in vivo live-imaging analysis of Drosophila. During thorax closure in pupal development, caspase 3 activation was specifically observed at the leading edge cells, with no signs of apoptosis. Inhibition of caspase activation led to an increase in thorax closing speed, which suggests a role of non-apoptotic caspase activity in cell motility. Importantly, sub-lethal activation of caspase 3 was also observed during wound closure at the fusion sites at which thorax closure had previously taken place. Further genetic analysis revealed that the activation of the initiator caspase Dronc is coupled with the generation of reactive oxygen species. The activation of Dronc also regulates myosin levels and delays wound healing. Our findings suggest a possible function for non-apoptotic caspase activation in the fine-tuning of cell migratory behavior during epithelial closure.
Lmx1a drives Cux2 expression in the cortical hem through activation of a conserved intronic enhancer
Authors: Fregoso Santiago P. , Dwyer Brett E. , Franco Santos J.
Published: February 2019

During neocortical development, neurons are produced by a diverse pool of neural progenitors. A subset of progenitors express the Cux2 gene and are fate restricted to produce certain neuronal subtypes; however, the upstream pathways that specify these progenitor fates remain unknown. To uncover the transcriptional networks that regulate Cux2 expression in the forebrain, we characterized a conserved Cux2 enhancer that recapitulates Cux2 expression specifically in the cortical hem. Using a bioinformatic approach, we identified putative transcription factor (TF)-binding sites for cortical hem-patterning TFs. We found that the homeobox TF Lmx1a can activate the Cux2 enhancer in vitro. Furthermore, we showed that Lmx1a-binding sites were required for enhancer activity in the cortical hem in vivo. Mis-expression of Lmx1a in hippocampal progenitors caused an increase in Cux2 enhancer activity outside the cortical hem. Finally, we compared several human enhancers with cortical hem-restricted activity and found that recurrent Lmx1a-binding sites are a top shared feature. Uncovering the network of TFs involved in regulating Cux2 expression will increase our understanding of the mechanisms pivotal in establishing Cux2 lineage fates in the developing forebrain.
VERNALIZATION1 controls developmental responses of winter wheat under high ambient temperatures
Authors: Dixon Laura E. , Karsai Ildiko , Kiss Tibor , Adamski Nikolai M. , Liu Zhenshan , Ding Yiliang , Allard Vincent , Boden Scott A. , Griffiths Simon
Published: February 2019

Low temperatures are required to regulate the transition from vegetative to reproductive growth via a pathway called vernalization. In wheat, vernalization predominantly involves the cold upregulation of the floral activator VERNALIZATION1 (VRN1). Here, we have used an extreme vernalization response, identified through studying ambient temperature responses, to reveal the complexity of temperature inputs into VRN-A1, with allelic inter-copy variation at a gene expansion of VRN-A1 modulating these effects. We find that the repressors of the reproductive transition, VERNALIZATION2 (VRN2) and ODDSOC2, are re-activated when plants experience high temperatures during and after vernalization. In addition, this re-activation is regulated by photoperiod for VRN2 but was independent of photoperiod for ODDSOC2. We also find this warm temperature interruption affects flowering time and floret number and is stage specific. This research highlights the important balance between floral activators and repressors in coordinating the response of a plant to temperature, and that the absence of warmth is essential for the completion of vernalization. This knowledge can be used to develop agricultural germplasm with more predictable vernalization responses that will be more resilient to variable growth temperatures.