bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of an Integrated Care Model for Kidney Disease in the Development of Peritoneal Dialysis: A Single-Center Experience in China
Authors: Zhang Xiaohui , Shou Zhangfei , Chen Zhimin , Xu Ying , Han Fei , Yin Xiaohong , Lin Jun , Pan Haiyan , He Peipei , Chen Jianghua
Published: June 2014

Peritoneal dialysis plays a crucial role in the integrated care of patients with end-stage renal disease (ESRD). In this paper, we retrospectively analyzed the quality indicators of peritoneal dialysis (PD) in 712 patients from our center who underwent PD between 2004 and 2011. In 43% of patients, follow-up was undertaken every 3 months at our outpatient department, and 54% patients were followed up by both our hospital and other local hospitals. The patient survival rate at 1, 3 and 5 years was 96.3%, 85.4% and 76.2%, respectively. The technique survival (excludes death/transplantation) at 1, 3 and 5 years was 95.1%, 87.7% and 79.6%, respectively. Fluid overload occurred in 29.2% of patients and was one of the major reasons for discontinuing PD. The peritonitis rate in our center decreased to 0.16 episodes/year in 2011. In addition, since our center is one of the largest integrated-treatment centers for ESRD in China, we have developed a multilevel care program in Zhejiang Province, which resulted in rapid growth of PD in our province in recent years.
MODELLING AND SIMULATION OF DISPERSIONS OF POWDER EMISSIONS FROM MULTIPLE SOURCES WITH THE MATHEMATICAL MODEL POL 15SM
Authors: Budianu Mihaela , Nagacevschi Valeriu , Macoveanu Matei
Published: June 2014

Over the last decades, air pollution has become one of the greatest challenges negatively affecting human health and the entire environment, including air, water, soil, vegetation, and urban areas. Lately, special attention has been given to mathematical modelling for diffusion of pollutants in the atmosphere as a particularly effective and efficient method that can be used to study, control and reduce air pollution. The diversity of models developed by different research groups imposed a rigorous understanding of model types in order to apply them correctly according to local or regional problems of air pollution phenomenon. Tus the authors have developed and improved two mathematical models for dispersion of air pollutants. Tis paper presents a case study of dispersion of powders in suspension originating from 14 point sources that correspond to 5 economic agents in the agroindustrial area of Vaslui city using a computer simulation based on the mathematical model Pol 15sm, for multiple point sources of pollution, designed by the authors.
DYNAMIC INTERACTION BETWEEN HOUSE PRICES AND STOCK PRICES IN MALAYSIA
Authors: Lean Hooi Hooi , Smyth Russell
Published: June 2014

This paper examines the dynamic linkages between house price indices, interest rates and stock prices in Malaysia using cointegration and Granger causality testing. For Malaysia as a whole, we find that house prices, stock prices and interest rates are not cointegrated. For Kuala Lumpur, Penang and Selangor we find that house prices, stock prices and interest rates are cointegrated for 40% of the house price indices. When there is evidence of cointegration in these regions, we find that stock prices lead house prices. While there are alternative potential reasons for this finding, such as slow adjustment of house prices in response to a shock in the fundamentals, it is consistent with a wealth effect. A likely explanation for this result is that in these states, compared with the Malaysian average, housing is expensive, income is high and real estate is used much more as an investment vehicle by both wealthy Malaysians and foreigners leveraging of the share market.
INQUIRY INTO VERTICAL MOVEMENTS OF THE EARTH‘S CRUST BASED ON SAMPLES FROM EASTERN LITHUANIA
Authors: Puziene Ruta , Anikeniene Asta , Karsokiene Gitana
Published: June 2014

In the research of vertical movements of the earth’s crust, examination of statistical correlations between the measured vertical movements of the earth’s crust and territorial geo-indexes is accomplished with the help of mathematical statistical analysis. Availability of the precise repeated levelling measuring data coupled with the preferred research methodology offer a chance to determine and predict recent vertical movements of the earth’s crust. For the inquiry into recent vertical movements of the earth’s crust, a Lithuanian class I vertical network levelling polygon was used. Drawing on measurements made in the polygon, vertical velocities of earth’s crust movements were calculated along the following levelling lines. For determining the relations shared by vertical movements of the earth’s crust and territorial geo-parameters, the following territory-defining parameters are accepted. Examination of the special qualities of relations shared by vertical movements of the earth’s crust and geo-parameters in the territory under research contributed to the computation of correlation matrices. Regression models are worked out taking into consideration only particular territory-defining geo-parameters, i.e. only those parameters which exhibit the following correlation coefficient value of the vertical earth’s crust movement velocity: r ≥ 0.50. A forecast of the velocities pertaining to vertical movements of the earth’s crust in the territory under examination was made with the application of regression models. Further in the process of this research, a map was compiled specifying the velocities of vertical movements of the earth’s crust in the territory. In the eastern part of this territory, the earth’s crust rises at a rate of up to 3 mm/year; while in the western part of it, the earth crust lowers at a rate of up to –1.5 mm/year. In order to pinpoint territories characterised by temperate and regular rising/lowering or intensive rising/lowering, a map of horizontal gradients of recent vertical earth crust movements in the territory enclosed by levelling polygon was compiled.
Symbiota – A virtual platform for creating voucher-based biodiversity information communities
Authors: Gries Corinna , Gilbert Edward , Franz Nico
Published: June 2014

We review the Symbiota software platform for creating voucher-based biodiversity information portals and communities. Symbiota was originally conceived to promote small- to medium-sized, regionally and/or taxonomically themed collaborations of natural history collections. Over the past eight years the taxonomically diverse portals have grown into an important resource in North America and beyond for mobilizing, integrating, and using specimen- and observation-based occurrence records and derivative biodiversity information products. Designed to mirror the conceptual structure of traditional floras and faunas, Symbiota is exclusively web-based and employs a novel data model, information linking, and algorithms to provide highly dynamic customization. The themed portals enable meaningful access to biodiversity data for anyone from specialist to high school student. Symbiota emulates functionality of modern Content Management Systems, providing highly sophisticated yet intuitive user interfaces for data entry, batch processes, and editing. Each kind of content provision may be selectively accessed by authenticated information providers. Occupying a fairly specific niche in the biodiversity informatics arena, Symbiota provides extensive data exchange facilities and collaborates with other development projects to incorporate and not duplicate functionality as appropriate.
The individual and the actuation of sound change
Authors: Stevens Mary , Harrington Jonathan
Published: June 2014

This paper reviews current experimental approaches to sound change. An ongoing challenge in sound change research is to link the initiation of sound change within individual cognitive grammars to the diffusion of novel variants through the community. The articulatory and perceptual phonetic forces that bring about the pre-conditions for sound change and that explain its directionality are always present in the transmission of spoken language, yet sound systems are remarkably stable over time. This paper describes how recent approaches to the actuation problema converge on the idea that variability between individuals may be the key to understanding how some synchronic variation can become sound change. It then reviews the evidence for individual differences based on four areas of phonetic research (speech production, speech perception/cognitive processing, the perception-production link, and linguistic experience and imitation). This evidence suggests that differences between individuals may help to explain why sound change is so rarely actuated even though the phonetic pre-conditions are constantly being generated in spoken language interactions.
What is computational phonology?
Authors: Daland Robert
Published: June 2014

Computational phonology is not one thing. Rather, it is an umbrella term which may refer to work on formal language theory, computer-implemented models of cognitive processes, and corpus methods derived from the literature on natural language processing (NLP). This article gives an overview of these distinct areas, identifying commonalities and differences in the goals of each area, as well as highlighting recent results of interest. The overview is necessarily brief and subjective. Broadly speaking, it is argued that learning is a pervasive theme in these areas, but the core questions and concerns vary too much to define a coherent field. Computational phonologists are more united by a shared body of formal knowledge than they are by a shared sense of what the important questions are.
Measuring a decade of progress in Text-to-Speech
Authors: King Simon
Published: June 2014

The Blizzard Challenge offers a unique insight into progress in text-to-speech synthesis over the last decade. By using a very large listening test to compare the performance of a wide range of systems that have been constructed using a common corpus of speech recordings, it is possible to make some direct comparisons between competing techniques. By reviewing over a hundred papers describing all entries to the Challenge since 2005, we can make a useful summary of the most successful techniques adopted by participating teams, as well as drawing some conclusions about where the Blizzard Challenge has succeeded, and where there are still open problems in cross-system comparisons of text-to-speech synthesisers.
De arrieros a mercaderes. Orígenes de los comerciantes de la región Tacna-Arica, 1776-1794
Authors: Rosenblitt B. Jaime
Published: June 2014

Este artículo analiza los efectos de las reformas borbónicas en el partido de Arica, en el Virreinato del Perú, y examina el contexto económico que generaron, a partir del cual algunas personas dedicadas al transporte lograron convertirse en pequeños comerciantes.
De la indiferencia a la resistencia. Los sectores populares y la Guerra de Independencia en el norte de Chile (1817-1823)
Authors: Goicovic Donoso Igor
Published: June 2014

El proceso de Independencia en Chile fue liderado por la élite criolla terrateniente y mercantil radicada en Santiago y en sus inmediaciones. La posterior etapa de construcción del Estado y de la nación fue expresión de su proyecto político. No obstante, los sectores populares constituidos por peones, artesanos y labradores, esclavos e indígenas, se mantuvieron ajenos a esta propuesta y, en el contexto de la desorganización de la sociedad colonial, desplegaron estrategias de autonomización social y política. Expresión de ello fueron las montoneras, el bandolerismo y la deserción. Este artículo analiza el desarrollo de estos fenómenos en el norte de Chile entre 1817 y 1823.
México y las instituciones republicanas en el exilio: del apoyo del Cardenismo a la instrumentación política del Partido Revolucionario Institucional, 1939-1977
Authors: De Hoyos Puente Jorge
Published: June 2014

Este artículo realiza una revisión de las circunstancias del apoyo de los sucesivos gobiernos mexicanos hacia la II República en el exilio a lo largo de la dictadura franquista. Esta ayuda supuso uno de los principales balones de oxígeno para la legalidad republicana en el exilio, no exenta, sin embargo, de mitificaciones. Pretendemos abordar algunas de las principales claves para entender esa actitud sostenida en el tiempo por parte de las autoridades mexicanas.
Using a Task-Based Approach for Supporting a Blended Learning Model for English as a Foreign Language
Authors: Ferreira Anita Ferreira , Salinas Jaime García , Morales Sandra
Published: June 2014

As Computer-Assisted Language Learning (CALL) has taken an important role in foreign language teaching and learning, not only is concrete data about the usefulness of technology- mediated environments for these purposes necessary, but also how the learning process is improved in such environments when learner training for CALL. The objective of this paper is to present an investigation which sought to explore empirical evidence regarding the effectiveness of a blended learning model, and also the use of language learning strategies in this kind of learning environment in order to increase its methodological potency with language learners. Consequently, this paper shows the findings of 2 experimental studies which aimed to provide data on (1) the efficiency of a blended learning (BL) model for language teaching and learning which combined task-based instruction, cooperative learning and optimal methodological principles for online learning (Doughty & Long, 2003), and (2) the use of learner training strategies for CALL in order to support and enhance the language learning process in this blended learning environment. The results from both studies suggest that the experimental group improved their language proficiency when compared to the control group. As a result, it is possible to conclude that (1) the blended learning design that included online tasks and cooperative instruction was beneficial for the development of language skills and (2) the use of learner training strategies for the blended learning model was highly beneficial for the students' language learning experience.
Evaluation of Dynamic Deformation Properties of Metallic Materials with Different Crystal Structures Using Taylor Impact Test
Authors: Bae Kyung Oh , Shin Hyung Seop , Huh Hoon , Park Lee Ju , Kim Hyung Won
Published: June 2014

Investigations on dynamic deformation behavior of metallic materials under high strain rate have been conducted. In this study, the deformation behaviors of metallic materials with different crystal structures were examined through Taylor impact test. As representative materials, HSA800 (body-centered cubic: BCC), OFHC (face-centered cubic: FCC) and Ti-6Al-4V (hexagonal close-packed : HCP) were adopted. Taylor impact tests were carried out in the impact velocity range of 100~270 m/s for BCC and FCC materials and 150~330 m/s for Ti-alloy one. In addition, an 8-Ch high-speed photography system was used to provide a series of images representing the plastic deformation behavior of a projectile during Taylor test. The dynamic yield strength and the strain rate were calculated based on the contact time duration of projectile determined from high-speed images. From the result, the strain rate dependency of the dynamic yield strength varied depending on the material adopted. Bulging occurred at the impact part was more significant in FCC material than in BCC one, while a shear band occurred in the Ti-alloy specimen when the impact velocity of projectile exceeded 270 m/s.
Joining Experiment of Aluminum Sheets Using High-Speed Shearing
Authors: Yamashita Minoru , Tezuka Tatsuya , Hattori Toshio
Published: June 2014

A novel method for joining of sheet edges was investigated. It makes use of the sheared faces under high-speed. The temperature remarkably elevates and the material softens in the thin severely deformed layer. The cut faces are contacted each other with sliding motion immediately after shearing. Sheet materials are a pure aluminum A1050 and its alloy A5052. Two similar sets of circular shearing punch, die and sheet are concentrically stacked in the device for performing the simultaneous shearing. The upper sheared circular sheet slides into the hole of the lower one for joining shortly after the shearing. Strain-rate order was about 104/s in shearing, where the punches were driven by a drop-weight. Quasi-static test was also conducted for comparison. Joining was achieved only in the high-speed test. Joining boundary was not visible at the central portion in thickness, though the gap openings were seen near both sheet surfaces. Joining efficiency was evaluated as the relative strength to the tensile strength of the material. It was improved as the shearing clearance becomes smaller. The maximum efficiency was about 30 % for A1050 material. It is about 25 % for A5052. It was at most 10 % in the joining of A1050 and A5052.
Response of Filled Thin-Walled Square Tubes to Axial Impact Load
Authors: Yuen Steeve Chung Kim , Nurick Gerald , Piu Sylvester , Ebrahim Gadija
Published: June 2014

This paper presents the results of an investigation into the response of thin-walled square (60x60 mm and 76x76 mm) tubes made from mild steel filled with four different fillers; aluminium foam (Cymat 7%), two types of aluminium honeycomb and polyurethane foam to quasi-static and dynamic axial impact load. The energy absorption characteristics of the foam-filled tubes are compared to that of a hollow tube, through efficiency calculations. The tubular structures are subjected to axial impact load generated by drop masses of 320 kg and 390 kg released from a height ranging between 2.1 m to 4.1 m. Footage from a high speed camera is used to determine the average crush forces exerted by each specimen. The results show that the fillers have insignificant effects on the initial peak forces based on the quasi-static results but increase the overall mean crushed force. The findings also indicate that the fillers affect at times the size of the lobe formed thus compromising the energy absorption capacity of the tube.
Experimental Evaluation of Dynamic Buckling Load of GFRP Rod for Gas Circuit Breaker
Authors: Hashimoto H. , Yaka H. , Riku I , Umeda T. , Mimura K.
Published: June 2014

Dynamic elastic buckling behaviors of GFRP and Aluminum rods were experimentally investigated. In a gas circuit breaker of an electric power substation, an operating rod consisting of insulating materials is connected to an interrupter. The rod securely insulate between the interrupter and an operating mechanism. The rod is configured with a slender rod made of Glass Fiber Reinforced Plastics (GFRP). When the gas circuit breaker ends the opening operation, impulsive compression load acts on the GFRP rod. To develop a smaller and lighter GFRP rod, dynamic buckling loads of the rod must be studied. In this study, dynamic elastic buckling loads for slender GFRP and aluminum rods were investigated by an experimental method. The drop weight impact tests of the GFRP rods and aluminum rods were employed. In the testing device, a special load cell called the “Load Sensing Block” was used to measure the dynamic load of long time duration. Slender GFRP rods with various lengths were axially loaded at the impact velocities ranging from 0.75m/s to 4.5m/s. From the experimental results, an empirical criterion for the dynamic buckling load of the GFRP rod was proposed in terms of the impact velocity and the slenderness ratio. Furthermore, results showed the proposed criterion could successfully describe the buckling behavior of not only the GFRP rod but also the aluminum rod.
The Synergistic Effect of Thiourea and Surfactants on Corrosion Inhibition of Stainless Steel-316 in Hydrochloric Acid
Authors: Ullah Sami , Nadeem Muhammad , Azmi Mohd Shariff , Ahmad Faiz , Shahid Shaukat Ali , Sagir Muhammad , Raza Malik Muhammad Rafi , Mushtaq Muhammad
Published: June 2014

Corrosion and scaling are the common problems to all the industries. A remedy of these problems was sought out through chemical treatment: indigenously available raw materials including thiourea, surfactants (cationic, anionic and nonionic containing pre, critical and post micellar concentration). Evaluation of corrosion inhibition properties stainless steel 316 by thiourea based inhibitor and its synergistic effect with cationic cetyl tri-methyl ammonium bromide (CTAB), anionic sodium dodecyl sulphate (SDS) and nonionic triton X-100 have been carried out by weight loss method as a function of concentration of thiourea and surfactants. These materials were applied to the coupons of stainless steel 316 in different acidic concentration. Corrosion rates were calculated using weight loss method. Excellent results were achieved regarding corrosion inhibition in the presence of thiourea and surfactants assuring the better performance of these chemicals. The results showed that corrosion rate was decreased from 90 mpy to 12.1 mpy after 720 hours by the addition of 200ppm thiourea in critical micellar concentration of SDS in 3M HCl acid solution.
Ultrasonic Melt Processing: Opportunities and Misconceptions
Authors: Eskin Dmitry G.
Published: June 2014

Ultrasonic melt processing enjoys the revival of interest in the last 1015 years. Although the main fundamental works as well as lab-scale and pilot-scale demonstrations date back to the 1950-1980s, the ultrasonic melt processing of light metals has not become a major technology. Recently the deficiencies of current technological approaches brought back the interest to ultrasonic treatment for degassing, grain refinement and composite materials. The current attempts to repeat the earlier results, to gain more fundamental insight using advanced means available and to up-scale the positive effects to the industrial scale show frequent lack of understanding of the basic controlling mechanisms. This paper describes the main mechanisms of ultrasonic melt processing, shows frequent mistakes, and gives some guidelines for technology up-scaling. The paper is illustrated with the latest experimental results.
Investigation of the Precipitation Kinetics of a New Al-Mg-Sc-Zr Alloy
Authors: Taendl Johannes , Palm Frank , Anders Kevin , Gradinger Rudolf , Poletti Cecilia
Published: June 2014

This study investigates the precipitation behavior of two similar cast Al-Mg-Sc-Zr alloys with different solidification and cooling rates. Microstructural analyses and hardness testing were performed after casting and ageing. In addition, the precipitation and hardness evolution after rapid quenching using electron beam re-solidification were studied. It was shown that the amount of Al3(Sc,Zr) phases present after casting or re-solidification increases with decreasing solidification and cooling rate. Consequently, the degree of supersaturation in Sc and Zr at room temperature and thus the hardening potential in a subsequent ageing process increases with the solidification and cooling rate. Therefore, the electron beam re-solidified samples revealed the most pronounced hardening.
Salt Free Treatment of Aluminium Dross
Authors: Jensen Roar , Syvertsen Martin
Published: June 2014

Aluminium dross is composed of metallic aluminium and non-metallic compounds such as oxides, nitrides and carbides. The dross created during primary and secondary aluminium production can amount up to 1% of the total tonnage and may contain up to 90% aluminium metal. The conventional procedure for dross treatment is to use salt for separating the metallic aluminium and the non-metallic compounds. The resulting salt cake has to be processed further. This paper describes a process using a plasma rotary furnace with a non-oxidizing atmosphere and heated by a graphite plasma torch to separate the aluminium from the non-metallic compounds. A pilot scale furnace (charge 500kg) has been designed and tested. In the experiment presented here a mixture of aluminium and aluminium dross were charged into the furnace. Good atmosphere control was maintained during the experiment. No wear on the refractory and only minor wear on the graphite electrodes was observed after the experiment. The result shows that 98.9% of the aluminium in the charged raw materials was recovered in tapped metal without using any salt anywhere in the process. The aluminium metal tapped from the process had only minor increase in the trace elements compared to the metal originally produced. The inclusion content in the metal was also not increased significantly. The residual non-metallic compounds should be possible to recycle in the electrolysis or used in the cement industry.
Oxidation of Manganese-Containing Aluminum Alloys Studied by SEM
Authors: Wilson Shawn C. , Kvithyld Anne , Engh Thorvald Abel , Tranell Gabriella
Published: June 2014

During remelting of aluminum manganese-containing alloys, some industrial experience has indicateda tendency toward increased oxidation losses when compared to unalloyed Al. A goal of thiswork is to increase current knowledge of oxidation of Mn-containing aluminum. An oxidation studywas performed on 99.99% Al, Al-1%Mn and Al-5%Mn materials in a muffle furnace in air. Theseoxidized materials were analyzed in the Scanning Electron Microscope using Energy Dispersive xraySpectroscopy (EDS) both for chemical composition and to analyze the structure of the oxide thatwas formed. The main findings from the SEM analysis of the oxidized 99.99% Al, Al1%Mn andAl5%Mn materials are: 1) The oxides formed on the Al1Mn and Al5Mn materials contained onlyminute amounts of Mn. However, small clusters of Mn metal were found among the Al2O3 particleson the surface of the Al1Mn and Al5Mn samples. 2) Dissolved Mn increased from the surface to theinterior, and Mn-rich particles were present in the interior of the Al1Mn and Al5Mn samples. 3) Theoxide layer thickness increases with Mn content, and the oxide film is more fragmented.
Study on Absorption Rate of Phosphorus for Hypereutectic Al-Si Alloy Modified with Cu-P
Authors: Zhong Gu , Wu Zhi Bin , Qiu Chu , Li Ya Fang , Nagaumi Hiromi
Published: June 2014

In this paper, the effects of process parameters on the absorption rate of P for hypereutectic Al-Si alloy (A390) which modified with Cu-14%P master alloy were systematically studied. And the mechanism that the process parameters play a role in effecting on the absorption rate of P was deeply investigated. The results indicated that the absorption rate of P increased with the increase of modified time and temperature, and decreased with the increase of the amount of added P. Under the same process condition, P added in form of Cu-14%P particles can cause to obtain the higher absorption rate of P than that of Cu-14%P powders. According to the experimental results, an equation on changes of the absorption rate of P was proposed, and the results show that good agreement is obtained between calculated and experimental values. The process parameters played a role in effecting on the absorption rate of P mainly through affecting the reaction rate of forming AlP particles in the melt, as well as the degree of reaction reached.
Microstructural Evolution during Isothermal Annealing of a Cold-Rolled Al-Mn-Fe-Si Alloy with Different Microchemistry States
Authors: Huang Ke , Li Yan Jun , Marthinsen Knut
Published: June 2014

In this paper, investigations of the softening behaviour of a supersaturated Al-Mn-Fe-Si alloy during annealing after cold rolling have been carried out. Two different homogenization conditions were considered, of which one gives a condition of a large amount of small pre-existing dispersoids, i.e. providing a significant static Zener drag, while the other gives a condition where both concurrent precipitation and dispersoid drag effects are limited. The homogenized samples with different microchemistry states were then cold-rolled to different strains before subsequent annealing at 300°C. The softening and concurrent precipitation behaviours have been monitored by hardness and electrical conductivity measurements respectively, and the microstructural evolution has been characterized by EBSD. It is clearly demonstrated that the actual microchemistry state, i.e. amount of solutes and second-phase particle structures as determined by the homogenization procedure strongly influence the softening behaviour where a fine dispersion of pre-existing dispersoids together with concurrent precipitation slow down the recrystallization kinetics considerably and give a very coarse and elongated grain structure.
Serration and Reversion Treatment in Al-Zn Alloys
Authors: Kanadani Teruto , Nagata Norihito , Nakagawa Keiyu , Hino Makoto , Murakami Koji
Published: June 2014

Aging phenomena of Al-Zn alloys have been much investigated and many studies have been made on the change of mechanical properties on aging. Appearance of saw-tooth yielding (serration) in the stress-strain curve of tensile deformation has been reported in several reports. In this study, the relationship between occurrence of serration and reversion heat treatment was studied by tensile test on Al-Zn alloys. Serration was observed for the furnace cooled specimen, but not for the as-quenched one and the shortly aged one, which result is difficult to be interpreted by the Cottrell theory. The stress amplitude in the serration increased with increasing the time of annealing for reversion and then stayed at a constant value which might be interpreted by the Cottrell theory. The stress amplitude in the serration decreased with increasing the annealing temperature, which is contrary to the prediction by the Cottrell theory. The specimen directly annealed without aging and the one annealed after aging agreed well with each other in the tensile strength and the stress amplitude in the serration, which suggests solute clusters as the cause of serration.
The Effect of Mn on Microstructure Evolution during Homogenization of Al-Mg-Si-Mn Alloys
Authors: Liu Cheng Lu , Azizi-Alizamini Hamid , Parson Nick C. , Poole Warren J.
Published: June 2014

A study was conducted on the evolution of microstructure during homogenization for two Al-Mg-Si alloys with different Mn levels, i.e. 0 and 0.5wt%. The homogenization treatment was conducted over a wide range of temperatures above the Mg2Si solvus. The holding time at the peak temperature ranged from 2 hour to one week. Microstructure evolution of the constituent particles and Mn dispersoids were characterized by means of optical microscopy and FEG-SEM. The Mn content in and out of solution was estimated using the Thermo-calc (TTAl6 database) and resistivity measurements. The micro-segregation and distribution of the main alloying elements before and after homogenization were systematically studied by electron probe micro analysis (EPMA). It was found that the Mn content together with the homogenization practice had a significant influence on the microstructure evolution. By combining all the measurements, a comprehensive quantitative dataset describing microstructure evolution during homogenization was developed.
Comparative Study of Microstructural and Corrosion Characteristics of Excimer Laser-Melted AA2124-T4 and AA6061-T4 Alloys
Authors: Qian Dai Shu , Liu Zhu
Published: June 2014

A KrF excimer laser was introduced for laser surface melting (LSM) of the aluminium alloys AA2124-T4 and AA6061-T4. The microstructural and compositional analysis was conducted using SEM, low-angle XRD, and TEM; the corrosion behaviour of as-received (AR) and laser-treated (LT) samples was evaluated by electrochemical techniques and immersion test in a 3.5% NaCl solution. A melted layer consisting of a re-solidified layer with refined microstructure and dissolution of intermetallic particles (IMPs), and a thin film of aluminium oxides at the top, was formed after LSM for both alloys. The corrosion resistance of both alloys was improved after LSM. The results of immersion test showed different corrosion behaviour for LT AA2124 and LT AA6061. The delamination of the melted layer was observed for AA2124 but was not observed for AA6061 after exposure to 3.5% NaCl solution for 24 h. This was attributed to the formation of copper-rich segregation bands in the melted layer of AA2124 due to higher content of copper in AA2124 than AA6061. A significant number of micro-pores were present in the melted layer for AA2124 treated with high number of laser pulses, leading to the decrease of the corrosion resistance.
Effect of Scandium Addition on Mechanical Properties and Corrosion Resistance of Medium Strength Al-Zn-Mg-Cu) Alloy
Authors: Ryabov Dmitry K. , Kolobnev Nikolay I. , Samohvalov Sergei V.
Published: June 2014

Al-Zn-Mg alloys are widely used construct material for wide range of application including automotive industry, building, and aviation. Scandium is rare earth metal, which modifies structure of semi-products and can lead to increasing of tensile and yield strength because of Al3Sc intermetallics of nanoscale size. This paper describes results of influence of small addition of scandium (0,08 wt. %) on mechanical and corrosion properties of cold-rolled sheets of 1913 alloy. 1913 is Russian medium strength corrosion resistant weldable Al-Zn-Mg alloy with addition of Cu for improvement of stress corrosion resistance and Mn with Zr for structure improvement. It is shown that addition of Sc transforms kinetics of artificial aging and accelerates decomposition of solid solution, besides tensile strength increases up to 50 MPa in artificially aged tempers. Changes in microstructure and quench sensitivity are described; results of intergranural corrosion, exfoliation and stress corrosion tests are introduced after different heat treatment including peak strength aging and overaging tempers.
Aging Process during Creep Deformation in an Al-Mg-Si Alloy Affected by Pre-Aging Condition
Authors: Ando Makoto , Suzuki Yoshikazu , Niikura Akio , Itoh Goroh
Published: June 2014

Creep behavior of an Al-0.3%Mg-0.5%Si alloy affected by pre-aging condition was investigated to obtain fundamental knowledge on the thermal stability in the service temperature range for the precipitation-hardened aluminum heat-exchanger. The alloy was aged at 175 °C for 3 h (under-aged) and 24 h (peak-aged), after solution treatment, and then subjected to creep testing at temperatures of 150 °C and 200 °C. When the creep temperature was 150 °C, the under-aged (UA) specimen showed a lower creep rate than that of the peak-aged (PA) specimen. On the other hand, when the creep temperature was 200°C, both specimens showed almost the same creep rate. In other words, the UA specimen had higher creep resistance than the PA specimen at 150 °C, whereas this advantage disappeared at 200 °C. The difference was thought to originate from the precipitation during creep testing.
Effect of Heat Treatment and Alloying Element on Impact Energy Absorption of AlSi10 Casting Alloys
Authors: Bozorgi Salar , Anders Kevin , Angermeier Christoph , Chimani Christian
Published: June 2014

The automotive applications using heat-treatable aluminum cast alloys are designed for high impact energy which can be improved using specified casting process and different heat treatment. In this study an economical and convent squeeze casting machine was used to produce the u-profile with 3mm wall thickness under controlled solidification conditions. The casted samples were used for mechanical and metallographical characterization. The mechanical properties of alloys containing different amount of Fe, Mn und Mg were determined as a function of different heat treatment condition such as modified T7 and Silicon Spheroidization Treatment (SST). The microstructure of casted alloys were quantificational determined by a combination of light optical microscope and scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS) module to identify the morphology and chemical composition of intermetallic eutectic phases. The results of Charpy impact test show that impact energy increases after modified T7 or SST heat treatment significantly compared with the as cast state. Furthermore the impact energy is less in the higher Mg containing alloys (0.15wt.%) compared with the less Mg containing alloy (0.07wt.%).
Influence of Processing Route on the Work-Hardening and Ductile Fracture of an AA6060 Aluminium Alloy
Authors: Hopperstad Odd Sture , Westermann Ida , Pedersen Ketill Olav , Furu Trond , Børvik Tore
Published: June 2014

Tensile tests on smooth and notched axisymmetric specimens were carried out to determine the large strain work-hardening curves and the ductile fracture characteristics of an AA6060 aluminium alloy for three different processing routes. The alloy was processed in three subsequent steps: 1) casting and homogenization, 2) extrusion, and 3) cold rolling and heat treatment to obtain a recrystallized grain structure. After each processing step, the material was tested after natural ageing for more than one week. A laser-based extensometer was used to continuously measure the average true strains to failure in the minimum cross-section of the specimens and the true stress-strain curves were calculated. Since these curves are influenced by necking, they do not represent the correct work-hardening of the material. Accordingly, finite element (FE) simulations of the tensile tests on the smooth axisymmetric specimens were conducted to determine the work-hardening curves to failure, using an optimization tool that interfaced with the nonlinear FE code and the experimental stress-strain curves as objectives. The microstructure of the alloy was characterized after the three processing steps by optical and scanning electron microscopy, and fractography was used to investigate the failure mechanisms.
Subgrain Structures Characterized by Electron Backscatter Diffraction (EBSD)
Authors: Bunkholt Sindre , Marthinsen Knut , Nes Erik
Published: June 2014

Subgrain structures are frequently characterized by the electron backscatter diffraction (EBSD) method, which is both accurate and provides good statistics. This is essential to better understand the subgrain growth mechanisms and e.g. establish the driving forces and motilities for comparison with physically based models. However, there is no commercially available software which can provide adequate subgrain boundary maps necessary for e.g. size and misorientation analysis. Here, a method that produces such maps utilizing only commercially available software is presented. The clue is to provide the EBSD-software with a parameter that can be used to identify all subgrains. By combining various maps exported from the EBSD-software into photo editing software, a new map is made in which all subgrain boundaries are identified. Missing and incomplete boundaries are traced manually before a reconstructed subgrain map is generated and imported back into the EBSD-software. With this method, the built-in algorithms in the EBSD-software can be readily used to e.g. characterize subgrain growth in aluminium with respect to orientation, size and misorientation.
Grain-Size Dependency of Low-Temperature Creep in Ultrafine-Grained Aluminum
Authors: Sato Eiichi , Komiyama Yuto , Sato Yoshimitsu
Published: June 2014

The grain size dependence of creep behavior from coarse grain to ultrafine grain regions was examined using fully-annealed specimens fabricated from a single process route. For coarse-grained sample, in tensile deformation, stress-strain curves show slow work hardening, and the proof stress shows typical Hall-Petch behavior. On the other hand, creep behavior is observed under the stress above the proof stress, and the creep rate has no grain size dependence. For ultrafine-grained sample, in the tensile deformation, stress-strain curves show yielding behavior, and the yield stress shows Hall-Petch behavior also. On the other hand, creep behavior was observed below the proof stress, but the creep rate decreases with a decrease in grain size.
A Positron Study of Early Clustering in Al-Mg-Si Alloys
Authors: Liu Meng , Čížek Jakub , Chang Cynthia S.T. , Banhart John
Published: June 2014

Early stages of clustering in quenched Al-Mg-Si alloys during natural ageing were studied by positron annihilation lifetime spectroscopy utilizing its unique sensitivity to electron density differences in various atomic defects. Two different positron trapping sites could be identified, one related to a vacancy-type defect, the other to solute clusters. The first trap is deep, i.e. irreversibly traps positrons, the second shallow, from which positrons can escape, which creates the signature of a temperature-dependent positron lifetime. During the first 80 min of NA, the vacancy-related contribution decreases, while the solute clusters increasingly trap positrons, thus reflecting their continuous growth and power to trap positrons. Coincident Doppler broadening spectroscopy of the annihilation radiation shows that the annihilation sites are Si-rich after quenching but contain more Mg after 70 min.
Solid State Joining of Aluminium to Titanium by High Power Ultrasonics
Authors: Balle Frank , Magin Jens
Published: June 2014

In this paper selected results about process control and stability during ultrasonic torsion welding of aluminium to titanium sheets are discussed. The process parameters welding force, welding energy and oscillation amplitude were optimized for Al4N/cp-Ti-joints and AA7075/TiAl6V4-joints using modern statistical test methods. The hybrid welds are evaluated and compared based on their mechanical properties. Furthermore thermal characteristics are determined with high resolution during the welding process by thermometry. Central aspects of the current research project are detailed microscopy of the hybrid interface as well as fracture surface analysis to understand the interfacial formation. Relationships between process parameters, joint strength and the related microstructure should be understood.
Effect of Coating Layer on Advanced Stud Welding of 2024 Aluminum Alloy to Galvanized and Galvannealed Steel Sheet
Authors: Harada Yohei , Ishizuka Kozo , Kumai Shinji
Published: June 2014

High strength 2024 aluminum alloy studs were joined to galvanized, galvannealed and non-coated steel sheets by using an advanced stud welding method. Effect of the coating layer on the interfacial microstructure and the tensile fracture load of the joints were evaluated. A specially-designed stud having a circular projection at its bottom was pressed against a sheet surface. A discharge current was introduced from the upper part of the stud. Local heating could be achieved by a high current density at a contact point between the projection and sheet. The observation of joint area revealed the projection was severely deformed and spread along the sheet surface. The coating layer of the galvanized steel sheet was removed at the joint interface under the charging voltage of 200 V, while that of the galvannealed one locally remained on the steel surface even at 400 V. This would be strongly related to the melting or liquidus and solidus temperatures of each coating layer. Joining was not achieved at a low charging voltage in the non-coated and galvannealed steel sheets, while high tensile fracture load was obtained even at 200 V in the galvanized ones.
Friction Stir Welding of an Al-Mg-Sc-Zr Alloy with Ultra-Fined Grained Structure
Authors: Malopheyev Sergey , Mironov Sergey , Kulitskiy Vladislav , Kaibyshev Rustam
Published: June 2014

Effect of friction stir welding (FSW) on mechanical properties and microstructure of Al-5.4Mg-0.2Sc-0.1Zr sheets with ultra-fined grained (UFG) structure was studied. The UFG-sheets were produced by equal-channel angular pressing (ECAP) followed either by cold or hot rolling. FSW was found to be very effective for retaining the UFG microstructure as well as constituent coherent nano-scale dispersoids in the welded material. Despite the preservation effect, however, the essential material softening was observed in the weld zone. This was attributed to the recrystallization occurring during FSW. The joint efficiency for yield strength of the obtained friction stir welds was found to be 81% in the hot rolled condition and only 55% in the cold rolled state. The relatively low joint efficiency was associated with the recrystallization softening as well as with the formation of a specific “kissing bond” defect in the stir zone. The joint efficiency is believed may be improved by adjusting of welding conditions and/or tool design.
Systematic Evaluation of the Advantages of Static Shoulder FSW for Joining Aluminium
Authors: Wu Hao , Chen Ying Chun , Strong David , Prangnell Phil B.
Published: June 2014

Static Shoulder Friction Stir Welding (SS-FSW) is a modification to conventional FSW that was originally developed to improve the weldability of titanium alloys by reducing through thickness temperature gradients. Surprisingly, to date, there have been no published systematic studies comparing SS-FSW to FSW for aluminium welding. This may be because the high conductivity of aluminium means the heat input produced by the shoulder is thought to be beneficial. In the work presented when welding a high strength 7050 aluminium alloy, even in a relatively thin 6 mm plate, it is shown that SS-FSW has several advantages; including a reduction in the heat input, a massive improvement in surface quality, and a more uniform through thickness temperature distribution, which leads to narrower welds with a reduced heat affected zone width and more homogeneous through thickness properties. The reasons for these benefits are discussed.
Characterization of AMAG AL6-CHA Sheet Material for Chassis Application in the Automotive Industry
Authors: Berneder Josef , Prillhofer Ramona , Enser Josef , Rank Gunther , Grohmann Torsten
Published: June 2014

Aluminium is already extensively used in car production to reduce the CO2 emissions by weight reduction. A further beneficial effect of lightweight design can be generated in components of the chassis by reducing the weight of unsprung mass thereby enhancing the driving comfort and reducing the noise level. The medium strength alloys of the type AlMg3Mn (EN AW-5754) and AlMg3.5Mn (EN AW-5454) are currently the aluminium sheet material choice for application in chassis components. The newly developed alloy AMAG AL6-CHA was optimized with regard to chassis applications and shows the potential of significant increase of the mechanical properties compared to state-of-the-art 5xxx series alloys. AMAG AL6-CHA, which is a 6xxx series alloy with balanced Mg/Si-ratio, is characterized with regard to mechanical properties and intergranular corrosion resistance in delivery temper T4 and after artificial aging with the typical heat treatment cycle 205 °C/60 min in peak aged temper T6. Furthermore we will show the results of the Charpy-V-notch impact test and the formability is described per bend test and grain size analysis.