bluuebunny/crossref_metadata_2025 huggingface dataset:
Copper Flow Simulation to Severe Plastic Deformation by Multiaxial Forging
Authors: Bejinariu Costică , Cazac Alin , Alexandru Adrian , Toma Stefan Lucian
Published: August 2015

Today, computer numerical simulations take place increasingly trials. The development of computers, increasing data storage capacity and computing speed, led to appearance of specialized software for virtual simulation of most plastics processing procedures. With these programs you can get answers to fundamental problems of plastic deformation: the size and stress distribution within the body, breaking predicting how the material flow, final shape of the product. Copper flow simulation is necessary for predetermination of total plastic deformation force, which is used to choose the machine deformation. Also, flow simulation aims to determine material contact tensions - deformation tools, necessary tension for sizing tool, in this case the active plate, punch and conterpunch.
Development of Fly Ash-Based Geopolymer Lightweight Bricks Using Foaming Agent - A Review
Authors: Wan Ibrahim Wan Mastura , Kamarudin Hussin , Al Bakri A.M. Mustafa , Kadir Aeslina Abdul , Binhussain Mohammed
Published: August 2015

Bricks are widely used as a construction and building material due to its properties. Recent years have seen a great development in new types of inorganic cementitious binders called ‘‘geopolymeric cement’’ around the world. This prompted its use in bricks, which improves the greenness of ordinary bricks. The development of fly ash-based geopolymer lightweight bricks is relatively new in the field of construction materials. This paper reviews the uses of fly ash as a raw materials and addition of foaming agent to the geopolymeric mixture to produce lightweight bricks. The effects on their physical and mechanical properties have been discussed. Most manufactured bricks with incorporation of foaming agent have shown positive effects by producing lightweight bricks, increased porosity and improved the thermal conductivities of fly ash-based geopolymer bricks. However, less of performances in number of cases in terms of mechanical properties were also demonstrated.
Preliminary Results on Microstructural, Chemical and Wear Analyze of New Cast Iron with Chromium Addition
Authors: Florea Costel , Bejinariu Costică , Carcea Ioan , Paleu Viorel , Chicet Daniela Lucia , Cimpoeşu Nicanor
Published: August 2015

A new cast-iron material was obtained by melting in an induction furnace. The material was microstructural and chemical characterized before and after a wear test. We analyze the chemical composition of the material at macro-scale using a Spark Spectrometer and at micro-scale using Dispersive Energy Spectrometer. Microstructure before and after the external solicitations was observed using a Scanning Electron Microscope. We also evaluate the influence of external force on the dendrites microstructural and chemical modification.
Conduction Properties of PTMSPMA-PEO and its Application as Polymer Electrolyte in LiFePO4 Batteries
Authors: Hidayat Sahrul , Amelia Orina , Rahayu Iman , Fitrilawati
Published: August 2015

The conduction properties of polymer composite PTMSPMA-PEO as electrolyte in lithium-ion batteries has been investigated. The gel polymer of PTMSPMA was synthesized by sol-gel method using 3-(Trimethoxysilyl)-propyl-methacrylate as monomer. The Composite of PTMSPMA-PEO with various composition (50:50, 60:40, 80:20; wt%) was made by solution method. The polymer electrolyte was composed of LiClO4salt dissolved in propylene carbonate and mixed with PTMSPMA-PEO. The ionic conduction of polymer electrolyte was characterized by electrochemical impedance spectroscopy. The battery performance of polymer electrolyte was estimated with coin cell, where LiFePO4was used as cathode and graphite was use as anode. The high ionic conductivity of 6.67 x10-3S/cm has been observed for the composition of PTMSPMA : PEO 60:40 (wt%) in room temperature. The performance of cell battery was investigated by charge-discharge using constant current 0,1 mA/cm2. The operational voltage of cell battery is around 1 V until 2.2 Volt with Columbic efficiency around 60%.
Study on Carbon-Coated LiMn0.7Fe0.3-xNixPO4 (0 ≤ x ≤ 0.15) as Cathode Material for Lithium Ion Batteries
Authors: Triwibowo Joko , Setiawan Jan , Purawiardi Raden Ibrahim , Prihandoko Bambang
Published: August 2015

Phosphate-based cathode material, LMP, with olivine crystal structure is generally known as cathode material with low electronic conductivity. Therefore, these materials should be coated by conductive materials. In this study the synthesis of carbon-coated cathode material and dopant variations in cathode material to improve the working potential of the battery are observed. The process of synthesis is carried out through the conventional solid-state process. The starting materials, Li2CO3, MnO2, Fe, Ni and NH4H2PO4 in the powder form are mixed homogenously. The homogeneous mixture is further mixed with a solution of in water dissolved citric acid. This is then dried in oven for 24 hours. The dry mixture is then heated at a temperature of 320°C for 10 hours in a furnace with an inert atmosphere. The obtained powder is subsequently heated at 800°C for 8 hours in the furnace with flowing nitrogen gas. Phase of the powder obtained after the second heating was analyzed by XRD. Phase compositions were analyzed by Rietveld refinement method through a GSAS-software. Analysis of the microstructure and morphology are performed by SEM and BET. Cathode material performance is analyzed by using the Charge-Discharge battery analyzer. To perform Charge-Discharge analysis, cathode material is assembled into a half cell with metallic lithium as the counter electrode and 1 M LiPF6 dissolved in EC: DEC (1: 1 v / v) as the electrolyte.
Study of Charge Carrier Dynamics of P3HT:PCBM Blend for Active Material Solar Cell Using Muon Spin Relaxation
Authors: Bahtiar A. , Safriani Lusi , Aprilia Annisa , Risdiana  , Harsojo  , Triwikantoro  , Darminto  , Nugroho Agustinus Agung , Guo Hanjie , Kawasaki Ikuto , Watanabe Isao
Published: August 2015

Poly (3-hexylthiohene) (P3HT) has attracted much attention due to their chemical and thermal stability as well as their potential to be used as an active material in solar cells. Recently, bulk-heterojunction BHJ solar cell has been intensively developed due to its potential for high power conversion efficiency and low cost solar cells. Many studies have been done to understand the effect of PCBM to the morphology of the P3HT:PCBM blend and to performance of its solar cells. However, the clearly explanation about the effect of PCBM to the charge carrier dynamics in P3HT is not well understood yet. We have studied charge carrier dynamics in active material of solar cell P3HT:PCBM along and perpendicular to the chain by means of longitudinal field (LF) muon-spin-relaxation (μSR) method to elucidate the intra and inter-chain charge carrier in polymer hybrid P3HT:PCBM. We found the charge carrier transport changes from intra-chain to inter-chain diffusion. One dimensional intra-chain diffusion is observed in the samples at low temperatures below 10K, while three dimensional inter-chain is observed at high temperatures above 15K. This temperature is lower than that of P3HT only.
Synthesis of Cobalt Ferrite Particles by Utilized Sol-Gel Method
Authors: Saragi Togar , Nurjannah Siti , Novia Ricca , Syakir Norman , Simanjuntak Edward , Safriani Lusi , Risdiana  , Bahtiar Ayi
Published: August 2015

Cobalt ferrite (CoFe2O4) nanoparticles were successfully synthesized by utilized sol gel method with controlled pH and temperature solution during reflux process in order to obtain monodispersed nanoparticles with high magnetic properties. The obtained cobalt ferrite particles are oval with the size vary from 100 nm to 220 nm. The Co˗O and Fe˗O bonds are formed as confirmed by FTIR measurement. The sample has high quality crystal with spinel structure as indicated by similar XRD pattern of the sample and the JCPDS (00-001-1121) data without impurity peaks. From the Vibrating Sample Magnetometer (VSM) measurement, magnetic remnant around 0.2303 emu/cc and coercive field around 2.7039 kOe are obtained.
The Orientation Study of Ba-Sr Hexaferrite Particles by Parallel Magnetic Field Press
Authors: Wismogroho Agus Sukarto , Widayatno Wahyu Bambang , Sudiro Toto , Aryanto Didik
Published: August 2015

It is well known that an orientation treatment on magnetic particles may increase magnetic flux density than that of those without treatment. In this work, the study on orientation of Barium Stronsium Hexaferrite (Ba-Sr Hexaferrite) particles using parallel system of magnetic field press was conducted to investigate the effect of powder orientation on its characteristic. Samples were compacted while the varied magnetic field induction were given, molded and then sintered at 1200°C for 1 hour. The measurement of magnetic properties showed that orientation process increased the value of magnetic remanence up to 173% (1264 Gauss). The magnetic field induction of 0.4 T was found to be the optimum value, where further increase of magnetic field did not give significant change. The crystal structure analysis showed the increase of peak of <001> plane which is correlated with the c-axis of Ba-Sr Hexaferrite crystal. In addition, the peak which is correlated with the opposite direction of c-axis disappeared, while the peaks between those directions decreased significantly. The micrograph of Ba-Sr Hexaferrite particles showed the alignment of c-axis parallel to the given magnetic field induction. These results showed the phenomenon of mechanical particle revolving and particle arrangement during the orientation process by which determined the obtained magnetic remanence.
Various Magnetic Properties of Magnetite Nanoparticles Synthesized from Iron-Sands by Coprecipitation Method at Room Temperature
Authors: Sunaryono  , Taufiq Ahmad , Mashuri  , Pratapa Suminar , Zainuri M. , Triwikantoro  , Darminto
Published: August 2015

Natural sand-based magnetite nanoparticles have been succesfully synthesized by coprecipitation method at room temperature. Magnetite nanoparticles were investigated by X-ray Diffractometer (XRD) and Vibrating Sample Magnetometer (VSM). The morphology of magnetite nanoparticles has been evaluated by Transmission Electron Microscopy (TEM). Qualitative analysis of XRD data reveals that the structure of magnetite nanoparticles have the same phase of ICSD No. 82237. On the other hand, quantitative analysis shows that the crystallite size of magnetite nanoparticles have ranges between 8.89 nm to 12.49 nm. The average diameter of magnetite nanoparticles increase with the increase the stirring rate of reaction when the stirring rate is lower than 1000 rpm, while the crystallite size of magnetite particles decrease with the increase the stirring rate when the stirring rate is higher than 1000 rpm. The stirring rate of reaction influence the the magnetic properties of magnetite nanoparticles. The results of the best magnetic respon are revealed for the stirring rate of 1000 rpm with the larger the crystallite size of magnetite nanoparticles due to its stronger saturation magnetization.
Comparative Study of Photocatalytic Activity of Ni-Doped ZnO and Zeolite Supported Ni-Doped ZnO Prepared by Co-Precipitation Method
Authors: Philipus Raynaldi , Noorhidayati Annisa , Djaja Nadia Febiana , Saleh Rosari
Published: August 2015

The present study compares the photocatalytic degradation of methylene blue in the presence of natural zeolite supported Ni-doped ZnO and bare Ni-doped ZnO nanoparticles. The photocatalyst was prepared by co-precipitation method and the photocatalytic activity of the photocatalyst was investigated under UV light irradiation. The results showed that the photocatalytic efficiency of zeolite supported Ni-doped ZnO nanoparticles is better than that of bare Ni-doped ZnO nanoparticles. The influence of experimental parameters on the photodegradation of methylene blue was studied and it was observed that photocatalytic activity varied with pH, initial methylene blue concentration and the amount of photocatalyst. The scavenger technique shows that electron plays an important role in the bare Ni-doped ZnO, while in zeolite supported Ni-doped ZnO,●OH is the prominent active species.
Functionality of ZnPc Thin Film Deposited on Polystyrene Interlayer for Immobilization of Biomolecules in QCM Based Biosensor
Authors: Santjojo D.J. Djoko H. , Masruroh  , Widyarti Sri , Robiandi Fadli
Published: August 2015

Functionality of zinc pthalocyanine (ZnPc) thin film for immobilization of biomolecules was studied using bovine serum albumin (BSA). The functionality is affected by microstructures and surface roughness of the film. This studies is conducted by producing ZnPc films by means of thermal evaporation in vacuum. The ZnPc films were deposited on quartz crystal substrates with a polystyrene interlayer. Observations were carried out using a scanning electron microscope and an optical micro-profilometry. Enhancement of the functionality is observed with the increase of the film thickness. Surface roughness and microstructures of the film influence the functionality in a complex way. Adsorbtion of the BSA molecules is associated with both the surface roughness and microstructures. Although generally the adsorption is proportional to the contact area but the roughness and fibrous microstructures of the deposited ZnPc produce complex adsorption and trapping mechanisms in the immobilization of the BSA.
Fabrication of Photonic Crystal Based on Polystyrene Particles
Authors: Safriani Lusi , Sopian Ian , Susilawati Tuti , Hidayat Sahrul
Published: August 2015

Photonic crystals are dielectric materials with different refractive index or permittivity periodically. Photonic crystals have widely application for future technology such as waveguide, optical transistor, cavity of laser and biosensor. Photonic crystals can be fabricated in three types i.e 1D, 2D and 3D structure. In this paper, we report the successful fabrication of 3D photonic crystal from polystyrene particles. The fabrication process began with the synthesis of polystyrene particles followed by deposition on glass and flexible substrate using self-assembly method. We obtained polystyrene monodispered particles which have a uniform shaped with diameter 320 nm. Self-assembly method resulted to the arrangement of polystyrene particles on glass and flexible substrate. Stop band which is related to its optical property are at wavelength of 721 nm and 631 nm for photonic crystal on glass and flexible substrate, respectively. We found that filling fraction of photonic crystal on flexible substrate is lower than that of glass substrate due to some defects.
Synthesis of Styrofoam Fibers Using Rotary Forcespinning Technique
Authors: Fauzi Ahmad , Edikresnha Dhewa , Munir Muhammad Miftahul , Khairurrijal
Published: August 2015

Development of rotary forcespinning (RF) to synthesize fibers has been done. High speed motor driven centrifugal force becomes a major factor in the formation of fibers. RF apparatus consists of three main parts namely the motor system, the collector, and the heating system that serves to regulate the temperature and humidity around the motor. The liquid polymer was poured in the motor holder and rotated at high speed so that the liquid was dropped from the tip of the needle to the collector in the form of fibers. In this study, the liquid polymer was from waste polystyrene foam (styrofoam) soaked in acetone at a certain ratio. The observation was done with the digital microscope up to 1000 times of magnification. The produced styrofoam fibers were similar to homogeneous and smooth cotton with an average fiber diameter in micrometer. The utilization of waste styrofoam into the fibers is expected to reduce the environmental problems caused by waste styrofoam.
Electrospun Nanofibers Based on Polyvinyl Alcohol/Chitosan and its Stability in KOH Solution
Authors: Triyana Kuwat , Mu’min M. Solihul , Faizah Kuni , Yusuf Yusril , Kusumaatmaja Ahmad , Harsojo
Published: August 2015

Fabrication of nanofibers based on polyvinyl alcohol and chitosan (PVA/chitosan) has been carried out by means of electrospinning with focusing on beads formation and diameter variation due to effects of weight ratio variations of PVA/chitosan. For electrospinning solution, the PVA/chitosan with artios of 10:1, 10:2 and 10:3 w/w were dissolved in 1% acetic acid. In addition, stability testing of PVA/chitosan nanofibers in an electrolyte solution was performed by soaking the nanofiber mat in KOH solution. As results, the addition of chitosan concentration increased the pH, conductivity, and viscosity of the solution. Beads were potentially generated for low chitosan concentration. Furthermore, the effect of viscosity and conductivity on diameter of electrospun nanofibers is very significant and need to be optimized. The average diameter of electrospun nanofibers were found to be 160 ± 18 nm, 120 ± 12 nm, and 148 ± 26 nm, for weight ratios of PVA and chitosan 10:1, 10:2 and 10:3, respectively. In addition, no significant change in morphology after being soaked the electrospun PVA/chitosan nanofibers in KOH 40 wt% solution for 24 hours. It indicates that the electrospun PVA/chitosan nanofibers is stable in electrolyte solution which shows a high potential for electrolyte membrane in fuel cells application.
Study of Alkalization to the Crystallinity and the Thermal Behavior of Arenga Pinnata “Ijuk” Fibers-Based Polylactic Acid (PLA) Biocomposite
Authors: Chalid Muchamad , Yuanita Evana , Pratama Juniko
Published: August 2015

The pollution due to non-degradable material such as plastics, has led to studies about the development of environmental-friendly materials. Because of natural sources-based materials and their biodegradability, polylactid acid (PLA) and ijuk fiber are interesting to be modified into a composite. Furthermore this study is also expected to reduce the impact of environmental problems. Surface modification of ijuk fiber through alkalinization, was aimed to enhance compatibility between the ijuk fiber and the PLA, in order to improve properties of the composite such as crytallinity and thermal behavior. To investigate in detail about this modification, this research also studied effect of the alkalinized ijuk fiber and the PLA composition to the crystallinity and the thermal behavior of the composites. The experimental results were investigated by FTIR to qualitatively analyze compounds content in the ijuk fiber before and after alkalinization, DSC and TGA to study crystallinity and thermal stability behavior of the composite, respectively and FE-SEM to observe morphological behavior like compatibility between the ijuk fiber and the PLA. The FE-SEM observation showed that alkalinization of the ijuk fiber led to wettability enhancement between the ijuk fiber and the PLA. This may be caused by annihilating lignin and hemicellulose. Furthermore this treatment leads to expose micro-fibril cellulose (MFC) in the ijuk fiber and then to enhancement of bonding affinity with the PLA. This phenomenon gives a possibility for the PLA in the composite to increase its crystallinity due to nucleating effect of crystalline parts in the MFC. DSC measurements show that addition of the alkalinized ijuk fiber tends to increase the crystallinity of PLA in the composites.Keywords: alkalization, Arenga Pinnata, compatibility, crystallinity, PLA, thermal stability
Muon Site Estimations by DFT Calculations in Metal and Insulating Systems
Authors: Watanabe Isao , Suprayoga E. , Adam N. , Mohm-Tajudin S.S. , Rozlan A.F. , Puspita D. , Asih R. , Astuti F. , Umar M.D. , Angel J. , Sulaiman S. , Mohamed-Ibrahim M.I.
Published: August 2015

A way to estimate muon sites in materials is reported. Since the muon has a positive charge, one easiest and conventional way to estimate muon positions is to calculate minimum potential positions. We applied our developed method to estimate those potential minimum positions to some systems which have been studied by mons at the RIKEN-RAL Muon Facility and showed well defined muon-spin precession behavior in magnetically ordered states. Tentative calculation results by using the density functional theory are reported.
UV-Light Absorption and Photocatalytic Properties of Zn-Doped CeO2 Nanopowders Prepared by Ultrasound Irradiation
Authors: Efendi Aula Fitra , Nurhasanah Iis
Published: August 2015

Ceria (CeO2) nanopowders doped with various Zinc (Zn) compositions were synthesized from solution by irradiating ultrasound waves. Ultrasound waves were irradiated to aqueous/isopropanol solution of cerium nitrate and zinc nitrate mixtures. Aqueous solution of ammonium hydroxide was droped into that solution until pH becomes 10. Dried precipitates were calcinated at 100°C to form CeO2 nanopowders. X-ray Diffraction (XRD) analysis shows the CeO2 nanopowder possess fluorite cubic structure. Ultrasound irradiation resulted in nanometric powder of CeO2 with spherical in shape. The addition of Zn into CeO2 reduces the particle size and shows strong absorbance in the ultra–violet (UV) region. Moreover, the addition of 20 mol% Zn is inhibiting photocatalytic activity of CeO2 under sunlight irradiation. These results suggest that Zn-doped CeO2 is more promising for UV radiation protection with no presence photocatalytic activity.
Photocatalytic Activities of Electrospun TiO2/Styrofoam Composite Nanofiber Membrane in Degradation of Waste Water
Authors: Rajak Abdul , Munir Muhammad Miftahul , Mikrajuddin Abdullah , Khairurrijal
Published: August 2015

TiO2/Styrofoam composite fiber membranes were synthesized by using an electrospinning system for water purification applications. Composite fiber membrane was fabricated from precursor solution prepared by dissolving Styrofoam in the mixture of tetrahydrofuran (THF), citronella oil and cajuput oil. The precursor solutions is mixed with TiO2powder with three variations based on the concentration (1:15,1:20 and 1:40). Textile dye with 50 ppm of concentration was performed as a model of waste water. The structure and morphology of each membrane were characterized by using scanning electron microscopy (SEM). The photocatalytic activity was investigated under the bulb light with 60 watt of power in the box of photocatalytic test. Observation of photocatalytic process were performed for 30 hours. The quantitative data of the decrease in the concentration of wantex solution were measured by using UV-Vis spectrometer and simple spectrometer which was developed recently. It was shown that there are significant decrease of the concentration of wantex solutions performed by each membrane. As many as 69% of wantex solution have been successfully degraded for 30 hours under the bulb light.
Characterization of Optical and Structure Properties of Polydimethylsiloxanes
Authors: Nusa Hanif Sulistiya , Astuti Widi , Kartasasmita Arief Sjamsulaksan , Virgana Rova , Syakir Norman , Bahtiar Ayi , Safriani Lusi , Risdiana
Published: August 2015

Polydimethylsiloxanes (PDMS), (CH3)3SiO-[Si(CH3)2O]n-Si(CH3)3, known as silicone oil is a tamponade liquid which is very important in vitreoretinal surgery, especially in the treatment of complicated retinal detachment. Here, we investigated the optical properties and structure of silicone oil with high viscosity silicone oil of 5500 cSt and low viscosity silicone oil of 1300 cSt in order to understand the changing of physical properties of silicone oil before and after using in vitreoretinal surgery as a tamponade liquid and analyze the relationship between the tamponade duration and changed in silicone oil properties. From UV-Vis spectroscopy and refractometer measurement, it is found some changes in transmittance and refractive index values in both silicone oil after using as a tamponade liquid. From fourier transform infrared (FT-IR) spectroscopy, some additional of functional groups of N-H and O-H bond are observed at 1634.5 cm-1 and 3435.7 – 3764.5 cm-1, respectively. The changes of optical and structure properties of silicone oil after using as a tamponade liquid are assumed to be responsible in emulsification of silicone oil and affect the transmittance quality at visible light spectrum. However, in this study, there is no linear corelation between tamponade duration and changed in silicone oil properties.
Solidification and Interface Reaction of Titanium Alloys in the BaZrO3 Shell-Mould
Authors: Li Chong He , He Jin , Wei Chao , Wang Hong Bin , Lu Xiong Gang
Published: August 2015

The investment casting technology is one of the major methods to produce the parts of the titanium due to its low production cost. However, the high activity of titanium melt gives rise to the requirement of high chemical stability of shell materials, to avoid or decrease the interfacial reaction between the mould and the melt. In this paper, a novel BaZrO3 – coated Al2O3 shell was first introduced to the investment casting of titanium alloy. The grain size and baking temperature on the properties of the novel mould were investigated, and then the Ti6Al4V and TiNi alloys were successfully casted by means of this shell. The alloy-mould interaction was discussed. The results showed that the mould achieve high mechanical properties when the content of coarse powder was 50% after sintering 4 hours under 1500°C, and the BaZrO3 coating exhibited an effective barrier to avoid the direct contact between the mould base material and the melt, the thickness of reaction layer of TiNi alloy was about 8 μm, and 17 μm to Ti6Al4V alloy, no refractory particles and elemental diffusion were observed inside the metal. This may imply that BaZrO3 is a promising candidate material for the investment casting of titanium alloy.
Determination of Optimum Process for Thermal Debinding and Sintering Using Taguchi Method
Authors: Seerane Mandy , Chikwanda Hilda , Machaka Ronald
Published: August 2015

Debinding involves long and delicate processing periods of removing binder components from a green body after injection moulding; failure to completely remove the binder components results in distortion, cracking, blisters and contamination at elevated temperatures. This study focuses on optimising thermal debinding process parameters on the basis of obtaining a defect-free part after sintering and also determining a sintering time that gives high sintering density. Thermal debinding was conducted after solvent debinding. The feedstock used to produce green compacts composed of Ti6Al4V powder and a wax-based binder. The binder’s backbone component is a low density polyethylene (LDPE). Careful selection of thermal debinding parameters was guided by thermo-gravimetric analysis (TGA) results. The Taguchi method was used to determine an optimum debinding process. Thermally debound compacts were analysed for residual binder using a TGA. Archimedes’ principle and optical microscopy were done to analyse the sintering density and microstructure of the sintered product, respectively. Optimum debinding and sintering conditions were identified. The study demonstrated that heating rate during debinding was the most influential factor that contributes to minimum residual binder followed by debinding dwell time and temperature. Longer sintering time of 4 h favoured higher density of 91.6 ±1.55%. A typical radial shrinkage level of 11.1 ±0.0816% was determined.
Powder Metallurgical Synthesis of Biodegradable Mg-Hydroxyapatite Composites for Biomedical Applications
Authors: Stüpp César Augusto , Mendis Chamini Lakshi , Mohedano Marta , Szakács Gábor , Gensch Felix , Müller Sören , Feyerabend Frank , Hotza Dachamir , Fredel Márcio C. , Hort Norbert
Published: August 2015

Biodegradable Mg alloys are a new class of temporary implant materials for musculo-skeletal surgery. Recent studies show that Mg-based alloys can be biocompatible and there is a high demand to design Mg alloys with adjustable corrosion rates and suitable mechanical properties. An approach to solving this challenge might be the use of Mg metal matrix composites (Mg-MMC). In this study, a Mg-MMC composed of ZK60 was investigated as the base material and hydroxyapatite (HA) particles were added for tailoring its properties. The composite was produced by high-energy ball milling followed by hot extrusion. This processing route was chosen, as HA in contact with molten Mg releases a toxic gas (phosphine – PH3). The HA particles were homogeneously distributed in the ZK60 matrix after ball milling and the composite was consolidated by hot extrusion. This work presents the influence of different amounts of HA on corrosion behavior and mechanical properties of the composite. Corrosion properties were evaluated by immersion and electrochemical measurements in physiological media at 37 °C. A slight improvement in the corrosion resistance was observed for Mg-MMC due to the presence of more stable corrosion products. Compression tests were used to measure the mechanical properties. Under compression, samples showed a slight increase in the compressive yield strength with the addition of HA, while the ultimate strength did not change significantly.
Development of a Continuous Cooling Transformation Diagram for an Al-Zn-Mg Alloy Using Dilatometry
Authors: Kumar Manoj , Ross Nigel , Baumgartner Iris
Published: August 2015

To develop CCT diagram using DSC requires the use of multiple devices in order to measure across the range of cooling rates required to develop the diagram. In the current work one dilatometer is used to characterize the precipitation reactions of the AA7020 alloy. Precipitation and dissolution reactions resulted in changes in the rate of change in the coefficient of thermal expansion. This was used to determine the start and finish temperatures of the MgZn2 precipitation reaction and produce the CCT diagram. Good agreement was found between the results of this technique and DSC results from the literature.
Influence of Ageing Heat Treatment on Microstructure and Mechanical Properties of a Secondary Rheocast AlSi9Cu3(Fe) Alloy
Authors: Capuzzi Stefano , Timelli Giulio , Fabrizi Alberto , Bonollo Franco
Published: August 2015

The effects of different process parameters (temperature and time) during the ageing treatment on the microstructure and the mechanical properties of a secondary rheocast AlSi9Cu3(Fe) alloy have been examined. Optical microscope investigations have been performed to qualitatively study the microstructure of the as-rheocast and thermal treated alloys. Transmission electron microscopy technique and selected area electron diffraction analyses have been used to characterize the hardening phases precipitated in the Al-matrix during the different ageing stages. The evolution of mechanical properties of the Al matrix has been monitored by micro-hardness testing.
Bending Collapse Behaviour of Polyurethane Foam-Filled Rectangular Magnesium Alloy AZ31B Tubes
Authors: Zhou Ping , Beeh Elmar , Friedrich Horst E. , Kriescher Michael , Straßburger Philipp , Holzapfel Martin , Kraft Harald , Rieger Cedric , Oswald Katja , Roettger Jan
Published: August 2015

Quasi-static/dynamic three-point bending tests were conducted to assess the crash performance of magnesium alloy AZ31B extruded and sheet tubes at the German Aerospace Centre (DLR) – Institute of Vehicle Concepts in Stuttgart. Different foam-filled AZ31B beams with a variation of foam density and thickness were fabricated through several manufacturing processes: cold bending, tungsten inert gas welding, cathodic dip painting and polyurethane foam injection. The experimental results were compared with those from mild steel DC04 tubes. It shows that empty magnesium alloy AZ31B outperforms steel DC04 in terms of specific energy absorption for the empty tubes with equivalent volume when subjected to bending loads. It was found that the foam-filled tubes achieved much higher load carrying capacity and specific energy absorption than the empty tubes. Moreover, there is a tendency showing that a foam-filled beam with a higher foam density reaches higher load carrying capacity, but fractures earlier. The foam-filled AZ31B tube with 0.20 g/cm3foam obtained the highest specific energy absorption, but this outperformance was weakened due to the earlier fracture. In addition, the numerical simulation utilising material model MAT_124 in LS-DYNA explicit FEA package was performed. The simulation results indicate that using calibrated stress-strain curves and failure parameters, material model MAT_124 yields a general good agreement with the experimental results.
MagForge – Mechanical Behaviour of Forged AZ31B Extruded Magnesium in Monotonic Compression
Authors: Gryguc Andrew , Jahed Hamid , Williams Bruce , McKinley Jonathan
Published: August 2015

Monotonic compression testing was conducted on AZ31B-F magnesium alloy in both the as-received and forged conditions. Sigmoidal stress strain behaviour was the key feature in the majority of material conditions and directions corresponding to plastic behaviour where twinning de-twinning is the dominant deformation mechanism. More conventional monotonic hardening (slip deformation mechanism) was exhibited in certain material directions which initially were orthogonal to the extrusion direction in the as-received condition, but once forged are coincident with the direction of forging once forged. It was shown that in the forged condition, there is potential for significant increases in both ultimate tensile strength as well as strain to failure.
Mechanical Properties of Fibre Laser Welded AZ31B Sheets and their Dependence on the Spot-Size
Authors: Riekehr Stefan , Ravasi Riccardo , Enz Josephin , Ventzke Volker , Kashaev Nikolai
Published: August 2015

In the present work the mechanical behaviour of laser beam welded AZ31B alloy was studied, by changing systematically the spot size of the used fibre laser system between 200 µm and 1000 µm at different power levels between 2 kW and 8 kW. Maximum welding velocities with respect to imperfections were determined. The characterization of the obtained welds - in terms of Vickers hardness, UTS, Af and weld width, resp. weld area - was correlated with the micro-texture in dependence of the different Focus Spot Diameters and Laser Beam Power levels as well as the resulting cooling rates. Highest UTS of 94% of the base material was achieved with 200 µm Focus Spot Diameter and Laser Beam Power of 4 kW at welding velocity of 100 mm/s. By increasing the Focus Spot Diameter to 600 µm, the tensile strength was reduced to 86 % of the actual strength of the base material.
Residual Stress in SLM Ti6Al4V Alloy Specimens
Authors: Yadroitsava Ina , Grewar Stephen , Hattingh Daniel , Yadroitsev Igor
Published: August 2015

Selective Laser Melting (SLM) presents a modern manufacturing process with an innovative technology which allows the production of full-density objects or fine-structured parts with complex geometry and inner structures. Stability and certification of the properties of SLM parts are important tasks for all producers and end-users. One of the drawbacks of this technology is high residual stress in as-made SLM objects. In this study X-ray diffraction technique was used for investigating the residual stress induced into SLM Ti6Al4V alloy samples. Principal stresses were estimated for the cut rectangular specimen. Two types of the cantilevers were produced and numerical simulation of the stress was performed. The bending of cut cantilevers was measured before and after heat treatment. Next series of the samples had rectangular shapes and different thicknesses from 1 to 46 layers. All as-manufactured specimens attached to the substrate showed the presence of tensile residual stresses near the top surface. Residual stress along the laser scanning direction had magnitudes twice that of the stress in the perpendicular direction. Conclusions regarding directions and values of stresses in SLM objects from Ti6Al4V powder are given.
Pre-Treatment and Organic Coating of Al Free Mg Alloy for Controlling Degradation Rates
Authors: Scharnagl Nico , Mueller Phillip
Published: August 2015

Biodegradable implant material for medical applications has to fulfill specific therapeutic tasks. For our investigations, synthetic polymers, polyurethanes (PUR) and polyetherimide (PEI), were used. Both systems have been used to coat an Al-free Mg alloy. Characterization of materials was performed by IR, spark spectral analysis, microscopy and EIS. Electrochemical investigations of the different treated samples in aqueous NaCl and Hank's Balanced Salt Solution indicate specific response of the polymer/substrate system to corrosion attack.
Surface Microstructure Modification by Wire-Brushing and Annealing and its Effect on Tensile Ductility and Bendability of Mg Sheet
Authors: Habibnejad-Korayem Mahdi , Jain Mukesh K. , Mishr Raja K.
Published: August 2015

A wire brushing and annealing process is developed and utilized to modify the surface layer microstructure of AZ31 magnesium sheet material and assess its effect on uniaxial tensile ductility and bendability. Wire brushing process utilizing fine brass wires is optimized to minimize deterioration in original surface quality by varying spindle rotational speed and depth of cut per wire brushing pass. Wire brushed material is then subjected to annealing to recrystallize the severely deformed surface layer. Rotational speed of 2800 RPM, feed rate of 1 mm/s, and a very small depth of cut coupled with annealing at 200 °C for 60 minutes results in a refined grain layer of grain size 5.5 μm and depth 30 μm on the surface. A texture study of wire brushed and annealed surface by X-ray diffraction reveals a randomized texture on the surface. Refined grain size and randomized texture result in about 38% enhancement in uniaxial tensile elongation in AZ31 compared to non-wire brushed annealed material. The role of surface microstructure and texture in improving sheet tensile ductility and bendability is discussed.
Development of High Welding Speed in Friction Stir Welded 5182-H111, and the Resulting Influence on down Force
Authors: Bernard Dreyer , Hattingh D.G.
Published: August 2015

In this manuscript the development of the process parameters to friction stir weld 5.15mm thick AA5182-H111 at a feed rate of 1500mm/min is discussed. Compared to a weld made at 200mm/min the weld-pitch had to be reduced from 2.0rev/mm to 0.3rev/mm and down force increased from 27kN to 59kN to create a weld with tensile-and yield strength exceeding that of the parent material, whilst elongation was only marginally reduced. The low weld pitch coupled with the high feed rate resulted in a reduction in the weld temperature and an increase in the process reaction forces. A lower down force was sufficient to consolidate the stir zone and result in ultimate tensile strength yield strength exceeding that of the parent material. However, elongation was reduced since the low weld pitch also reduced the effectiveness of the flutes on the pin to break up and disperse the oxide layer, rendering a pseudo bond along the ‘Lazy S’. This pseudo bond was eliminated through an increase in the down force.
Fine Metallic Particle Emission when Milling Aluminium Alloys and Aluminium Metal Matrix Composites
Authors: Songmene Victor , Njoya Doko R.
Published: August 2015

Machining activities generate aerosols that can be harmful, degrade the environment or slow down theproduction. The main objective of this study was to evaluate the effects of machining conditions (cutting parameters and workpieces materials) on metallic particle emission during milling to help determining the machining conditions leading to ecological and occupational safe machining practices. The workpieces materials tested were aluminium alloys (6061-T0, T4 and T6 and A319) and aluminiummetal matrix composites (MMC) containing hard particles (SiC) for wear resistance and nickel-coated graphite particles for improved friction and machinability. It is found that the reinforcement within the aluminium MMCs reduces the fine particle emission as compared to unreinforced aluminium alloys. In general, the quantity of the particle emitted depends on the machining parameters settings. Among the aluminium alloys, the particle emission appeared to be dependent on material’s ductility.
Investigation of Primary Fe-Bearing Compounds in Secondary Aluminium Alloys by Differential Scanning Calorimetry
Authors: Timelli Giulio , Capuzzi Stefano , Fabrizi Alberto , Caliari Daniele
Published: August 2015

The precipitation of primary Fe-rich intermetallics (sludge) in AlSi9Cu3(Fe) type alloys has been investigated for different Fe, Mn and Cr contents and cooling rates. Differential scanning calorimetry was used in order to assess the nucleation temperature and the enthalpy of sludge particles as well as to follow their evolution. The results show that the sludge nucleation temperature and the release of latent heat during sludge formation are functions of the initial concentrations of Fe, Mn and Cr in the molten alloy, i.e. the sludge factor, and the cooling rate. Being able to predict the temperature of sludge formation will support the foundries to set the right molten metal temperature in order to prevent sludge precipitation during the entire high-pressure die-casting process.
A Comparative Study on the Sintering and Casting of a Blended Elemental Ti-6Al-4V Alloy
Authors: Masikane Muziwenhlanhla A. , Chikwanda Hilda K. , Sigalas Iakovos
Published: August 2015

Over the past years, the blended elemental powder metallurgy (PM) approach has been identified as one of the most promising strategies to reduce the cost of titanium-based components. However, oxygen pick-up, inhomogeneity of the microstructure and chemical composition are sometimes reported for PM parts. This work compares properties of a blended elemental Ti-6Al-4V alloy obtained by sintering under argon gas atmosphere with those of a vacuum cast alloy. Argon was purified by passing it through a series of oxygen and moisture traps prior to being introduced into the sintering furnace. Casting was performed under vacuum (1 x 10-3mbar). The starting material in both processes was the cold isostaticaly pressed blended elemental (BE) Ti-6Al-4V powder compact. The BE powder was prepared by mixing 60Al-40V master alloy powder with commercial Grade 4 titanium powder (0.377 wt.% O2). The sintered and cast alloys were compared on the basis of oxygen pick-up, density, microstructure, chemical composition and hardness to determine which method is better. Although the BE approach could not eliminate the common challenges associated with powder metallurgy processing of Ti alloys, oxygen pick-up and additional contamination was lower compared vacuum casting. Sintering at 1350°C for 1 h could not achieve full density compared to casting, but the microstructure appeared more homogeneous. Both sintered and cast Ti6Al4V alloys were harder than wrought Ti6Al4V due to a high concentration of interstitial oxygen. The sinterered and sintered plus HIPed Ti6Al4V alloys were softer than as-cast Ti6Al4V due to lower oxygen pick-up and incomplete densification. From the contamination and homogeneity perspective, the BE approach is an attractive technique for processing of Ti6Al4V alloy.
Determining a Flow Stress Model for High Temperature Deformation of Ti-6Al-4V
Authors: Calvert E. , Pollard J. , Jackson M. , Wynne B. , Thackray Richard
Published: August 2015

In some commercial titanium extrusion practices, twisting of the extrudate can occur, which can result in the need to crop the back and front end of the extruded material, thereby reducing yield and increasing material losses. Understanding more about the behaviour of material during the extrusion process, and investigating the cause of defects such as twisting by use of finite element (FE) modelling techniques could help to reduce these losses, improve the productivity of the extrusion process, and the overall quality of the material produced. One of the most important components of FE techniques for hot deformation is the type of flow stress model that is used in the simulations. In this investigation isothermal uniaxial compression testing was performed on cylindrical specimens of Ti-6Al-4V at temperatures ranging from 950 °C to 1200°C and strain rates of 0.1 s-1 to 50 s-1, to produce true stress against true strain and load against die travel curves which were subsequently used to develop a new specific flow stress model for use in hot deformation above the beta transus, which can ultimately be applied to the hot extrusion of Ti-6Al-4V. From analysis of this data it was concluded that flow softening and work hardening do not occur during deformation, and that low friction conditions exist between the material and the tooling. The activation energy for deformation was found to be 193178 J.mol-1, and the flow stress model was shown to give a good fit to the raw data at low strain rates, but this relationship broke down at higher strain rates. Finally the importance of generating a flow stress model specific to a particular operation, and set of experimental data, rather than relying on existing data available in the literature is demonstrated.
On the Solute Diffusion Length in the Interdependence Model: Dendritic versus Non-Dendritic Interface
Authors: Prasad Arvind , Yuan Lang , Lee Peter D. , Easton Mark , St John David
Published: August 2015

The Interdependence model currently uses an analytical expression for a moving planar interface to calculate the solute diffusion length designated as x’dl in the model. Upon nucleation within an alloy melt (i.e. when the solid embryo starts to grow), the interface grows with a spherical front which then breaks down into a dendritic interface. The time required for this breakdown is a subject for separate research. In this paper, we explore the validity of using a planar interface in the early stages of nucleation and growth of metal alloys as used in the Interdependence model. The diffusion field ahead of a planar interface, in theory, has an exponentially changing composition of infinite length. In the Interdependence model, x’dl is assumed to be where this exponentially decreasing composition profile in the liquid ahead of the interface (for k < 1) reduces to within 1% of a quantity proportional to the nominal alloy composition, C0, far from the interface. A numerical solidification model, μMatIC, is used to simulate the growth of a single grain with a dendritic interface in 2D and 3D. The numerical model is capable of generating the solute profile ahead of the growing grain which is used to evaluate the solute diffusion length that can be compared with the results obtained from the planar interface model. The comparisons were made with both 1% and 0.1% cut-off criteria. The results indicate that the 1% assumption being used in the planar front diffusion length calculation is a good approximation for the Interdependence model.
Optical Monitoring and Numerical Simulation of Temperature Distribution at Selective Laser Melting of Ti6Al4V Alloy
Authors: Zhirnov Ivan , Yadroitsava Ina , Yadroitsev Igor
Published: August 2015

Selective laser melting (SLM) is a modern method for producing objects with complex shape and fine structures in one working cycle from metal powders. Combination of the advanced technology of SLM with unique properties of Ti6Al4V alloy allows creating complex 3D objects for medicine or aerospace industry. Since properties of SLM parts depend on the geometrical characteristics of tracks and their cohesion, optical monitoring is actually used to for control the process. Temperature gradient determines the microstructure and mechanical properties of the SLM part, so studies about temperature fields are primarily important. On-line monitoring during laser scanning of Ti6Al4V alloy and formation of a single track in real-time with high-speed IR camera was studied. Numerical simulation allowed estimation the temperature distribution during processing. Conclusion regarding control system based on the online monitoring of deviations of the signal from IR camera during the SLM process was done.