bluuebunny/crossref_metadata_2025 huggingface dataset:
Lifecycle Assessment and Lifecycle Costing of Aluminium Wrought-to-Wrought Recycling
Authors: Hammervold Johanne , Pettersen Johan , Moe Bjørnbet Marit
Published: June 2014

The aluminium scrap market is undergoing rapid changes which will trigger off new recycling strategies. As the cast scrap market saturates it will become economically feasible to apply scrap also in aluminium wrought alloy production. As part of an EU project, Sustainable and efficient Production of Light weight solutions (SuPLight) a method for assessing life cycle environmental and economic consequences of applying aluminium scrap in high-end products has been developed. In this work, the method has been applied to assess life cycle environmental and economic impacts for six scenarios, embracing five various strategies for scrap treatment. This includes processes in material and component production, as well as fuel use during operation of vehicle and end-of-life treatment. The model for scrap strategies includes three grades of sorting and separation, plus simple refining by low-temp electrolysis and fluxing, and refining by Hoopes process. Not surprising, we find that sorting is beneficial compared to refining. More notable, perhaps, is the relative large difference between scenarios with regards to the environmental impacts considered. Finally, we discuss benefits from the life-cycle evaluation of scrap scenarios and use of the tool in business development.
Effect of Potential on Hydrogen Evolution during Pitting of Aluminum
Authors: Haruna Takumi , Nishiwaki Daiki , Nishikawa Midori
Published: June 2014

Effect of potential on hydrogen evolution during simulated pitting of aluminum has been investigated. Aluminum wire in 1.0 mm diameter was mounted in resin, immersed in 0.6 kmol.m-3 NaCl solution and anodically dissolved in axial direction by applying a constant potential from-0.6 to-0.1 VAg/AgCl for 86.4 ks. In addition, a resistance of the solution in the crevice of the resin where the aluminum wire corroded was simultaneously measured by superimposing high-frequency alternating potential (Ep-p=10 mV) to the main potential. As higher main potential was applied, the corrosion depth increased. Hydrogen evolved at the corroded site although the anodic potentials were applied. The amount of hydrogen evolution increased as higher main potential was applied to the wire. An interfacial potential (Eint) at just the wire surface was calculated from applied main potential (Eapp), solution resistance (Rsol) and current (I) as Eint = Eapp - I.Rsol. The interfacial potential was about-0.7 to-1.0 VAg/AgCl, and became lower as the higher main potential was applied. The lower interfacial potential may cause hydrogen evolution in this case.
Microstructure and Mechanical Properties of Ductile Aluminium Alloy Manufactured by Recycled Materials
Authors: Yang Hai Lin , Ji Shouxun , Watson Douglas , White Mark , Fan Zhong Yun
Published: June 2014

The present paper introduces the microstructure and mechanical properties of the Al-Mg-Si-Mn alloy made by recycled materials, in which the impurity levels of iron are mainly concerned. It is found that the increased Fe content reduces the ductility and yield strength but slightly increases the UTS of the diecast alloy. The tolerable Fe content is 0.45wt.%, at which the recycled alloys are still able to produce castings with the mechanical properties of yield strength over 140MPa, UTS over 280MPa and elongation over 15%.The Fe content is steadily accumulated in the alloy with the increase of recycle times. However, after 13 cycles, the recycled alloys are still able to produce ductile alloys with satisfied mechanical properties.
Model Experiment on Removal of Nonmetallic Inclusions by Bubble Flotation
Authors: Shimasaki Shin Ichi , Narita Shunsuke , Taniguchi Shoji
Published: June 2014

A new experimental technique, which is based on a kinetic model of particle transport, has been proposed for determination of the capture efficiency of particles by bubble flotation. Cold model experiments by using an aqueous solution and plastic particles are carried out to validate the new experimental technique. Plastic particles having poor wettability tend to adhere to bubbles and they are removed from an aqueous solution by bubble flotation. On the other hand, plastic particles good in wettability are not captured by bubbles. Capture efficiency can be estimated from a difference of transfer rate between the particles having poor and good wettability. The capture efficiency is found to be proportional to the size ratio of particle and bubble, dp/db, and agrees with theoretical results of Sutherland (1948) for a potential flow condition.
Effects of Cu or Li Addition and Multi-Step Aging Conditions on the Bake-Hardenability of an Al-Mg-Si Alloy
Authors: Koshino Yuki , Shoichi Hirosawa , Aruga Yasuhiro , Shishido Hisao , Matsumoto Katsushi
Published: June 2014

In recent years, automobiles with lower fuel consumption are required because the exhaust fume is severely regulated. The weight-saving is quite effective to realize such low fuel consumption, and therefore aluminum alloy becomes attractive as an alternative material of steels due to its high specific strength. 6XXX series Al-Mg-Si alloys exhibit good bake-hardenability during paint-bake treatment in the automobile manufacturing process, but to reduce further environmental impact, the paint-baking temperature is supposed to be lowered than the present temperature of about 443K. In this study, it was aimed to investigate the attained hardness after paint-bake treatment at various temperatures of 408-443K for an Al-0.55wt%Mg-0.90wt%Si alloy with/without microalloying elements of Cu and Li. The effects of multi-step aging conditions; e.g. pre-aging, natural aging and paint-bake treatments, were also investigated through Vickers hardness test, TEM observation and DSC analysis. From the obtained experimental results, it was clarified that the addition of Cu or Li to the Al-Mg-Si alloy increases the attained hardness even at a paint-baking temperature of 408K due to the increased volume fraction of precipitates. Furthermore, pre-aging treatment at 373K for 18ks was also effective in suppressing the increase in hardness during natural aging, resulting in the highest attained hardness among the investigated multi-step aging conditions; i.e. HV100 in the Li-added alloy paint-baked at 408K.
Full through Process Simulation for Low Pressure Die Casting – From Casting to Design
Authors: Horr Amir M. , Angermeier Christoph , Harrison Angela
Published: June 2014

To achieve a required product quality during Low Pressure Die Casting (LPDC) process, it is necessary to identify and also control the main input parameters affecting the casting defects to arrive at the desired output quality. In industrial scale LPDC, where the issues of part quality, cost, and cast speed are the main driving forces for the industries, the cast process optimization to have minimum defects is quite essential. The LPDC process of light weight metals is defined as a casting process where the die is filled relatively slowly at low pressure. The melt flow regime has low turbulence, and filling process can be defined as relatively smooth filling. In recent years, in order to limit the component defects, the through process simulation has widely been used. In an interactive simulation environment, a full multi-phase casting process simulation (thermal-fluid simulation using multi-physical domain) along with its material and mechanical simulations are carried out in a single environment. One of the main contributions of this paper is to show the advantages of using full through process simulation of LPDC to limit the defect in the component. An experimental program along with a comprehensive process simulation has been setup to optimize the casting process and the results were presented for real world case studies.
Characterisation of Al-Cu and Al-Mg-Si Free-Cutting Alloys
Authors: Karlík Miroslav , Faltus Jiri , Nejezchlebová Jitka , Haušild Petr , Harcuba Petr
Published: June 2014

Free cutting alloys of Al-Cu (AA2011 and AA2111B) in T6 temper and Al-Mg-Si system (AA6023 and AA6262) in tempers T6 and T8 were subjected to Charpy U - notch impact testing at the temperatures ranging from 20°C to 350°C. The microstructure of the materials was characterized by light metallography, fracture surfaces were observed using scanning electron microscope (SEM). The alloys showed a significant decrease in the impact energy KU at temperatures ~125°C (AA2011, AA2111B), ~170°C (AA6023), and ~250°C (AA6262), respectively. This decrease of KU was caused by melting of disperse phases containing low-melting point metals (Pb, Sn, Bi), which was confirmed by differential scanning calorimetry. Additional annealing of the AA6262-T8 alloy for 2h at 400°C followed by slow cooling led to the transformation of Pb + Bi particles accompanied by the shift of the melting temperature from ~250 to ~310 °C. Higher temperature solution annealing of the AA6023 alloy for 30 min at 540°C (as a replacement of common 30 min at 520°C) resulted in a partial transformation of Sn + Bi particles accompanied by melting point shift from ~170 to ~200°C. Chemical composition of the corresponding phases was monitored by energy dispersive X-ray spectroscopy in SEM.
Effects of Deformation Heating on Constitutive Analysis of a New Al-Mg-Si-Cu Alloy during Hot Compression
Authors: Yang Dong , Quan Yong Hong , Zhao Huan , Zhang Zhi Qing , Huang Guang Jie , Liu Qing
Published: June 2014

A new Al-Mg-Si-Cu aluminum alloy was hot compressed at temperatures between 320°Cand 530°Cand strain rates between 0.001 s1 and 10 s1 using a Gleeble-1500 thermo-simulation machine. The effects of deformation heating on flow stress were analyzed and corrected, and a comparison was made of hyperbolic-sine constitutive equations with and without correction. The results show that the deformation heating apparently increases the flow stress at strain rates of 1 s1, 10 s1. The thermal activation energy values were 325.12 KJ/mol and 304.47 KJ/mol before and after correction, respectively.
Modification of Eutectic Si in Al-Si Based Alloys
Authors: Li Jie Hua , Albu Mihaela , Ludwig Thomas , Matsubara Y. , Hofer Ferdinand , Arnberg Lars , Tsunekawa Y. , Schumacher Peter
Published: June 2014

The paper provides a new insight into the modification of eutectic Si in Al-Si based alloys. To date, impurity-induced twinning mechanism and twin plane re-entrant edge mechanism are the well-accepted theories. However, neither IIT nor TPRE can be used to interpret all modification observations. Therefore, a re-consideration of modification mechanisms is still required. In this contribution, recent advances on the understanding the modification of eutectic Si are reviewed. Two different cases are highlighted. In the case of Sr, Na and Eu addition, eutectic Si was modified from a faceted to a fibrous morphology, which involves the formation of multiple Si twinning. In the case of Yb and Ca addition, eutectic Si was refined to a smaller size, but still maintained a plate-like morphology. The possible modification mechanism was thus discussed in terms of (i) adsorption of atoms at twin re-entrant edge, and (ii) segregation across {111}Si growth planes. Furthermore, solute entrainment of modifying elements (M) was introduced to interpret the formation of Al2Si2M phase or M-rich clusters within Si crystals.
A New Approach of Casting Aluminium Alloy Bar by Applying Low Frequency Electromagnetic Field
Authors: Wang Xiang Jie , Sun Gang , Wang Li Juan , Li Peng Wei , Cui Jian Zhong
Published: June 2014

Aluminum is the richest metallic element in the earth, the ingots cast by DC casting process are usually extruded into aluminum bars. When the final products do not require high strength, this process appears to be low efficiency and high cost. We try to design a new technology to cast aluminum bar by horizontal direct chill (HDC) casting process directly. An electromagnetic field is applied during the horizontal continuous casting of 6061 aluminium bar with a diameter of 30mm. The experimental results show the asymmetry of the sump can be overcome by electromagnetic field. Ingot with good upper and lower surface quality is obtained. The structure of ingot is refined and the angle between growth direction and horizontal direction becomes small with increasing casting speed.
Detection of Phase Transition in Free-Cutting Al-Mg-Si Alloys by Resonant Ultrasound Spectroscopy
Authors: Nejezchlebová Jitka , Seiner Hanuš S. , Karlík Miroslav
Published: June 2014

The transition temperatures of small amounts of eutectic particles contained in free-cutting aluminum alloys (namely AA6262 and AA6023) are investigated in this paper. Detection of the transition temperatures by conventional differential scanning calorimetry (DSC) measurements is difficult because of the small volume fraction (~ 1wt.%) of the eutectic. On the other hand, the melting of the particles induces small changes of elastic moduli of the alloy, which can be sensitively measured by resonant acoustic methods, for example by resonant ultrasound spectroscopy (RUS). It is shown that the phase transitions of the particles correspond to well-detectable changes of the resonant spectrum, which enables a more detailed characterization of the transition process. A significant thermal hysteresis is observed between the cooling and the heating runs, and also the widths of the temperature ranges in which the transitions occur exhibit a strong melting/freezing asymmetry.
Effect of Alloying Elements on the Colour Development of Anodised Al-Mg-Si Alloys
Authors: Senel Esma , Hallenstvet Merete
Published: June 2014

Colour of the anodised Al-Mg-Si alloys was quantified by spectrophotometric method defining L* (lightness), a* (greenness-redness) and b* (blueness- yellowness) values. All alloys exhibited yellow and green colour. The yellowness of the anodised surfaces increased significantly with the increase of Cu while increasing Mn reduced the greenness. Effect of trace elements V and Ni was negligible while Zn caused slightly yellowness. Fe reduced the lightness of the surfaces, while its effect on colour was insignificant. Smut layer being formed during alkaline etching (prior to anodising) was desmutted/deoxidised in different acid solutions, some of which failed to clean the etched surfaces. Remaining smut however caused minor effect on colour.
Prediction of Fatigue Life for Light Metals and their Welded Metals
Authors: Enomoto Masatoshi
Published: June 2014

A6N01 (6005C in ISO) base metal is applied for cantilever type fatigue test over 108 cyclic number. Fatigue strength decreases over 107
and after testing, new prediction formula of fatigue life at high cycle regeion which named YENs formula is proposed for light metal and their welded joints. This formula is shown as below.
Log (σa/σp) =k Log (Nf-N0)+m
σa is stress amplitude, σp is proof stress k is depend on stress concentration factor
Nf is fatigue life without residual stress and No is discrepancy due to residual stress.
m is material constant. This formula is a hypothesis and it is required to accumulate much more fatigue data for many kind of alloys and their welded joints.
Effect of Electroless Ni-P Plating on the Fatigue Strength of Dilute Al-Si Alloys
Authors: Nagata Norihito , Kanadani Teruto , Fukuhara Minoru , Hino Makoto , Murakami Koji
Published: June 2014

In this study, the effect of electroless Ni-P plating on the fatigue strength of dilute Al-Si alloys was investigated. As results, the following points were clarified. Fatigue strength of the specimen subjected to zincate treatment only after furnace cooling treatment was almost the same as the furnace cooling only. Fatigue strength of the specimen subjected to Ni-P plating after furnace cooling treatment, was reduced overall, except for high-stress region, rather than one of non-processing materials. Fatigue strength of the specimen subjected to Ni-P plating after aging treatment showed a clear increase in comparison with one of non-processing materials. Breaking elongation of the specimen subjected to Ni-P plating after aging treatment showed no significant changes in comparison with one of non-processing materials. On the other hand, breaking elongation of the specimen subjected to Ni-P plating after furnace cooling treatment reduced by half in comparison with one of non-processing materials. Especially, it seems that poor fatigue strength and ductility of plating materials are mainly caused due to interaction between surface precipitates and hydrogen gas.
Influence of Particles on Short Fatigue Crack Initiation in 2050-T8 and 7050-T74
Authors: Nizery Erembert , Buffière Jean Yves , Proudhon Henry , Daniélou Armelle , Forest Samuel
Published: June 2014

The mechanisms of fatigue crack initiation due to second phase particles are studied in 2050-T8 and 7050-T74 plate material. The particles in the specimens gauge lengths are imaged using SEM at the initial state. In 7050-T74, Mg2Si particles are very often cracked before any loading, whereas Al7Cu2Fe particles are not. In 2050-T8, the fraction of (Al, Cu, Fe, Mn) particles initially cracked is larger than that of Al7Cu2Fe in 7050-alloy, but lower than that of Mg2Si particles for similar sizes. For (Al, Cu, Fe, Mn) particles, the proportion of cracked particles increases when the modified shape ratio (aspect ratio including orientation versus rolling direction) increases. This effect is present but less pronounced for Mg2Si particles in 7050-T74. Fatigue cracks initiate at cracked (Al, Cu, Fe, Mn) particles in 2050-T8 alloy, and at both Al7Cu2Fe (cracked during cycling) and Mg2Si in 7050-T74 alloy.
Extrapolation of Creep Curve and Creep Rate by Strain Acceleration Parameter in Al-Mg Solid Solution Alloys
Authors: Sato Hiroyuki , Omote Kosuke , Sato Akira
Published: June 2014

It has been widely accepted that the creep characteristics at high temperatures are mainly evaluated by a minimum creep rate. Although, a shape of creep curve may vary depending on deformation conditions, the apparent steady state or minimum creep rates be the same. Thus,for detailed analysis and prediction of creep behavior, other values which reflect the shape of each creep curve should be considered. For the purpose, authors have proposed Sato’s strain- acceleration-parameter (Strain Acceleration and Transition Objective index, SATO-index) which reflects strain rate change during creep deformation. Based on the concept of SATO-index, the whole creep curve can be represented by a set of small number of numerical parameters, and can be extrapolated from a part of creep curve. In this paper, application of the concept of SATO-index to the creep curves of aluminum-magnesium solid solutions that the creep behavior of the alloys are well investigated and analyzed. The creep curve can be extrapolated by the concept from transient part of creep curve, and the extrapolated creep rates at the minimum creep rate agree well with experiment. Efficiency of the concept of SATO-index to creep experiments is pronounced.
Application of the Hybrid Metal Extrusion & Bonding (HYB) Method for Joining of AA6082-T6 Base Material
Authors: Aakenes Ulf Roar , Grong Øystein , Austigard Tor
Published: June 2014

In the present investigation the new HYB spindle extruder has been used for butt joining of 4 mm thick aluminium plates of the AA6082-T6 type at RT in one pass, employing a 1.6 mm diameter filler wire of matching composition. The test joint produced was subsequently sectioned and subjected to thorough examination in the laboratory, which included visual inspection of the surface quality and bead penetration depth, optical microscopy for visualisation and documentation of the material flow pattern and the microstructure within the joining zone and Vickers hardness testing. It is concluded that strict control of the bead penetration depth is necessary in order to obtain full bond strength. This is because the bead penetration determines the contact pressure between the filler metal and the base metal in the groove during filling.
Effect of Temperature Field and Pressure Force on the Inhomogeneity of 5754-H22 and 6082-T6 FSW Joints
Authors: Meilinger Ákos , Török Imre
Published: June 2014

The Friction Stir Welding (FSW) differs from the conventional welding process inter alia that the joint properties are not symmetric to the axis of joint line. Basically, it follows from the principle of the method because a rotary tool is used for welding. This asymmetry is due to created temperature field during welding, and the pressure force distribution along the thickness, so the investigation of these effects is important to create good quality welds.
Experiments were performed on FSW joints made of non-heat treatable (5754-H22) and heat treatable (6082-T6) aluminium alloys, because there are clear difference between the reacts to these effect and show different changing on the microstructure.
A special FSW tool was developed for the experiments and lowest inhomogeneity. Dynamic recrystallization and dynamic recovery can occur during welding so these were investigated by Gleeble material simulating system. During the experiments the grain sizes and grain shapes were also investigated.
SPH Analysis on Formation Manner of Wavy Joint Interface in Impact Welded Al/Cu Dissimilar Metal Plates
Authors: Nishiwaki Junto , Sawa Yuya , Harada Yohei , Kumai Shinji
Published: June 2014

The impact welding was performed for several kinds of metal plate couples. The joint interface exhibited a sinusoidal wave form when two metal plates with the same or similar density (e.g. Al/Al, Cu/Cu and Cu/Ni) were impact-welded by high-speed oblique collision. In contrast, as for dissimilar metal plate couples with large density difference such as Al/Cu, an asymmetric wavy interface was obtained. In order to make clear the reason for morphological difference, a computer simulation of the collision behavior was performed using SPH (Smooth Particle Hydrostatic) method. The simulation results revealed that the wave form was controlled by the interaction between the emitted metal jet and metal plate surfaces ahead of the collision point. For Al/Al and Cu/Ni, the emitted metal jet hit each surface alternatively and this resulted in symmetrical wavy interface formation. While, for Al/Cu, the metal jet was emitted to the direction parallel to the Cu plate, and the interaction took place between the metal jet and the Cu plate surface. The metal jet emission and wavy interface formation mechanism were also investigated.
Interfacial Reaction during Dissimilar Friction Stir Lap Welding of Aluminum Alloy to Stainless Steel
Authors: Ogura Tomo , Nishida Taichi , Takahashi Makoto , Nishida Hidehito , Fujimoto Mitsuo , Hirose Akio
Published: June 2014

A friction stir welded A3003 aluminum alloy /SUS304 stainless steel dissimilar lap joint was successfully produced. A sound joint that fractured at the base metal was obtained in the center region of the joint through the reaction layer of aluminum-rich intermetallic compounds with nanoorder thickness. The microstructural changes at the interface of the joint was examined by studying the hole left by the extracted welding tool produced at the end of the friction stir welding (FSW) bead using transmission electron microscopy (TEM). Mixed layers consisted of ultra-fined intermetallic compounds and stainless steel were observed. The stirred aluminum alloy flows onto the mixed layer after the tool transit and the joining was achieved. Based on the TEM observations, the joining process of the lap joint was also discussed.
Orientation Studies of α-Al(Fe,Mn)Si Dispersoids in 3xxx Al Alloys
Authors: Muggerud Astrid Marie Flattum , Li Yan Jun , Holmestad Randi
Published: June 2014

Dispersoids are important in 3xxx Al alloys, influencing mechanical properties, texture and recrystallization. In this work α-Al (Fe,Mn)Si dispersoids have been studied after low temperature homogenisation. The common orientation relationship between dispersoids and Al matrix has been reported in earlier studies. Here a systematic study on the orientation relationship and its exceptions is presented. It is found that most of the dispersoids follow the common orientation relationship, [1-1 1] α //[1-1 1]Al , (5-2 -7 ) α //(0 1 1)Al . Here the dispersoids are semi coherent with the Aluminum matrix. Different morphologies and habit planes are possible. Deviations from the most commonly observed orientation relationships are presented and discussed, to underline the complexity of the phase and its relation to the matrix.
Behaviour of Flow-Drilling Screw Connections
Authors: Sønstabø Johan Kolstø , Holmstrøm Petter Henrik , Morin David , Langseth Magnus
Published: June 2014

An experimental study on the behaviour and fracture of flow-drilling screw connections was carried out. Cross test specimens were used to study the deformation and fracture of the connections under different loading modes. For comparison, tests were also carried out on self-piercing rivet connections.
Effect of Heat Treatment Conditions on the Elongation of AA1200 Alloy Sheets
Authors: Asano Mineo , Nakamura Takuro , Yoshida Hideo
Published: June 2014

It has been reported that the elongation of the AA1050-H26 sheet annealed at 200°C is lower than that of the AA1050-H18 sheet. In this study, the effect of the annealing time at 250°C on the elongation of AA1200 alloy sheets was investigated, and the cause of the low elongation was discussed by observing the change in the microstructures before and after tensile deformation. The elongation of the samples annealed at 250°C for less than 50 min was below 1%, and this elongation was lower than the elongation of the as-rolled and annealed ones at 250°C for more than 150 min. In the samples annealed for a short time, the subgrains with diameters of 0.5~2μm formed, and Fe and Si, which were a solid solution, became segregated at the sub-boundaries. These samples were locally deformed in a stress concentrated area during the tensile deformation, and there was no significant increase in the dislocation density near the fracture part after the deformation. The cause of the low elongation was considered to be due to the dynamic recovery that locally occurred in a stress concentrated area during the tensile deformation, because dislocations introduced into the subgrains by the deformation easily moved to the sub-boundaries due to the low solute levels within the subgrains.
The Effect of Obstacle Strength Distribution on the Critical Resolved Shear Stress of Engineering Alloys
Authors: de Vaucorbeil A. , Poole Warren J. , Sinclair Chadwick W.
Published: June 2014

Line tension simulations were implemented to study the glide of a single dislocation through an array of randomly distributed point obstacles. The strength of each obstacle in the glide plane was populated from an assumed distribution, mimicking what might be expected in engineering alloys containing precipitates. The effect of changing the width of the distribution was investigated. It was found that the assumption of a uniform strength gives a lower bond to the critical resolved shear stress.
Activation Distance Determination of Rate Controlling Obstacles in the Age Hardening of a Quasi-Binary Al-Mg2Si Alloy
Authors: Diak Bradley , Lanerolle Rathna
Published: June 2014

The age hardening response of a quasi-binary Al-Mg2Si alloy was studied using activation distance analysis of precise strain rate sensitivity experiments at 78 and 300K. The alloy of Al-0.7Mg-0.33Si-0.024Fe-0.006Ti(at.%) has a stochiometrically balanced composition of Mg2Si. The alloy was solutionized at 550°C and ice water quenched before ageing in one of two ways: single-step or multi-step ageing. For single-step ageing: specimens were naturally aged for 70 days at room temperature (RT); pre-aged for 16 hours at 70°C; or artificially aged for 30 min or 10 hours at 175°C. For multi-step ageing: specimens were pre-aged at 70°C for 16 hours after natural ageing for 70 days at RT; artificially aged for 30 min or 10 hours at 175°C after pre-aging at 70°C for 16 hours; or artificially aged for 10 hours at 175°C after natural aging for 70 days at RT. The activation analysis reveals rate controlling obstacle dimensions ranging from 0.3 to 10 nm depending upon the ageing condition. A comparison is made to a prior three dimensional atom probe ageing study of the same alloy [Murayama and Hono, Acta Mater., 47 (1999) 1537-1578.].
Mechanical Properties and Constitutive Behavior of as-Cast High Strength AA7xxx Alloys below Solidus Temperature
Authors: Bai Qing Ling , Li Hong Xiang , Du Qiang , Zhang Ji Shan , Zhuang Lin Zhong
Published: June 2014

High strength AA7xxx alloys have been extensively used in aerospace industry. However, experience in cast house demonstrates that such alloys are particularly prone to cold cracking and ingot distortion during direct chill (DC) casting, which leads to big amount of scraping or even total rejection of ingot. Those stress induced defects are greatly affected by casting process, and fine tuning of casting parameters is critical to improve the quality and productivity. Recently, numerical modeling has been widely utilized in direct-chill casting for the purpose of thermal mechanical analysis and cracking evaluation. Parameter optimization has become convenient. The model needs the input of constitutive properties of the AA7xxx alloys, of which the microstructure should resemble those formed during DC casting. Unfortunately, these constitutive data are not yet available in literatures. In this study, the mechanical properties of two high strength AA7xxx alloys were measured at temperature range from solidus down to room temperature through on-cooling compressive tests and the effect of strain rate on stress-strain behavior was also studied. The results were fitted to extended Ludwik equation which has been proved to be able to properly describe the stress-strain response of aluminum alloys. The results of the current work shed some light on the evolution of mechanical behavior of high strength AA7xxx alloys during cooling from high temperature.
Mechanical Properties of Sintered of Al-5.5Zn-2.5Mg-0.5Cu PM Alloy
Authors: Rudianto Haris , Joo Jang Kwang , Sun Yang Sang , Jin Kim Yong , Dlouhy Ivo
Published: June 2014

In this research, Al-5.5Zn-2.5Mg-0.5Cu was investigated. Compaction pressure at 700 MPa was carried out to make green body materials. Strong interlocking between particles is expected after high compaction process. Sintering of aluminum composites powder is sensitive to the humidity. High purity nitrogen gas was used to sinter this material from 560o-585°C for 1 hour. Sintering density increased with increasing sintering temperature and reached 96% relative sintering density at 580°C. Mechanical properties investigation of this material was done with hardness and tensile test. At optimum sintering conditions, this material has 40 HRB hardness and 329 MPa tensile strength. Based on chemical composition, this material has possibility to improve mechanical properties by T6 heat treatment. Strengthening precipitates such as MgZn2 and CuAl2 were expected as results from T6 heat treatment. Mechanical properties improved with this treatment with reaching 513 MPa of tensile strength. SEM, DSC-TGA and X-Ray Diffraction were used to characterize this material.
Metallographic Methods for Oxide Skin Segregation Studies
Authors: Simensen Christian J. , Fossheim Harry , Sæter Jan Anders
Published: June 2014

This work is a study of the segregation of alloying elements and salts to the surface of Direct Chilled-cast (DC-cast) ingots of alloy: (i) AA5083; and (ii) AA5182. The ingots only have slightly different chemical compositions. Alloy AA5182 contains Cu, while alloy AA5083 is grain refined, contains Cr, and is lower in Si and Fe compared to AA5182. The ingot microstructures were investigated using Optical Microscopy, Scanning Electron Microscope (SEM) and Secondary Ion Mass Spectrometry (SIMS).
The results showed that the surfaces contained aluminum dendrites, large intermetallic crystals (Al6(MnFe) and Al3(Fe,Mn)) and impurities, and small crystals between dendrite arms. Between the dendrites small salt crystals containing Na, K, Ca, Mg, F and/or Cl were found. The conclusion is that salt and minority impurities are mainly located to grain boundaries in the segregation zone.
Influence of Temperature and Strain Rate on the Mechanical Behaviour of Aluminium Alloy AA6060
Authors: Vilamosa Vincent , Clausen Arild H. , Hopperstad Odd Sture , Børvik Tore , Skjervold Svein
Published: June 2014

In an attempt to improve the constitutive models for 6xxx aluminium alloys at high temperatures and high strain rates, a comprehensive test series has been carried out for AA6060. Uniaxial tension tests were performed at various strain rates from 0.01 s-1 to 1000 s-1 and temperatures from 20 °C to 350 °C. The tests were carried out using a standard tensile machine for low to moderate strain rates and a split-Hopkinson tension bar (SHTB) system for high strain rates. In both cases, an induction apparatus was used to heat the sample while local deformation measurements were obtained with a high-speed camera and used to estimate the true strain beyond necking. Strong coupling between the influence of strain rate and temperature on the stress-strain behaviour was found. At room temperature, the strain rate has a minor effect on the behaviour of AA6060. On the other hand, a significant increase of the yield stress and work-hardening with strain-rate is observed for temperatures above (K), being the melting temperature; i.e., above 673 K.
A Super-Ductile Alloy for the Diecasting of Aluminium Automotive Body Structural Components
Authors: Watson Douglas , Ji Shouxun , Fan Zhong Yun
Published: June 2014

Super-ductile diecast aluminium alloys are critical to future lightweighting of automotive body structures. This paper introduces a diecast aluminium alloy that can satisfy the requirements of these applications. After a review of currently available alloys, the requirement of a diecast aluminium alloy for automotive body structural parts is proposed and an Al-Mg-Si system is suggested. The effect of the alloying elements, in the composition, has been investigated on the microstructure and mechanical properties, in particular the yield strength, the ultimate tensile strength and elongation.
Tensile Properties of 7075 Aluminum Alloys Subjected to Pre-Fatigue in Humid Environment
Authors: Yamada Hiroyuki , Tsurudome Masaki , Ogasawara Nagahisa , Horikawa Keitaro
Published: June 2014

The tensile properties of the quasi-static and the impact tests for 7075 aluminum alloys subjected to pre-fatigue deformation in a humid environment were investigated. An impact tensile test of the pre-fatigue deformed specimens was performed by means of the Split Hopkinson pressure bar method. Within the authors set of experiments, the flow stress in both the quasi-static and the impact tests was unaffected by the pre-fatigue deformation. On the other hand, it was shown that the ductility of the pre-fatigue specimen was slightly lower than that of the non-fatigue specimen. Additionally, the pre-fatigue specimen in a high-humidity environment had a lower ductility than in a low-humidity environment. The ductility of the quasi-static test was decreased as compared with the impact test. It is thought that the ductility loss occurred due to changes in the microstructure, such as dislocations caused by the presence of hydrogen in the specimen due to pre-fatigue deformation in a high-humidity environment.
Fundamentals of Bending AA6xxx Sheet
Authors: Mattei Laurent , Klocker Helmut , Daniel Dominique , Guiglionda Gilles , Driver Julian
Published: June 2014

This paper describes recent experimental results on the strain distributions developed during bending of AA6xxx sheet for automotive applications, together with a new model for the mechanics and metallurgy of strain localization during bending. A detailed microscopic study (optical and SEM/EBSD) shows that damage development during bending to strains of order unity is controlled by through-thickness shear banding at the grain scale. A new finite element microstructure-based model is introduced to predict this strain localization during practical bending. The sheet metal is modelled as a grain aggregate, each grain having its own flow stress. After validation, the model is applied to the experimental results through an analysis of the critical plastic strain at the outer surface during bending of AA6016 sheet alloys. It correctly describes the respective influences of sheet thickness, grain size and shape, and work hardening. In particular the model brings out the primary importance of large-strain hardening and the spread of the flow stress distribution.
Crystal-Plasticity Simulation of the Evolution of the Matt Surface in Pack Rolling of Aluminium Foil
Authors: Engler Olaf , Laptyeva Galyna , Aretz Holger , Nitzsche Gernot
Published: June 2014

Aluminium foil is rolled double-layered during the final rolling pass. When the sheets are later separated, the inside surface is dull and the outside surface is shiny. The matt inner side is characterized by significant surface corrugations which are believed to be a precursor for the initiation of fracture upon a subsequent forming operation. Therefore, understanding of the development of the matt side of Al foil will help to control and, eventually, improve the properties of Al foil.
It was the goal of the present study to correlate the development of the matt side with the spatial arrangement of the crystallographic orientations of the foil rolling texture. This approach builds on a recent project to correlate the phenomenon of roping in AA 6xxx alloy sheet for car body applications to the occurrence of band-like clusters of grains with similar crystallographic orientation. Large-scale orientation maps obtained by electron back-scattered diffraction (EBSD) were input into a visco-plastic self-consistent crystal-plasticity model to analyse the strain anisotropy caused by the spatial distribution of the various rolling texture components. The new model is applied to several Al foils with different characteristics of the matt side.
Slip System Interaction Matrix and its Influence on the Macroscopic Response of Al Alloys
Authors: Khadyko Mikhail , Dumoulin Stéphane , Hopperstad Odd Sture
Published: June 2014

In numerical models based on the crystal plasticity theory, various rules are implemented to describe hardening on the slip system level. The rules used are often variations of the Mecking-Kocks law, where the statistically stored dislocation density is the single internal variable. The dislocation density evolution equation consists of two terms representing accumulation and annihilation of dislocations. The accumulation term depends on a scalar parameter and an interaction matrix, which describes the contribution of all slip systems to the accumulation of the dislocations on a given slip system. Physically this matrix represents the relative strength of various dislocation locks which form when dislocations from different slip systems interact. The numerical values of the elements of the interaction matrix are rather hard to establish, but this has been done experimentally for different alloys and also based on numerical simulations. The obtained values, found in literature, are very different from each other. We use some new experimental data in an attempt to establish the influence of the numerical values of the elements of the interaction matrix on the hardening of a polycrystal.
Effect of Aging Precipitates on the Bendability of an Al-Mg-Si Alloy
Authors: Nakanishi Hidetaka , Asano Mineo , Yoshida Hideo
Published: June 2014

Al-Mg-Si alloys are usually applied a T4 temper as the plate material for automobile bodies due to the necessity of a high bake hardening property. Many reports about the improvement in the bendability of Al-Mg-Si alloys applied a T4 temper have been published, because they easily crack during the hemming process. On the other hand, Al-Mg-Si alloys applied T6 and T7 tempers are used as the material of wiring plates and heat radiation devices. A high electrical conductivity and good bendability are necessary for these devices. In this study, the effect of the aging conditions on the bendability was investigated. As a result, the bendability at the T6 temper significantly decreased. The bendability under the aging temper, and over the aging temper was better than that at the T6 temper. Samples treated by natural-aging at high temperature before the T6 temper easily cracked during the bending test. It was postulated that the formation of shear bands was significant and the bendability decreased during the bending test under the high density and fine β phase precipitate conditions.
Atomic-Resolution Elemental Mapping of Precipitates in a 7449 Aluminium Alloy
Authors: Wenner Sigurd , Marioara Calin Daniel , Lefebvre Williams , Ramasse Quentin M. , Kepaptsoglou Despoina Maria , Hage Fredrik S. , Holmestad Randi
Published: June 2014

The high-strength weldable 7xxx series of aluminium alloys are of great importance to the aeronautics industry. Only recently, the complex structures of the AlZnMg hardening precipitates have been solved by HAADFSTEM imaging and first-principles calculations. However, perfect models of precipitate structures are often insufficient as several elements may be mixed into precipitate compositions. We have investigated this effect by STEMEELS spectrum imaging with an aberration-corrected microscope. In a 7449 alloy, Cu and Al were found to replace atoms at certain sites in both metastable and equilibrium ZnMg precipitates.
Through-Process Modeling of Microstructure Development during Multi-Pass Hot Deformation Including Partial Recrystallization
Authors: Jiao Feng , Mohles Volker , Miroux Alexis , Bollmann Christian
Published: June 2014

During reversible break-down hot rolling, recrystallization can take place during inter-pass annealing and even after the final pass, because the material is kept at high temperature throughout the process. A partially recrystallized microstructure is quite often obtained during inter-pass annealing and is the starting state for the subsequent rolling pass. This is in particular the case when fine particles are already present or have just precipitated in the microstructure. The particles can pin the moving grain boundaries in the hot deformed material with low energy stored during deformation. To transfer the partly recrystallized microstructure from the recrystallization model to the deformation model for simulation of the subsequent pass, a new link method has been developed for multi-pass through-process modeling. This method allows a direct data flow between the deformation model GIA-3IVM+ and the recrystallization model CORe. This new model framework was used to simulate the microstructure evolution during break-down hot rolling of precipitates containing alloy AA6016. The predicted microstructure agrees well with experimental observations.
Prediction of Yield Strength at Room Temperature for Squeeze Cast A226
Authors: Falahati Ahmad , Kumar Manoj , Just Michael
Published: June 2014

Predicting yield strength of the cast is difficult, mainly due to inherent chemical inhomogeneity of the microstructure and metal matrix composite nature of the cast. In our approach to predict the yield strength of as cast material AlSi9Cu3(Fe), Scheil-Gulliver model has been used to calculate the phase fraction and chemical composition of each phase during solidification and at each temperature step. Inhomogeneity of the microstructure has been taken into account by considering the evolution of pre-eutectic and eutectic fractions separately. The solidification time-temperature data and cooling to room temperature are recorded using thermocouples and serve as input for the thermo-kinetic software “MatCalc”, that has been used for Scheil simulation and takes into account the evolution of microstructure after solidification and during any arbitrary cooling rate. The strengthening model takes into account the contributions of the intrinsic yield strength of the aluminum matrix, solid solution strengthening, precipitation hardening, effect of eutectic silicon portion and dendrite arm spacing size effect. The phases taken in to consideration include α-Al, Intermetallics, Si and Cu-rich precipitates. The predicted yield strength values are validated by comparing with the experimental values. This approach is extendable to calculate yield strength of the as-cast and heat-treated aluminum alloys.
The Effect of Hot Deformation on Dispersoid Evolution in a Model 3xxx Alloy
Authors: Robson Joseph D. , Hill Thomas , Kamp Nicolas
Published: June 2014

The influence of hot deformation on the evolution of size, shape, and fraction of dispersoids has been studied in a simple 3xxx aluminium alloy by means of hot torsion testing. It has been shown that at high strain rates, deformation leads to spheroidization of the dispersoids, an increase in number density, and an increase in volume fraction. The increase in number density and volume fraction are associated with precipitation of new particles. The enhancement of manganese diffusion is a key factor in promoting rapid dispersoid evolution during deformation. A model has been developed to estimate the effect of deformation induced vacancies and dislocations on diffusion. This predicts that an order of magnitude increase in diffusion coefficient between may occur under typical hot deformation conditions, consistent with the rapid microstructural changes measured experimentally.
Analysis of the Rate of Recovery and Recrystallization in Pure Aluminum by a New Rate Equation
Authors: Yoshida Hideo , Ookubo Yoshimasa
Published: June 2014

A new rate equation developed by Yamamoto was applied to the rate of recovery and recrystallization in pure aluminum. The entire reaction can be expressed by Yamamoto’s equation because it contains the term of particle number. By applying this equation, the entire reaction process was divided into two reactions, the recovery and recrystallization. The obtained values of the time-exponent are 0.5 in the former and 1 in the latter regardless of the soaking conditions and annealing temperatures. Based on the microstructures and time-exponents, it is concluded that the rate of recovery and recrystallization is controlled by the precipitation of silicon on the dislocation cell boundaries during the recovery process and the precipitation of iron on the subgrain boundaries during the recrystallization one.
Mechanical Milling of Quasicrystalline Al-Cu-Fe Alloys
Authors: Bryantsev Pavel , Samoshina Marina
Published: June 2014

Ingots of alloys Al-Cu-Fe were obtained by casting in a graphite mold. Mechanical milling of alloy particles in the as-cast state and after homogenization annealing was carried out in planetary ball mill Retsch PM400 in an argon atmosphere. As a result of mechanical milling granules with an average size of 35-40 μm and fine internal microstructure are formed. The size of coherent scattering regions in quasicrystalline phase after mechanical milling was about 10-15 nm. Mechanical milling after homogenization heat treatment allows much refines the quasicrystalline phase than in the case of mechanical milling of cast alloy.