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By Q. Chen, J. H. Zhang, M. Zhang, F. M. Zheng, Y. J. Zhang

The characteristics of air bubbles and gas dispersion in KYF flotation cell are studied using the method of the point conductivity probe and CFD simulation. With increasing of speed, the velocities of air bubbles increase slowly and the distribution of diameters exhibits little change. With increasing of aeration rate, the gas holdup is increased. However, the velocities and diameters of bubbles have no great change. The CFD predictions on gas holdup have good agreement with the experiment results. The gas holdup distribution in the center section is revealed. The gas dispersion in the middle and upper part of flotation cell is uniform. It would be helpful for bubbles and solid particles collision. The gas holdup of the lower part of flotation cell is scarce, and it agrees with the observation in experiment. The gas would accumulate at the suction side of impeller blades, and it would decrease the power consumption. The rotating speed and aeration rate have great effect on gas dispersion. With increasing of aeration rate, the gas holdup of flotation cell will increase. The increasing of speed would improve gas dispersion. The results are expected to help to optimize the performances of KYF flotation cell.

Jan 1, 2015

By K. R. Barnard, K. D. Marte, T. V. Gamarano

"The first commercial scale application of CSIRO’s direct solvent extraction (DSX) technology has been in operation at the Boleo project in Mexico since December, 2015. In this application, DSX is a synergistic solvent extraction system consisting of the extractants LIX 63 and Versatic 10 for recovery of cobalt and zinc from a solution background of manganese, magnesium, and calcium. Key operating parameters such as metal extraction, phase disengagement and extractant stability are summarized and discussed in this paper.INTRODUCTION Commissioning of the Boleo processing plant, located on Mexico’s Baja peninsula, began with the copper circuit starting in late 2014, with first copper cathode production achieved in January, 2015. The cobalt and zinc circuits began commissioning in December, 2015 with first zinc sulphate monohydrate (ZSM) and cobalt cathode production achieved in February and April, 2016 respectively. The Boleo project flow sheet and development has been described in detail in previous publications (Dreisinger, et al. 2005; Dreisinger, Baxter, & Molnar, 2006; Dreisinger, et al. 2008; Dreisinger, et al. 2009) and is summarized schematically in Figure 1. Boleo is a mixed oxide/sulphide Cu-Co-Zn-Mn high clay deposit that is processed in a whole ore, atmospheric, oxidative and reductive, sulphuric acid/seawater leach. Copper is recovered as cathode by conventional solvent extraction and electrowinning. Cobalt and zinc are recovered, from a solution background of manganese, magnesium, and calcium, by CSIRO’s synergistic solvent extraction technology Direct Solvent Extraction (DSX). Cobalt and zinc are bulk stripped from the DSX circuit and then further purified by phosphinic acid solvent extraction to produce zinc sulphate monohydrate granules via spray dried granulation and cobalt cathode rounds via divided cell electrowinning."

Jan 1, 2017

By Edouard Asselin, Tasawar Javed

The precipitation of hematite from ferric sulphate - cupric sulphate - lithium chloride acidic solutions was studied in a batch reactor. The effect of several variables on the extent of hematite precipitation as well as on its crystallinity and purity was investigated. The variables studied include: initial ferric concentration (1.5 - 30 g/L), retention time (0 - 12 h), initial sulphuric acid concentration (0 - 30 g/L), temperature (150 - 220 °C) and chloride concentration (0 - 25 g/L). The results show that hematite is preferentially precipitated at lower initial iron concentrations. Longer retention times increased the fraction of hematite in the precipitates but did not affect its crystallinity to a significant extent. On the other hand, higher temperatures increased the purity and crystallinity of the hematite. At lower acid concentrations hematite and goethite were precipitated. However, only hematite was precipitated when the initial acid concentration was > 12.5 g/L. Better crystalline hematite was formed at lower acidities. Increasing chloride concentration increased the amount of hematite and decreased the amount of iron sulphate hydroxide phases, but did not affect the crystallinity of the hematite.

Jan 1, 2015

By S. McPherson, M. Chalkley, R. Ellenwood, W. Nicot

"The Moa JV was formed in December 1994 as a 50/50 joint venture between Sherritt Inc. and General Nickel Company S.A. of Cuba. The joint venture consists of the mine and Pedro Sotto Alba processing plant in Moa, Cuba and the Corefco refinery in Fort Saskatchewan, Alberta, Canada. Throughout its now nearly 23-year history, the Moa Joint Venture has faced a number of global, operational and process challenges. Global challenges have included high input costs such as for fuel oil and sulphur, as well as low nickel prices. Operational and process challenges have included increasing ore haulage distances, decreasing ore Ni + Co grades, and increasing ore impurity contents. For example, increases in impurities such as Mg and SiO2 in the ore result in increasing acid demand in leaching and decreasing solids content of preheated leach feed slurry, respectively. In spite of these challenges, the mixed sulphide production capacity from the Moa Joint Venture has increased from 12,500 to 37,000 t/y Ni + Co since 1994 by judiciously targeting expansion projects and by continuously performing process and operational improvements.INTRODUCTION The Pedro Sotto Alba high pressure acid leach (HPAL) plant at Moa Bay, Cuba has a long history (Maslenitzkiy, 1969; Chalkley, 1996; Carlson, 1960; Roy, 1961; Carlson 1961). The plant was constructed by Moa Bay Mining Company and started up in late 1959 after several years of process development by Freeport Nickel Company, including operation of a 10 t/d plant in Hoskins Mound, Texas and a 50 t/d plant in Port Nickel, Louisiana (Southwick, 2004), as well as development work by Chemical Construction Company (Chemico) to precipitate metal sulphides (Roy, 1955a; Roy, 1955b). The Moa plant had an original reserve of 50,000,000 t of ore, graded at 1.35 wt% Ni, 0.146 wt% Co, 3.70 wt% Si, 1.00 wt% Mg and 4.5 wt% Al. At original design rates of 2,000 kt/y of ore, the design capacity of the plant was around 25,000 t/y Ni + Co as a mixed sulphide product, which would be shipped to the Port Nickel Refinery in Louisiana for processing. In 1960, the plant changed ownership and was restarted in 1961 under Cuban management. Between 1961 and 1989, the plant was also supported by involvement from the former USSR, supplying spare parts and consumables. In 1994, Sherritt Inc. partnered with the General Nickel Co. S.A. of Cuba and formed the Moa Joint Venture. This joint venture includes the mine and Pedro Sotto Alba HPAL processing plant in Cuba and the Corefco refinery in Fort Saskatchewan, Alberta, Canada. Under this partnership, ore is processed in Cuba to produce a nominally 55 wt% Ni and 5 wt% Co mixed sulphide product that is shipped to Canada and processed by Corefco to produce class 1 nickel, high grade cobalt and byproduct ammonium sulphate fertilizer."

Jan 1, 2017

By Richard D. Moffett

The MineSight® Implicit Modeler arms geologists, engineers and surveyors with a better approach to 3D modeling. Use the tool to quickly retrieve a 3D wireframe from drillhole data and onscreen interpretation. Generate faster and more informed decisions to guide future work and improve reproducibility of results. Implicit Modeling is a mathematical surface fitting method that interpolates points to give a smooth and realistic fit. Control results by mixing planar, sectional and non-orthogonal polygons or polylines, as well as drillhole information to create solids or surfaces. The outcomes are particularly valuable to identify ore body trends, generate 3D contours of drillhole intercepts, or produce cut-off 3D maps. MineSight Implicit Modeler (MSIM) is fully integrated in MineSight?s robust and versatile suite of products, allowing you to interpret, interpolate and calculate while moving between applications. It connects seamlessly with the MineSight Torque SQL database, offering access to extensive filtering options. MSIM makes modeling much faster, allowing geologists more time to analyze data and test theories. The presentation will reveal how MSIM complements MineSight?s geomodeling workflow.

May 1, 2013

By P. C. M. Knops, K. Rijnsburger, R. M. Santos

To overcome the challenges of mineral CO2 sequestration, this work utilizes a unique proprietary Gravity Pressure Vessel (GPV) reactor technology, and focuses on reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy. Here, laboratory-scale tests of the envisioned process was performed in tubular and continuously stirred tank reactor (CSTR) autoclave reactors. The mineral used was Olivine (~Mg1.6Fe2+0.4(SiO4) + ppm Ni/Cr), although asbestos, steel slags and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties was tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers), solids loading, and mixing rate. The products (carbonates, amorphous silica and Chromite) were physically separated (based on size, density and magnetic properties), characterized (for chemistry, mineralogy and morphology) and tested in intended applications (e.g. as pozzolanic carbon-negative building material). Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable hydrometallurgical process.

Jan 1, 2015

By A. McLean, L. Gao, Z. Shi, Y. D. Yang, K. Chattopadhyay, G. F. Zhang

Levitation melting of metals is one of the emerging applications of magnetic and electric fields in liquid metal refining. The varying magnetic field generates induced current inside the metal droplet and leads to the Joule heating effect and Lorentz force against gravity. This contactless process can avoid contamination from the crucible and can be used to produce high-purity materials. Visualization of the levitation melting process is difficult, and thus generally investigated by mathematical modeling. In the present study, a three-dimensional mathematical model of metal levitation was developed using finite element method for proper understanding of the levitation process. The effects of harmonic magnetic field frequency, coils power input, and sample size on levitation nickel droplet were investigated. Temporal evolution of temperature fields were predicted directly though the model. Levitation and balance condition of the droplet were investigated as well.

Jan 1, 2015

By A. M. L. Cushing, S. Kelebek

Presently, adsorption is one of the effective methods of removing toxic contaminants from waste waters. The contaminants from metal mining industrial operations include an effluent water containing various types of heavy metal species at concentrations beyond the maximum allowable limits, which are 0.5 ppm and 0.3 ppm for nickel and copper species, respectively. Adsorption behavior of copper ions pre-chelated with diethylenetriamine (DETA) and triethylenetetramine (TETA) onto natural bentonite and peat has been investigated. Both natural bentonite and peat was found to be capable of removing these copper-polyamine complexes from aqueous solutions relevant to process water effluents. However, the adsorption capacity of bentonite was significantly higher than that of peat. Two models were used to study the adsorption kinetics: a pseudo-first-order rate expression and a pseudo-second-order rate expression. For both adsorbents, the data conformed best to the pseudo-second-order rate expression. Representation of the experimental data through adsorption models was also investigated. Out of the four cases considered, namely, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms, it was found that for both bentonite and peat, the copper polyamine adsorption data conformed best to the Dubinin-Radushkevich adsorption model. The Langmuir model also represents the bentonite-copper polyamine adsorption system reasonably well as the second best case, suggesting that the amount adsorbed on bentonite might be a monolayer with strong affinity.

Jan 1, 2015

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By M. Leroux, C. J. Martin, S. R. Rao, J. A. Finch

"The effect of nitrogen on the flotation separation of sulphides from complex ores from Brunswick Mining and Smelting (New Brunswick) and Mattabi Mines (Ontario) was investigated. The most significant finding was enhanced pyrite floatability after as little as 3 minutes nitrogen conditioning. This was used in a novel sphalerite/pyrite separation process developed on the Brunswick ore. After aeration and Cu/Pb bulk flotation in air using xanthate the slurry was nitrogen conditioned, xanthate added and the pyrite floated in nitrogen. As an example up to 70% pyrite recovery with about 20% sphalerite recovery was achieved. Sphalerite was recovered from the pyrite tailings and the pyrite concentrate by copper-activation, raising the pH to 10 and floating in air. About 65-70% recovery at 35-40% Zn grade was achieved compared to 25% Zn grade by the conventional route. The process offers a promising alternative to current practice which seeks to depress pyrite at all stages. A possible mechanism of the effect of nitrogen is presented. INTRODUCTIONUse of gases other than air in froth flotation has been reported from time to time. [Podobnik and Shirley, 1982; Lin and Metzer, 1975]. Of all the gases, nitrogen would appear to hold the greatest practical promise because of its easy availability and chemical inertness. It is used in froth flotation in chalcopyrite-molybdenite separation [Redfearn, 1983]. The use of nitrogen in polysulphide chalcopyrite. this case is mainly to reduce the oxidation of a compound (Nokes reagent) used as a depressant for There is no reported use of nitrogen in the flotation of other sulphide minerals."

Jan 1, 1988

By F. Rashchi, A. Ghahreman, J. Moghaddam, S. Karimi

"In this work, the kinetics of ferric-ferrous redox reaction on a passivated sphalerite electrode is studied by the application of chronoamperometry method in 0.5 mol L-1 H2SO4 solution. The electrochemical behaviour of ferric and ferrous couple was investigated on two sphalerite minerals acquired from two different geological regions (Iran and Canada). The carbon paste electrode (CPE) of sphalerite was initially prepared and passivated in 0.5 mol L-1 H2SO4 solution and after reaching the steady-state condition, ferric and ferrous sulfate solution was added. The registered current density differences between the current density of the passivated electrode and that of the electrode in the iron salts added solution were interpreted for kinetics of ferric-ferrous reduction-oxidation reaction. The equilibrium potential for ferric-ferrous couple on sphalerites surface was about 500 mV vs. Ag/AgCl. The exchange current density (i0) for ferric-ferrous redox reactions on the sphalerite samples had the same magnitude of 10–6 A cm–2. The electrochemical impedance spectroscopy (EIS) measurements at 550 mV vs. Ag/AgCl illustrated that sphalerite oxidation was controlled by two charge transfer process in both of Fe-free and Fe-containing solutions. The charge transfer resistance remarkably decreased when Fe salts added to the 0.5 mol L-1 H2SO4 solution, owing to the ferric-ferrous redox reactions being the predominant reactions on sphalerite surface.INTRODUCTION Direct atmospheric leaching processes for sphalerite concentrates are performed by reduction of an oxidant (e.g. ferric ion and oxygen) and oxidation of sphalerite to zinc ions. Oxygen could be an oxidizing agent as well, but the concentration of oxygen is very low in the solution. The role of ferric ions is predominate in this oxidation (Babu, Sahu, & Pandey, 2002). The oxidation reaction for sphalerite in the presence of ferric in can be presented as follows (Lampinen, Laari, & Turunen, 2015):"

Jan 1, 2017

By L. Lorio, B. Hilscher, P. Nayak, N. Yoon

"Mining has been a staple to technological advancement ever since the dawn of time. By harnessing the different physical and chemical properties that each mining commodity brings to the table, more and more innovation is developed and manufactured. As these non-renewable resources continue to be extracted, the industry as a whole faces a challenge in finding the next economical deposit as well as declining grade at the current operations. By means of pre-concentration, ore sorting aims to separate the barren material from the valuable ore to reduce energy consumption and tailings generation, while increasing the feed grade, concentrate grade, mill recovery, and revenue. In addition, ore sorting allows the modification of deposit geometallurgy in order to allow the creation of an optimal mill feed. This paper evaluates the applicability and challenges of ore sorting by utilizing the results from four different mines, and reviews them in detail. The mines include one underground and three open pit mines that are precious metal operations. In order to understand the applicability of ore sorting in these operations, initial rock-by-rock test results and different types of assays (atomic adsorption [AA], inductively coupled plasma [ICP], and fire assay) are utilized. Using the assay results, the grade recovery curves for ore sorting are generated and they are further improved by using and developing an ore sorting algorithm, which is discussed in this paper. The application and evaluation of ore sorting in greenfield and brownfield properties will also be discussed. The state of the art ore sorting technologies for both rock-by-rock and bulk sorting are also reviewed in this paper. The future technologies on the horizon, including different combinations of sensors, are explained. The sorting technologies include X-ray transmission (XRT), X-ray fluorescence (XRF), colour, infrared, electromagnetic, and laser induced breakdown spectroscopy (LIBS)."

Jan 1, 2017

By Christiaan Zeilstra, Jan van der Stel, Koen Meijer, Gerard Louwerse, Tim Peeters

The steel industry is producing about 5% of the world wide CO2 emission. Therefore the European steel industry has defined a research program to reduce the CO2 emission by 50% per ton: ULCOS. Since its start in 2004 ULCOS has identified four technologies for further development. Two of these technologies which produce liquid hot metal are discussed. The ULCOS blast furnace is based on recycling of decarbonated topgas and the capture and storage of CO2. The concept has been demonstrated during three campaigns at LKAB EBF in Luleå, Sweden. The smelting reduction process HIsarna is a combination of the cyclone-technology and Hismelt. The process has been demonstrated successfully in four campaigns at a pilot installation on the IJmuiden steelmaking site.

Jan 1, 2015

By I. Caraconcea, M. Cousineau, S. Gariepy

"Several base metal plants operate in low grade/high tonnage conditions which impose strict cost control on all fronts for their operations to remain profitable. This leads to decisions regarding plant design, procurement, operations and maintenance that often favor cost minimization over value optimization. This may hinder the representativeness of the metal accounting systems while this should be a priority in a low margin environment. Such poor representativeness not only creates confusion in plant scheduling but can also hide suboptimal metallurgical performance. Furthermore, this situation can run undetected for a while since one dominant feature of a poor metal accounting system is its poor self-awareness. During their practice, authors have particularly identified measurement bias and reproducibility, as well as their impact on metal recoveries as areas of concern. These issues have not been extensively reviewed in the specific context of precious metals in base metal plants. Pragmatic solutions are proposed either at the design stage for a new project or to retrofit an actual operation. These solutions should be based on a business analysis that set a value of information matching the contribution of precious metals as well as the potential to use such information to act toward increasing plant profitability. Conclusions are that trade-offs are an inherent part of the design/audit/retrofit of any metal accounting system in any plant processing either base or precious metals. However, compromises must be evaluated on economic/technical ground.INTRODUCTION Every mineral processing plant must produce metal accounting reports (Morrison, 2008) where estimated saleable metal flows and inventories are published. These metal accounting reports are delivered to a variety of stakeholders who use them for internal management purposes (day-to-day plant production planning, plant operation optimization, capital spending, etc.) as well as for external management (royalty settlements, tolling agreements, etc.). Hence, there should be no doubt that state of the art metal accounting is instrumental for mining companies to reach and sustain high-quality corporate governance (Gaylard, Randolph, & Wortley, 2014). However, producing a metal accounting report involves much more than just printing it (Lachance, Leroux, & Gariépy, 2015a). The underlying metal accounting system (Figure 1) is responsible not only for the reliable production of the metal accounting reports but also for the quality of the outcome. As such, the crucial tasks of its design/audit/retrofit should neither be seen as ancillary nor be left as an afterthought."

Jan 1, 2017

By D. Shen, J. Cheung

Variable reactance arc control by the SPLC (Smart Predictive Line Controller) has been installed at many different mining sites and steel processing plants around the world. Since its first installation 18 years ago, many advances have been made to both the technology, and to its integration with furnace processes and plant operations. The SPLC has helped to improve electric arc furnace stability by reducing electrode movement while maintaining flat line arc power. Stable furnace operation at higher average power increases productivity. This paper summarizes the progression of electro-technology at Hatch since the 1970s, including fixed and variable reactance, digital electrode regulation, and fast variable speed hydraulics for Soderberg electrode, as demonstrated and benchmarked through projects and lessons learned over the years.

Jan 1, 2015

By C. Schmidt, M. Kohnk, C. Siemers, J. Kiese

The application of conventional titanium alloys is limited to 550°C due to their poor oxidation resistance. In addition, severe grain growth is observed in single-phase titanium alloys in long-term runs at elevated temperature leading to a degradation of their mechanical properties. In exhaust applications in automotive or aerospace engineering, products are often manufactured by cold-deformation like deep-drawing or rolling which is normally difficult in oxidation-resistant titanium alloys due to the presence of titanium-silicides. Therefore, in the current study, titanium alloys based on CP Titanium Grade 1S (soft grade) were developed showing (1) improved oxidation resistance due to a concerted addition of silicon, iron and niobium, (2) microstructure stability by the precipitation of hafnium-silicides mainly on the grain boundaries and (3) good cold-deformation properties. The industrial production route was developed so that the new class of Ti-Si-Fe-Nb-Hf-alloys is now ready for application in exhaust systems of planes or cars at minimum 800°C.

Jan 1, 2015

By M. Epiney, A. Ghahreman, R. Kim1and

"In the presence of sulfidic refractory ores, increasing the dissolved oxygen (DO) concentration can positively affect the gold leaching rate. To identify the role of DO in gold cyanidation, electrochemical behavior was studied in the presence of 3 different ores. Sample 1 was a low sulfide pyrite ore, contained 5.14% pyrite, 0.19% galena and 3.09% S. Sample 2 was a pyriticore as well, contained more sulfide as 8.35% S, and 12.4% of pyrite. Sample 3 was a tailing of silicate gold ore, still containing75 g/tAu, 0.13% Pb and 0.18% S. Gold cyanidation kinetics were studied by cyclic voltammetry (CV) and chronoamperometry tests. With sample 1, the gold oxidation peak current density from CV curve was increased to 1.38mA/cm2under oxygen injection, while it was only 0.66 mA/cm2with air injection. From chronoamperometry test, the reaction rate was also faster under oxygen injection. Sample 2 showed similar behavior with sample 1, but the gold oxidation peaks higher than sample 1, i.e. 1.75 and 2.27 mA/cm2, under air and oxygen injection, respectively. However, it seemed that the gold oxidation was impeded by sulfide ions for a longer period. In the presence of sample 3, the gold oxidation peak was the highest among three ores –2.75mA/cm2under oxygen injection, because of its lowest sulfide content. However, from chronoamperometry test, it was also shown that the gold oxidation was impeded because of a significant amount of Pb in the ore sample.INTRODUCTIONIt is well known that gold is leached under oxidative condition (Marsden &House, 2006). Through the most representative and oldest gold leaching technique, cyanidation, more than 90% of gold can be selectively leached from an ore. According to Elsner’s equation, gold is leached in cyanide solution by forming cyanide complex [Au (CN)2–], and oxygen is consumed as an oxidant(Eq. 1)."

Jan 1, 2017

By R. O. Suzuki, S. Natsui, R. Nashimoto, T. Kumagai, T. Kikuchi, H. Takai

A newly developed computational fluid dynamics model based on a multi-phase particle simulation is presented for predicting the entrainment behavior of liquid metal into slag due to rising single bubble. By comparing results calculated using this model against experimental data, it was found that the transient behavior of bubbles and the two immiscible liquids can be accurately estimated by this method. The rupturing of the thin water film surrounding the bubble was less reliably predicted, but this 3-dimensional unsteady numerical model still nevertheless provides valuable new information for directly predicting the change in the liquid-liquid interface over time. This model predicted the Young-Laplace pressure, and the interface shape was simulated with volume conservation using this model as opposed to the conventional particle method. This simulation model can calculate both of dispersed phase and continuous phase seamlessly.

Jan 1, 2015

By Eiichi Sato, Koichi Kitazono, Hiroshi Masuda, Kenta Higane

"The present study investigated the low-temperature creep mechanisms in ultrafine-grained (UFG) aluminum manufactured by accumulative roll bonding. UFG aluminum with grain size 0.39 µm showed steady state creep even at room temperature under low stresses as confirmed by the creep curves in the strain rate–strain plot. The low-temperature behavior was divided into four regions by three distinctive stresses, sI, sII and sIII: sI (=45 MPa) is denoted as the micro-yielding stress with which dislocations start movement, sII (=85 MPa) the dislocation-multiplication stress above which dislocations multiply with creep deformation, and sIII (=171 MPa) the conventional yield stress above which macroscopic plastic strain is generated. During low-temperature creep, below sI, negligible plastic strain is generated. Between sI and sII, creep deformation with stress exponent 2.5 occurred, which is accommodated by dislocation absorption into grain boundary and grain boundary sliding, similarly to the low-temperature creep of HCP metals. Between sII and sIII, creep deformation with stress exponent 7.0 occurred, whose mechanism is similar to the low-temperature creep of coarse-grained aluminum. Above sIII, power-law breakdown occurred.INTRODUCTIONIt is well understood that the creep deformation brings about at high homologous temperatures (T/Tm) of >0.4, where Tmis the melting point, with diffusion processes. Recently, the importance of aluminum is increasing for cryogenic temperature parts such as a metallic liner or a cap in high pressure-hydrogen vessels, and the presence of creep behavior in aluminum at room temperature has become recognized (Matsunaga, 2013;Kassner, 2015).In HCP metals and alloys, especially intitanium, steady-state creep behavior appears at room temperature with apparent activation energy of1/10 of that for self-diffusion(Neeraj, 2000; Matsunaga, 2009).On the other hand, Kassner (2015) claims that aluminum shows creep behavior at room temperature with apparent activation energy of 4/5of that forself-diffusion, but never reaches the steady state. We should note that it is derived from the data obtained from short-term creep tests of few hour, and Matsunaga (2013) already claimed the presence of steady state in room temperature creep in aluminum with activation energy of 1/5of that for self-diffusion.The mechanisms for low temperature creep are considered different between HCP and FCC metals: in HCP metals, grain boundary sliding is observed and is thought to accommodate piled-up dislocations at grain boundaries through absorbing them. The so-called slip-induced grain boundary sliding occurs with low number of activated slip systems(Matsunaga,2009).On the other hand, in FCC metals, many activated slip systems bring about work hardening with dislocation cell structure formation. In the initial stage of creep, it results in primary creep (Kassner, 2015), but Matsunaga (2013) claimed that once the annihilating of a cross-slipped dislocation to another reaches balance, steady state is established. It has been, however, strongly required to show more convincing experimental verification for the presence of steady state in FCC metals at low temperature."

Jan 1, 2018