bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Elastic Straining on a 6060 Aluminium Alloy during Natural or Artificial Ageing
Authors: Mørtsell Eva A. , Westermann Ida , Marioara Calin D. , Pedersen Ketill O. , Andersen Sigmund J. , Røyset Jostein , Holmestad Randi
Published: June 2014

The effect on hardness and precipitate microstructure of elastically straining a 6060 Al-Mg-Si alloy during natural ageing or artificial ageing has been investigated. The elastic strain is here defined as 50 % of the material yield strength. All heat treatments where elastic straining was applied led to an increased hardness compared to the unstrained reference material. Quantitative investigations of the precipitate microstructure using transmission electron microscopy (TEM) did not indicate any significant difference in precipitate parameters as compared to the unstrained reference material. Therefore the increased strength in the elastically strained material is being linked to strain induced dislocations based on faster ageing kinetics compared to unstrained reference samples.
Effect of Surface and Grain Boundary on the Reversion of Al-Zn Alloys
Authors: Nakagawa Keiyu , Kanadani Teruto
Published: June 2014

Age-hardening of Al-Zn alloy after quenching develops inhomogeneously due to the effect of surface as a vacancy sink and grain boundary as an easy path. In this study, reversion of the age-hardened Al-Zn alloys, in which ellipsoidal GP zones were formed, was investigated by Vickers micro-hardness test. Ellipsoidal GP zones were reverted more quickly near the surface and grain boundary than in the interior, as spherical GP zones in Al-10%alloy did. It is considered that the surface and grain boundary plays a role of effective source for vacancies, in addition to the interior source such as dislocations, as in the case of the reversion of spherical GP zones.
Role of the Mn-Dispersoids and Mg2Si Particles in the Recrystallization of Automotive 6xxx Alloys
Authors: Ratchev Petar , Jessner Peter
Published: June 2014

Recrystallization control over the whole process route is strictly needed in order to achieve the required texture and properties. An important factor for this is the different type of particles formed in the material, their size and volume fractions. This study addresses the role of the Mn-bearing dispersoids and the Mg-Si (-Cu) particles, forming during different phases of the sheet processing, thus significantly influencing the recrystallization. It will be shown that, when present, the latter ones are playing an important role in the recrystallization control, not only in promoting the recrystallization by means of Particle Stimulated Nucleation, but also retarding it, if the particle size is sufficiently fine. Moreover, they can completely block the recrystallization, if concurrently precipitating during it. The Mn-dispersoids is comparable in its pinning effect, but takes over only when the Mg & Si atoms are in solid solution. Additionally, an update of the Diagram of Humphreys on the effect of particles on the recrystallization of 6xxx alloys is proposed and discussed.
A Study of Cube Grain Nucleation in a Commercial Al Alloy during In Situ and Discontinuous (Ex Situ) Annealing Experiments
Authors: Sukhopar Olga , Gottstein Günter
Published: June 2014

In the current study the nucleation of Cube grains during recrystallization in a commercial Al-Fe-Si alloy was investigated by in-situ and ex-situ annealing experiments at different temperatures. Both methods confirm that the Cube grains can be nucleated during RX both at large deformed Cube bands and other locations. During annealing only about one third of the Cube nuclei from these other locations developed into Cube oriented recrystallized grains owing to an unfavorable growth environment. Such nuclei needed also a longer incubation time due to their small size compared to nuclei formed at large Cube bands which can form nuclei very fast owing to the well-developed substructure and transition zones promoting nucleation. The growth rate of all Cube nuclei was found to be strongly influenced by their environment. This effect became more pronounced with decreasing annealing temperature due to an increasing amount of recovery.
The Effect of Intermediate Annealing Condition on Recrystallization Behavior in Continuous Cast Al-Mn Alloy
Authors: Suzuki Kenta , Sasaki Tomohiro , Anami Toshiya
Published: June 2014

Favorable features such as finer particles and supersaturated solid solution are characterized in continuous casting. In this study, difference of recrystallization behavior was mainly evaluated on two intermediate annealing conditions in continuous cast Al-Mn alloy. One annealing condition was air furnace annealing which corresponds to batch type annealing and is conventionally used to anneal aluminum alloys. Another one was salt bath annealing which simulates CAL type annealing, which is characterized by shorter holding time with rapid heating and cooling. With consideration for application to fin stock in heat exchanger, heat treatment simulating brazing at 600°C was carried out on cold rolled sheets after respective intermediate annealing. After the brazing heat treatment, superior tensile strength and coarser grain structure were attractively obtained with the salt bath intermediate annealed fin. This tensile strength was correlated with much finer particles and more solid solution confirmed after the salt bath intermediate annealing. The coarser grain structure would be brought by changing in recovery and recrystallization behavior during brazing heat treatment.
Recrystallization Behavior of High-Strength AA 7075 Alloy Processed by New Short-Cycled Thermo-Mechanical Processing
Authors: Huo Wang Tu , Guo Ming Xing , Hou Long Gang , Cui Hua , Sun Tao Tao , Zhuang Lin Zhong , Zhang Ji Shan
Published: June 2014

Recrystallization behavior under different conditions (different temperatures and times) of AA 7075 alloy processed by new short-cycled thermo-mechanical processing was investigated to design a suitable recrystallization schedule. With acquiring recrystallization activation energy by DSC, the recrystallization behavior was successfully verified by theoretical calculation. Experimental results of recrystallization response and re-dissolution of precipitates during isothermal annealing reveal excellent agreement with DSC prediction. The results show that the obtained activation energy of recrystallization can be used to establish the relationship between recrystallization temperatures and times. It is proposed that an appropriate recrystallization treatment (703-753 K/1-5 min) could be used to acquire completely recrystallized grains with size <10 μm, contributing to better formability/ductility. The coarsening rate of these fine recrystallized grains is fairly low even though extending the solution treatment times at 753 K. Therefore, it indicates that the recrystallization dynamical equation would be a useful method to adjust recrystallization temperatures and times to satisfy various requirements of structures and properties.
Combined Surface Treatment of Electron Beam Alloying and PVD Hard Coating for Al Alloys
Authors: Buchwalder Anja , Zenker Rolf , Zaulig Erik , Liebich Jürgen , Leuteritz Dietmar
Published: June 2014

Due to their typically high hardness, excellent resistance against wear, and their low coefficient of friction, Physical Vapor Deposition (PVD) hard coatings are used on steels for a wide range of tools and components. Currently, however, the potential for wear protection of Al alloy components cannot be exploited. The thin PVD layers tend to collapse and disintegrate due to plastic deformation of the soft base material. Present research is focused on electron beam (EB) surface alloying, using Co-based additives to increase the surface hardness of the Al base material, producing an improved supporting effect for PVD coatings. The influence of different beam deflection techniques and EB parameters on the microstructure and hardness of alloyed layers was investigated. The properties of the duplex composite layers produced are strongly dependent on the thermal stability of the EB alloyed layers (type and amount of intermetallic compounds, coarsening effects) which are affected by the temperature-time cycle of the PVD process. This will be discussed by means of SEM and EDX investigations in correlation with XRD analysis. Measurements using scratch test with increasing load result in critical load values for the combined treatment that are 3 to 5 times higher when compared to only PVD-coated base material.
Influence of Li Additions on the Microstructure and Corrosion Response of 2XXX Series Aluminium Alloys
Authors: Carrick David M. , Hogg Simon C. , Wilcox Geoffrey D.
Published: June 2014

This paper discusses two Al-Cu alloys for aerospace applications, one of which has an addition of between 1.6 and 2.0 wt.% of Li. The alloys are AA2024-T3 (Al-Cu) and AA2099-T8E77 (Al-Cu-Li). Microstructural analysis via Field Emission Gun Transmission Electron Microscope (FEGTEM) and Field Emission Gun Scanning Electron Microscope (FEGSEM) utilising Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Detector (EBSD) techniques have been used to characterise the two microstructures and phases contained within them. Anodic polarisation and immersion testing in a 3.5 wt.% NaCl solution have been carried out and a comparison of the corrosion mechanisms has been made. AA2024-T3 had a fine, equiaxed grain structure, whereas AA2099-T8E77 had a substantial amount of recrystallized grains. Finer grains were also observed on AA2099-T8E77, however, the vast majority were larger than the maximum detection limit of the EBSD technique. Intergranular and pitting corrosion were observed on both alloys following immersion testing, however, the intergranular corrosion (IGC) was more prominent on AA2099-T8E77. Anodic polarisation indicated that AA2024-T3 was more noble, highlighting that the Li-containing AA2099-T8E77 alloy was more susceptible to corrosion. The T1 (Al2CuLi) phase within AA2099-T8E77 was seen to be highly active following immersion and anodic polarisation tests. The corrosion pits on AA2099-T8E77 were seen to propagate to a depth of ~ 80 to 100 μm, with a maximum of 126 μm recorded. For AA2024-T3 the maximum depth recorded was 77 μm and the average depth was between 60 and 70 μm.
The Effect of Heat Treatment on the Long-Term Corrosion Resistance in Er Containing 5083 Cold Rolled Sheets
Authors: Gao Kun Yuan , Nie Zuo-Ren , Hui Huang , Wen Sheng Ping , Wu Xiao Lan , Ding Yu Sheng
Published: June 2014

The effect of heat treatment on the long-term corrosion resistance of Er containing 5083 aluminum alloy was studied using the micro-hardness test and mass loss test. The microstructure was analyzed by TEM. To maintain the strength, the annealing temperature was selected to be 100-230°C below the recrystallization onset temperature determined by the micro-hardness test. The plot of the annealing temperature versus the Intergranular Corrosion (IGC) initial time, which is determined by the Nitric Acid Mass Loss Test, showed a C-curve. The shortest IGC initial time (~1h) happened at 175°C, the nose temperature of the C-curve. When annealed at 125-200°C, the samples were IGC sensitive with the initial time less than 3h. The entirely IGC resistant (stabilized) samples were obtained when annealed at 220-230°C. The 175°C sensitized treatment was performed on the 220°C-stabilized samples, which showed that the 3-12h stabilization could significantly improve the resistance for long-term corrosion. TEM results showed that, for the IGC sensitive samples, β phases (Al3Mg2) grew along the grain boundary continuously, while for the stabilized samples, they were isolated on triangle grain boundary and phase boundary.
Simulation of Electrodeposition of Al from Ionic Liquid
Authors: Peter Ildiko , Rosso Mario
Published: June 2014

Galvanic deposition of Aluminium on steel substrate, starting from liquid ions, is considered. How the agitation of the liquid during deposition influences the homogeneity of the developed coating layer is investigated by a commercially available FLUENT® ANSYS® solver. Comparison of data coming from numerical simulation with experimentally obtained results are presented. The reported results demonstrate that the deposition process parameter influences the quality of the deposited aluminium.
Effect of Cold Plastic Deformation Prior to Ageing on Creep Resistance of an Al-Cu-Mg-Ag Alloy
Authors: Gazizov Marat , Zuiko Ivan , Kaibyshev Rustam
Published: June 2014

Effect of thermomechanical processing on creep resistance at 150°C of an Al-5.6Cu-0.72Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr (wt. %) alloy was examined. It was shown that increasing strain prior to artificial aging provides achieving high strength. However, a degradation of the creep resistance, i.e., significant decrease in the rupture time and increase in the minimal creep rate, took place, concurrently. The effect of cold rolling on the strength and creep resistance is discussed in relation with the strain effect on the dispersion of secondary phases. The increase in strength and degradation of creep properties of the alloy subjected to cold working before ageing result from superposition of two competitive processes. First, an increase in the lattice dislocation density facilitates the precipitation of Ω-phase plates with high aspect ratio, leading to increase in the static strength at room temperature. Second, acceleration of the diffusion processes results in coarsening of strengthening phase in grain/subgrain interiors and precipitation of Ω-phase on deformation-induced boundaries during creep that deteriorates creep resistance.
Effect of Micro-Voids on Crack Initiation and Propagation in Bending Deformation of Al-Mg-Si Alloy Sheet
Authors: Yamamoto Yusuke , Asano Mineo , Yoshida Hideo , Kobayashi Masakazu , Toda Hiroyuki
Published: June 2014

The crack initiation and propagation during bending have been considered to be affected by second phase particles, micro-voids and shear-bands. However, the effects of the second phase particles and the micro-voids on the crack initiation and propagation during bending have not been fully investigation. In this study, the effect of the second phase particle distribution on the formation of micro-voids, and the effect of the micro-voids on the crack initiation and propagation during bending were investigated using the largest synchrotron radiation facility “SPring-8” and FE-SEM/EBSD. With the bending ratio increasing, the micro-voids increased around the coarse particles near the outer surface. In particular, coarse micro-voids were formed around coarse particles with a high aspect ratio on the shear-bands. At a large cracked part, coarse micro-void was observed at the outmost layer section as a crack initiation site, and coarse micro-voids and asheared fracture surface were observed at the crack propagation site. At the small cracked part with no propagation, cube orientation grains were located under the small crack. It was considered that these cube orientation grains inhibited the formation of shear-bands, therefore, propagation of the cracks did not occur at the small cracked area.
Characteristics of Fatigue Cracks Propagating in Different Directions of FSW Joints Made of 5754-H22 and 6082-T6 Alloys
Authors: Meilinger Ákos , Lukács János
Published: June 2014

The Friction Stir Welding (FSW) is a dynamically developing version of the pressure welding processes. High-quality welded joints can be created using this process for different engineering applications (e. g. automotive parts). Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed to demonstrate the behaviour of the friction stir welded joints under cyclic loading conditions. Fatigue Crack Propagation (FCG) experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints. The CT type specimens were cut parallel and perpendicular to the characteristic directions of the base materials and the welded joints, and the notch locations in the specimens of welded joints were different, too. Therefore, the propagating cracks represent the possible directions of the fatigue cracks both on the base materials and on the welded joints. The results of the fatigue crack propagation tests on the welded joints clearly demonstrate the different characteristics of the thermo-mechanically affected zone (TMAZ), the heat affected zone (HAZ), and the advancing (AS) and retreating sides (RS) of the weld nugget (WN). The investigations and their results were compared with each other and with the results can be found in the literature.
Direct Joining of Aluminum Alloy and Plastic Sheets by Friction Lap Processing
Authors: Okada Toshiya , Uchida Souhei , Nakata Kazuhiro
Published: June 2014

It was difficult to join dissimilar materials such as metallic material and polymer. Conventional joining processes of these materials were mechanical fastening, using adhesion, thermal pressing, laser welding and so on. These processes had disadvantages such as expensive apparatus, restriction of dimension of products and lack of anti-weather resistance.Friction Stir Welding (FSW), which was one of the solid state joinings, was available as a joining process for dissimilar metals. However, in case of joining metal and polymer, it was not available to use the tool for FSW. So we proposed Friction Lap Process to join a metallic material with a polymer and investigated mechanical and metallurgical properties of this dissimilar joint. Itwas described in this paper that joining mechanism is discussed with evaluation of microstructure at the interface between aluminum alloy and polymer. High density polyethylene was not able to be joined for as received aluminum alloy. Anodizing was effective to join with these materials.
Controlling Interfacial Reaction during Dissimilar Metal Welding of Aluminium Alloys
Authors: Wang Li , Wang Yin , Zhang Chao Qun , Xu Lei , Robson Joseph D. , Prangnell Phil B.
Published: June 2014

A critical issue when joining aluminium alloys to dissimilar metals such as magnesium, titanium, and steel is to control the formation of brittle intermetallic compounds (IMCs) that occur due to the reaction at the joint interface. It is demonstrated that once the IMC exceeds a critical thickness, failure of welds always occurs in a brittle manner, with cracks propagating through the IMC. One approach to minimize IMC thickness is to use a solid state joining process, such as friction stir or ultrasonic welding. However, even using these processes, an IMC that exceeds the critical thickness can either form during welding or post-weld heat treatment. In this paper, a number of approaches are discussed to control IMC formation in welds between aluminium alloys and magnesium alloy. Modelling predictions indicate that interfacial reaction rates and grain size of the IMC phases are two critical factors to control layer growth. Experimental results demonstrate that the grain size of IMC layers changes as the layers grow. These modelling predictions and experimental results offer new design strategies to optimize dissimilar metal welding involving aluminium.
Effect of the Zn/Mg Ratio on Microstructure and Mechanical Properties in Al-Zn-Mg Alloys
Authors: Nishi Masatomo , Matsuda Kenji , Miura Naoya , Watanabe Katsumi , Ikeno Susumu , Yoshida Tomoo , Murakami Satoshi
Published: June 2014

It is well know that the 7000 series Al-Zn-Mg alloy has good age hardening ability and high strength among commercial aluminum alloys. In this study, hardness measurement, tensile test, SEM and TEM observation have been performed in order to understand the effect of the Zn/Mg ratio on age hardening behaviour in Al-Zn-Mg alloys. It was seen from hardness measurement that the peak hardness increased with increasing amount of Zn and Mg. Tensile tests were performed for the samples of peak aged condition. It was seen that UTS increased with increasing amount of the Zn and Mg. The elongation decreased with increasing the amount of the Zn and Mg. Intregranular fracture was observed in alloys with low amount of Zn and Mg.Transgranular fracture was observed with high amount of Zn and Mg alloy. TEM observation was performed for peak aged samples. The size of precipitates became finer and the number density increased with increasing Zn and Mg contents.T’ Phase and h1 phase were observed in low Zn/Mg alloy. The h’ phase was observed in high Zn/Mg alloy.
The Effect of Artificial Aging on the Structure and Properties of the Heat-Resistant Alloy V-1213 of Al-Cu-Mg-Ag System
Authors: Oglodkova Yulia S. , Vakhromov Roman O. , Lukina E.A. , Ryabov Dmitriy K.
Published: June 2014

The influence of artificial aging on the phase composition and the properties of sheets made of V-1213 alloy of Al-Cu-Mg-Ag system. It is shown that the phase composition, morphology, dispersion and the density of phase discharge changes with the temperature increase of artificial aging. After the aging at the highest temperature in the range from 150 to 190 °C the maximum density of S' and Ω' phase is observed. This density provides the best combination of mechanical properties when extended at room temperature and high temperature strengthcharacteristics.
Mechanical Behaviour of an AA6082 Aluminium Alloy at Low Temperatures
Authors: Westermann Ida , Hopperstad Odd Sture , Langseth Magnus
Published: June 2014

Aluminium alloys are known to have good cryogenic properties. However, little work is reported on aluminium alloys in the temperature range from room temperature and down to-100°C, which are likely operating temperatures in arctic regions. This work is an experimental study of the low temperature mechanical properties of an extruded AA6082 aluminium alloy in the T6 condition approved for marine applications. Quasi-static and dynamic tensile testing has been carried out at different temperatures from room temperature and down to-70°C. This decrease in temperature leads to a 10 % increase in yield strength. No significant influence of temperature was found on the area reduction to fracture. The work-hardening behaviour has been analysed for different temperatures and strain rates by fitting a generalized Voce rule to the tensile data. The initial work-hardening rate is found to depend weakly on the temperature and strain rate.
Modeling of Bending and Bend-Stretching of Laminated Aluminum Sheets
Authors: Ganesh G. , Jain Mukesh K.
Published: June 2014

Bending and subsequent stretching of sheet materials is typical of many sheet forming operations. Bending and bend-stretching characteristics and limit strain of monolithic AA2024 and laminated tri-layer Alclad 2024 aluminum sheet materials are studied by modeling and experimentation. A computationally efficient analytical model based on advanced bending theory is developed for the laminated sheet materials and utilized to predict the bending characteristics of the above sheet materials. The effects of cladding thickness ratio on the bending characteristics of laminated sheet are compared with the monolithic constituent. Also, predictions from the above analytical bending model are compared with 2D and 3D FE-based bending models. In addition, bend-stretching experiments are conducted using a specialized test jig while continuously recording images using dual-camera set-up from tensile surface and edge of the specimen. A stochastic pattern is applied to the specimen prior to the test and the images are later processed to analyze the development and localization of strains based on digital image correlation (or DIC) method. Strain maps from DIC analysis are utilized to determine the limit strain in the vicinity of the bend line, as well as from FE modeling of bend-stretching tests, using maximum major strain acceleration criterion for localized necking proposed by one of the authors. The results from experimental and modeling work indicate higher limit strains in bend-stretching for Alclad 2024 compared to monolithic AA2024 sheet.
Use of Plane-Strain Tension and Shear Tests to Evaluate Yield Surfaces for AA1050 Aluminium Sheet
Authors: Zhang Kai , Holmedal Bjørn , Hopperstad Odd Sture , Dumoulin Stéphane
Published: June 2014

Plane-strain tension and shear tests were carried out for a fully annealed AA1050 sheet. The tests were simulated numerically with a commercial finite element method (FEM) code using an anisotropic plasticity model including the Yld2004-18p yield function, the associated flow rule and isotropic hardening. The advanced yield function was calibrated by three different methods: using uniaxial tension data combined with FC-Taylor model predictions of the equibiaxial yield stress and r-value, using 201 virtual yield points in stress space, and using a combination of experimental data and virtual yield points (i.e., a hybrid method). The virtual stress points at yielding were provided by the recently proposed Alamel model with the so-called Type III relaxation (Alamel Type III model). FEM simulations of the tests were then made with parameters of Yld2004-18p identified by these three methods. Predicted force-displacement curves were compared to the experimental data, and the accuracy of the parameter identification methods for Yld2004-18p was evaluated based on these comparisons.
Simulation-Based Design of 5xxx Series Alloys with Improved Resistivity against Intergranular Corrosion for Automotive Applications
Authors: Engler Olaf , Brinkman Henk Jan , Hentschel Thomas
Published: June 2014

Resistivity against intergranular corrosion (IGC) is one of the major requirements for AlMgMn 5xxx-series alloys for automotive chassis applications. In 5xxx alloys IGC is caused by the formation of β-Al5Mg3 precipitates along the grain boundaries. Todays 5xxx alloys for chassis applications have been developed such that under specific test conditions they will not exceed a certain mass loss by IGC. However, current developments in the automotive industry will lead to an increased temperature load on chassis parts, in particular for front axle applications in the vicinity of the car engine. Therefore it is to be expected that the properties of the existing 5xxx series alloys will not be sufficient any more.
Certain alloy elements, including Mn, Cr, Cu and Zn, alter type and morphology of the Mg-bearing precipitates and, hence, reduce the sensitivity against IGC. The present study was aimed at developing a series of Zn-containing Al alloys which are free of IGC, while maintaining mechanical properties of current 5xxx chassis alloys. Alloy development was performed by micro-chemistry simulation with the aim to avoid the formation of the detrimental β-Al5Mg3 precipitates. Eventually a series of three alloys was cast and processed on lab scale and tested for mechanical properties and resistivity against IGC after application of various critical time/temperature scenarios in order to validate that the newly developed alloys are free of IGC.
Thermodynamic Assessment and Determination of Spinodal Lines for Al-Zn Binary System
Authors: Kogo Shosuke , Shoichi Hirosawa
Published: June 2014

Calphad type thermodynamic assessment of Al-Zn binary system was performed to calculate the metastable phase diagram including not only miscibility gap but also spinodal lines. The Gibbs free energy for liquid, fcc and hcp phases was evaluated by taking into account available experimental data, and most of them were satisfactorily reproduced by our thermodynamic descriptions. Furthermore, the Gibbs free energy for GP zones was also expressed by combining the chemical energy for solid solution of fcc-Al with appropriate elastic strain energy, in good agreement with experimentally reported solubility limits. Therefore, the spinodal lines derived from the differential of the Gibbs free energy could be also reasonably estimated, although those are quite difficult to be measured experimentally.
Numerical Damage Modelling of Aluminium Alloys for Wide Range of Stress Triaxiality
Authors: Horr Amir M. , Kertz Richard , Just Michael
Published: June 2014

There have been many efforts to investigate and develop a mechanical plasticity, damage and failure models for metal alloys in the last couple of decades. These models (single and multi-damage parameters) are generally based on energy and constitutive equations to simulate the fracture and failure processes in metal alloys. The conventional fracture mechanics theory and its applications have been successfully employed to study fracture and failure processes. However, these methods have serious short comes in predicting the damage and failure in metal alloys where the fracture is dominated by the presence of defects like micro-voids (and their growth, nucleation and coalescence), oxides and inclusions. In the present study, following the in-depth study of damage initiation and progression in aluminium alloys, a frame work has been setup to develop a numerical model for damage accumulation. Based on the existing phenomenological damage theory, a mathematical basis for damage initiation and also damage accumulation under wide range of stress triaxiality (including near pure shear) has been developed. The damage model has been checked and verified using a result of experimental-simulation comparative study. The experiments have been carried out using samples made from squeezed and high pressure casting step plates. One of the main contributions of this paper is to show the advantages of using plasticity-based modified damage models to investigate the damage accumulation in cast aluminium alloys.
Thermal Stability of Al-Cu-Mg Alloys
Authors: Pouget Gaelle , Sigli Christophe
Published: June 2014

The Al-Cu-Mg alloys currently used at elevated temperature for aerospace applications, such as 2618 and 2219, were developed in the 1950s. Since then, not only have property requirements evolved significantly with the widespread introduction of damage tolerant design, but also the understanding and modelling capacity of the alloys' property-composition-processing relationships have developed beyond recognition. Moreover there is a renewed need for higher strength/toughness, higher temperature solutions in many aircraft's hot areas.A kinetic model has been developed to predict the strengthening capability and the thermal stability of hardening phases. It is based on a homogeneous nucleation, growth and coarsening model applied to S' (Al2CuMg) and θ' (Al2Cu); the yield strength is then calculated from the precipitates' size distribution. It suggests two areas of interest in the Al-Cu-Mg diagram.Three targeted compositions were then explored inside and outside the areas of interest and their thermal stability assessed up to 250°C. Different behaviours were observed and are explained by the strengthening potential and the coarsening resistance of S' and θ'. The two interesting areas for thermally stability are confirmed. An area of poorer thermal stability was also identified, associated with a high Cu content in solid solution which accelerates precipitate coarsening kinetics.
Study of Aging Precipitation of Al-Zn-Mg Alloys with Er Additions by Monte Carlo Simulation
Authors: Rong Li , Lin Liu Qiu , Wu Xiao Lan , Li B.L. , Wen S.P. , Huang H. , Nie Zuo-Ren
Published: June 2014

Our former experimental study showed that the addition of Er to Al-Zn-Mg alloys speeded up the aging precipitation, accelerated the precipitation of and enhanced the effect of aging strengthening distinctively. In this paper, the Monte Carlo method was applied to simulate the microstructural evolution of Al-2.6Zn-(2.3Mg)-(0.07Er), Al-2.6Zn-2.3Mg-(0.12Er), and Al-2.6Zn-2.3Mg-0.1(Er,Zr) alloys during aging. The effects of Er addition to Al-Zn-Mg alloys on the clustering of Zn and Mg atoms are studied through analysis of the simulation results and the effects on the subsequent aging process are discussed as well. The results show that the Zn/Mg/Er clusters appear beside the Zn clusters, Mg clusters and Zn/Mg clusters in the Er addition Al-Zn-Mg alloys. The Zn clusters and Zn/Mg clusters are finer in the Al-2.6Zn-2.3Mg-xEr alloys than that in the Al-2.6Zn-2.3Mg alloys without Er addition. The size of the Zn clusters and Zn/Mg clusters in the Al-2.6Zn-2.3Mg-0.07Er is eight percent and nineteen percent smaller than that in the Al-2.6Zn-2.3Mg alloys without Er addition respectively. This precipitation refinement effect of Er addition to the Al-2.6Zn-2.3Mg alloys is enhanced with the increment of Er content. These above results are consistent with the experimental results that the precipitation in the Al-Zn-Mg alloys with Er is finer and denser than that in the Al-Zn-Mg alloys without Er. The Er addition changes the clusters distribution in the Al-Zn-Mg alloys by its interaction with the main solute atoms and the vacancy, and thus influences the precipitations during subsequent aging processing.
Constitutive Analyses of Tensile Tests on Pre-Rolled AA3003 Sheets
Authors: Saimoto Shigeo , Inal Kaan , Jin Hai Ou
Published: June 2014

A new rationale to assess the work-hardening locus for pre-rolled sheets is described based on the realization that since the internal stresses necessarily sum to zero, the mean dislocation density remains the same upon re-pull in the rolling direction. Thus the 0.2 % yield stress as function of thickness strains results in an estimate of the stress-strain relation during rolling. Under plane strain, the thickness strain is negative to that of extension and hence the deduced rolling locus is compared to that of extrapolated tensile one of the start sheet. This comparison indicates that the onset of Stage IV occurs when volume fraction of point defects produced attains about 2 %.
An Advanced Dynamic Repair of Edge Crack Aluminum Plate with a Composite Patch
Authors: Lecheb Samir , Nour Abdelkader , Chellil Ahmed , Mechakra Hamza , Amarache Ali , Kebir Hocine
Published: June 2014

In this work, repaired crack in 2024 T3 aluminium plate with composite patch is presented, the problem is handled in plane stress condition under tensile Mode I crack growth. In the numerical simulation, firstly we determine the displacement, strain and stress, also the first six mode shapes of the plate, secondly we compare the first results with result of a cracked plate, thirdly we repair the crack with composite patch for different materials ( Glass, Boron, carbon) and for ( 2 layers, 4 layers). Finally the comparison of stress, strain, displacement and six first natural frequencies between uncracked, crack initiation and composite patch repair crack. The best offer operating according to the need is selected.
Modeling of Static and Geometric Dynamic Recrystallization during Hot Extrusion of Al-Mg-Si Alloy
Authors: Sherstnev Pavel , Zamani Adrian
Published: June 2014

Under certain conditions of extrusion temperature and strain rate Al-Mg-Si alloys produce coarse recrystallized grains at and near the surface. Current FEM models are able to analyze grain size evolution for extruded profiles, but cannot predict the coarse recrystallized grains near the surface. A new model using DEFORM 2D and local state variables such as strain, strain rate and temperature is compared with Al-Mg-Si rods extruded at 440°C and 500°C for two extremes of strain rate. The model is found to be sensitive to the processing conditions and to accurately predict the recrystallized grain size and fraction.
Visualization of Micro-Segregations in A356 Aluminum Alloy by a Color Etching Method
Authors: Gao Li , Harada Yohei , Kumai Shinji
Published: June 2014

An A356 aluminum alloy billet which has a dendritic microstructure was compressed and then partially re-melted to semi-solid state before water quenching, by which the spheroidization of Al grains was realized. A color etchant called Weck's reagent was used to characterize both the dendritic and spheroidal microstructure. In both cases, distinct color differences were observed inside Al grains by normal optical microscopy. Interestingly, a dendritic-shaped structure inside the spheroidal Al grains was visualized, which should be the reflection of the original dendrite before heating and partial re-melting. Also, the grain growth during water quenching could be clearly visualized after etching with this reagent. As a result, solid fractions could be evaluated more precisely by excluding the grain growth when measuring the area of solid phase in 2-D micrographs. In order to investigate the coloring mechanism, electron probe micro-analyses were carried out to characterize the micro-segregations inside an Al grain. Results showed that the micro-segregation of Ti had a strong correlation with the color difference. Detailed investigation found that the micro-segregation of Ti could be preserved after heating and partial re-melting due to the extremely low diffusion rate of Ti in Al.
Quantitative Phase Analysis of Al-Mg-Li and Al-Cu-Li Alloys
Authors: Betsofen Sergey , Chizhikov Mihail
Published: June 2014

On the basis of the balance equations of chemical and phase composition of the Al-Mg-Li and Al-Cu-Li alloys developed a method of determining the amount of intermetallic phases from the experimentally measured value of the lattice parameter of α-solid solution. In alloys of Al-Mg (Cu)-Li the relative phase ratio of the δ'(Al3Li) and S1 (T1) are determined by the atomic percentage ratio of the Li and Mg (Cu).
In Situ Isothermal Calorimetric Measurement of Precipitation Behaviour in Al-Mg-Si Alloys
Authors: Giersberg Lydia , Milkereit Benjamin , Schick Christoph , Kessler Olaf
Published: June 2014

Isothermal time-temperature-precipitation (TTP) diagrams deliver important material data like temperature and time ranges critical for precipitation. During the last years an in-situ calorimetric method to record continuous cooling precipitation diagrams has been developed to application level by our group. However, isothermal TTP-diagrams were still determined by ex-situ analyses only. In this work in-situ measurements of precipitation reactions were carried out during isothermal soaking. Therefore the whole heat treatment cycle was performed in a differential scanning calorimeter (DSC). Al-Mg-Si-alloys 6063 and 6005A were analysed. Solution annealing and overcritical quenching to several temperatures between 450 °C and 250 °C was followed by isothermal soaking. Based on the heat flow curves during isothermal soaking TTP-diagrams were determined. Further microstructure investigations by scanning electron microscopy and hardness tests after artificial ageing were performed. Both alloys show similar results. In the TTP-diagramms three so-called ”C-curves” could be observed. Every C-curve is expected to represent precipitation of a different phase. Hardness and microstructure investigations correspond with the data of the TTP-diagramms.
Investigation of Grain Boundaries in an Al-Mg-Si-Cu Alloy
Authors: Holmestad Jon , Ervik Martin , Marioara Calin D. , Walmsley John Charles
Published: June 2014

The grain boundaries of a fibrous Al-Mg-Si-Cu alloy have been investigated with Transmission Electron Microscopy. The compositions have been mapped by Energy Dispersive X-ray Spectroscopy. The alloy has been aged for 12 hours at 155°C after solution heat treatment and is in a slightly underaged condition. The precipitates nucleated on the high angle grain boundaries are coarse, while the precipitates on the low angle grain boundaries are smaller and more numerous. The precipitates on both types of grain boundaries has been identified as Q'-type. Copper is segregated to both the low and high angle grain boundaries. The effect of this segregation will be discussed with regards to the corrosion properties of the alloy.
Formation Behavior of Nanoclusters in Al-Mg-Si Alloys with Different Mg and Si Composition
Authors: Kim Seong Nyeong , Kobayashi Equo , Sato Tatsuo
Published: June 2014

Two types of nanoclusters are formed during low temperature aging and play important roles in age-hardening of Al-Mg-Si alloys. The formation behavior of these nanoclusters depends on the alloy composition and heat-treatment process. In this work, the various alloys with different Mg and Si concentration were used in order to clarify the influence of alloy composition on the nanocluster formation using differential scanning calorimetry (DSC), hardness and electrical resistivity measurements. Based on the DSC results, two overlapped exothermic peaks were clearly detected, showing the formation of Cluster (1) and Cluster (2) in all examined alloys with different alloy composition. These two overlapped peaks are separated by the Gaussian function method to analyze the volume fraction of nanoclusters quantitatively. It is found that the Si and Mg concentration of Al-Mg-Si alloys has a marked effect on the nanocluster formation. The formation of Cluster (1) is more related with the Si concentration, whereas Cluster (2) is correlated with both of the Mg and Si concentration. Furthermore, the important point is that the formation behavior of nanoclusters strongly depends on the Mg/Si ratio of the alloys. The formation of nanoclusters is most enhanced when the Mg/Si ratio is approximately 1.0.
TEM Observation of Precipitate Structures in Al-Zn-Mg Alloys with Additions of Cu/Ag
Authors: Watanabe Katsumi , Matsuda Kenji , Ikeno Susumu , Yoshida Tomoo , Murakami Satoshi
Published: June 2014

Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg alloy, were prepared to compare the effect of the additional elements on the aging behavior. The content of Ag and Cu were 0.2at.% and the same as, respectively. Ag or Cu added alloy showed higher maximum hardness than base alloy. The particle shape and rod shape precipitates were observed in all alloys peak-aged at 423K. According to addition of Ag or Cu, the number density of the precipitates increased higher than that of base alloy.
TEM Observation for Precipitates Structure of Al-1.0Mass%Mg2Ge Alloys Aged at 473K
Authors: Kawai Akihiro , Matsuura Keisuke , Watanabe Katsumi , Matsuda Kenji , Ikeno Susumu
Published: June 2014

It is known that Al-Mg-Ge alloys show a similar precipitation sequence to that of Al-Mg-Si alloys, and that ther equilibrium phase is β-Mg2Ge according to the phase diagram. In this study, the precipitation sequence and age-hardening behavior of Al-1.0mass%Mg2Ge alloys has been investigated by hardness test, write out in full first time used TEM and HRTEM observations on.The hardness curves showed no big difference between peak values hardness for samples aged at 423, 473 and 523K. The precipitates in the peak-aged samples have been classified as some metastable phases, such as the β’-phase and parallelogram-type precipitates by HRTEM observation. The large precipitates are similar to the A-type precipitate in the Al-Mg-Si alloy with excess Si.
Nanocluster Formation and Two-Step Aging Behavior of Rapid Hardening Al-Mg-Cu(-Ag) Alloys
Authors: Mihara Mami , Kobayashi Equo , Sato Tatsuo
Published: June 2014

The characteristic age-hardening response of Al-3.0Mg-1.0Cu (mass%) alloys with and without Ag addition has been investigated by the hardness measurement, differential scanning calorimetry (DSC) and electrical resistivity measurement. The alloy compositions locating in the (α+S+T) phase field of the Al-Mg-Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g. within 60 s at 443 K) and contributes to increase hardness as much as 50 % of the total age-hardening. In the Ag-added alloy, the hardness change during the first stage of hardening is larger and the plateau stage is shortened as a result of the fast arrival at the second stage of hardness. Small amount of Ag changes the age hardening response of the Base alloy dramatically. In the low temperature aging, the incubation stage at which no clear hardness and electrical resistivity increase appears for a long period before the first stage of hardening. After the pre-aging at this incubation period, a characteristic two-step aging response is observed. The peak hardness dramatically changes in the Al-3.0Mg-1.0Cu alloy, while no clear change in the Ag-added alloy.
Connections between masserie and historical roads system in Apulia
Authors: Caliandro Lucia P. , Loisi Rosa V. , Dal Sasso Pasquale
Published: June 2014

A precise category of Apulian farmsteads, known as masserie, is a significant example of rural buildings featuring relevant architectural and landscape characteristics. Their territorial distribution is diversified and often depend on the close relationship between the building and its adjacent agricultural lot. Moreover, owing to their specific role in overseeing the territory and asserting land tenure rights, Apulian masserie distribution may have genetic origins influenced by other elements, too. The aim of this work is to investigate the existing relationships between masserie and historic roads crossing the Apulia region (Roman roads and sheep’s paths called tratturi), considering both their mutual distance and the individual rural buildings importance. Overlay mapping procedures allow to quantify the amount of masserie falling within the catchment areas of the aforementioned historical roads, while historical and territorial in-depth analysis helped to identify those elements characterising the most interesting masserie from cultural and architectural points of view. The research provided interesting qualitative and quantitative information on the existing relations between these assets, leading to further considerations on the possibility to enhance them through the promotion of their integrated recovery.
In memory of Professor Adriano Guarnieri
Authors: Editors The
Published: June 2014

On the 27th March 2014 Professor Adriano Guarnieri Editor-in-Chief of this Journal has died. In 1998 he became Editor-in-Chief of the Journal of Agricultural Engineering formerly known as Rivista di Ingegneria Agraria. From the beginning he worked to the improvement and development of the Journal, contributing to its turning from a national printed journal into a full access international journal. His work has paid off also after his death, with the notable achievement of the journal being accepted for inclusion in Scopus Bibliographic Database.
Grateful for his work, to pay tribute to the researcher, a short resume of his career is reported.
Yugoslav Eulogies: The Footprints of Gavrilo Princip
Authors: Miller Paul
Published: June 2014

While scholars have intensively studied Yugoslavia’s weaknesses and dissolution (both in the interwar and post-World War II eras) from political and economic perspectives, there has been less work on the issue of cultural cohesion so crucial to Yugoslavism (the Yugoslav idea) as it was conceived and developed in the nineteenth century and elaborated upon during World War I.  In particular, there has been little attempt to interrogate the long-term (1918–today) discursive construction of Yugoslav identity by means of collective memory—that is, the selectively shared stories people tell about themselves in order to give meaning to the ‘nation,’ a sense of belonging to the ‘national culture.’  And yet from the moment Yugoslavia was created, ordinary Yugoslavists began constructing the Sarajevo assassination as a heroic narrative of opposition and liberation that transcended the particularist identities of ethnicity, nation, religion, and history.  How did the different Yugoslav regimes and post-Yugoslav political elites respond to these efforts to shape a collective cultural memory around Gavrilo Princip’s political murder of the Archduke Franz Ferdinand, heir to the throne of the Austro-Hungarian Empire?  What can the various manifestations of this memory and official attitudes towards it tell us about the Yugoslav national project writ large?  These are the main themes addressed in my paper.