scholarly journals Characterization of the Density and Spatial Distribution of Dispersoids in Al-Mg-Si Alloys

Metals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 26
Author(s):  
Magnus Remøe ◽  
Ida Westermann ◽  
Knut Marthinsen
Keyword(s):  
Spatial Distribution ◽  
Age Hardening ◽  
Careful Selection ◽  
Homogenization Procedure ◽  
Heating Rates ◽  
Spatial Uniformity ◽  
Nucleation Sites ◽  
Precipitation Behaviour ◽  
Selection Of

Al-Mg-Si alloys often contain small additions of, for example, Mn or Cr, to form dispersoids, which may act as nucleation sites for Mg2Si particles after homogenization. The purpose of adding Mn and Cr is to ensure a high density of uniformly distributed small β’-particles, which can be dissolved during further processing prior to the final age hardening step. However, their density and spatial distribution are critically dependent on the homogenization procedure. It is therefore important to have a robust and reliable method for assessing their spatial distribution. In the present work, an existing methodology for assessing spatial uniformity, the Global Shannon Entropy (GSE), was implemented and evaluated for different dispersoid structures characterized by scanning electron microscopy. This metric is highly dependent on the parameters used, but by careful selection of adequate parameters, it can be effective in detecting non-uniformity. An important weakness with the GSE was identified, and a modification to improve on the ability to differentiate degrees of non-uniformity is suggested. To evaluate the proposed methodology, the effect of heating rate on dispersoid precipitation behaviour during homogenisation of four Al-Mg-Si alloys with different Mn/Cr-content was investigated. In general, the dispersoid density increased with decreasing heating rates as longer times in the furnace resulted in particle coarsening. Slower heating rates were found to promote a more uniform dispersoid structure for most alloys investigated in this study. The metric with the new term demonstrated promising results, and improved the ability to differentiate degrees of spatial uniformity.

The Effect of Heating Rate on the Density and Spatial Distribution of Dispersoids during Homogenisation of 6xxx Aluminium Alloys

2016 ◽  
Vol 877 ◽  
pp. 322-327 ◽  
Author(s):  
Magnus S. Remøe ◽  
Knut Marthinsen ◽  
Ida Westermann ◽  
Ketill Pedersen ◽  
Jostein Røyset ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Heating Rate ◽  
Aluminium Alloys ◽  
Rapid Heating ◽  
Number Density ◽  
Heating Rates ◽  
Precipitation Behaviour ◽  
Quantitative Analyses ◽  
Mn Content

Two 6xxx alloys with different Mn-content have been homogenised in a furnace at 575 oC for 2 hours and 15 minutes. Three different heating rates to the homogenisation holding temperature were chosen, as this was expected to affect the precipitation behaviour of the dispersoids. The study focused on developing a reliable procedure for the characterization of the density and spatial distribution of dispersoids in aluminium alloys; both in terms of sample preparation, microscopic techniques and quantitative analyses of results. Scanning electron microscopy (SEM) has been used to evaluate the dispersoid characteristics for the different alloys and heating rates. The results indicate an increase in dispersoid number density and a more uniform distribution of dispersoids for the lowest heating rate, as compared to the more rapid heating rates, for the alloy with 0.05 wt% Mn. For the alloy with 0.15 wt% Mn the number density increased with the heating rate. This is suggested to be due to particle coarsening as an effect of the low heating rate where the samples spend longer time in the furnace.

Optimization of Ageing Parameters of a Low Nickel Maraging Steel

2010 ◽  
Vol 636-637 ◽  
pp. 471-477 ◽  
Author(s):  
M. Cabeza ◽  
G. Castro ◽  
P. Merino ◽  
G. Pena ◽  
M. Román ◽  
...  
Keyword(s):  
Maraging Steel ◽  
Structural Changes ◽  
Precipitation Hardening ◽  
Age Hardening ◽  
Scanning Calorimetry ◽  
Hardening Treatment ◽  
Depth Study ◽  
Final Selection ◽  
Selection Of

In the present work the age hardening parameters of a 14Ni (200) maraging steel are studied in order to optimize mechanical properties of the steel. The initial characterization of the as received solution annealed steel has been carried out by optical and scanning electron microscopy (LOM and SEM), and hardness measurements. To identify the structural changes during ageing, differential scanning calorimetry (DSC) tests were performed. Different time-temperature combinations were considered for the precipitation hardening treatment of as-quenched material samples. After hardness measurements, three of these treatments were selected for an in depth study. The obtained microstructure at the maximum hardness peaks then analysed (LOM, SEM and TEM) and mechanical behaviour (strength, toughness and wear resistance) was studied for the final selection of the age hardening conditions.

scholarly journals FROGs: a daily 1° × 1° gridded precipitation database ofrain gauge, satellite and reanalysis products

2019 ◽  
Author(s):  
Rémy Roca ◽  
Lisa V. Alexander ◽  
Gerald Potter ◽  
Margot Bador ◽  
Rômulo Jucá ◽  
...  
Keyword(s):  
South America ◽  
Daily Precipitation ◽  
Precipitation Extremes ◽  
Careful Selection ◽  
Large Ensemble ◽  
Rain Gauges ◽  
Large Spread ◽  
Global Land ◽  
Selection Of

Abstract. We introduce the Frequent Rainfall Observations on GridS (FROGS) database (Roca et al., 2019). It is composed of gridded daily precipitation products on a common 1° × 1° grid to ease intercomparison and assessment exercises. The database includes satellite, ground–based and reanalysis products. As most of the satellite products rely on rain gauges for calibration, unadjusted versions of satellite products are also provided where available. Each product is provided over its length of record and up to 2017 if available. Quasi-global, quasi-global land only, ocean only as well as tropical only and regional products (over continental Africa and South America) are included. All products are provided on a common netCDF format that is compliant with CF and AAC standards. Preliminary investigations of this large ensemble indicate that while a lot of features appear robust across the products, the characterization of precipitation extremes exhibit a large spread calling for careful selection of the products used for scientific applications. All datasets are freely available via an ftp server and identified thanks to the DOI: https://doi.org/10.14768/06337394-73A9-407C-9997-0E380DAC5598.

scholarly journals Methodology for selection of samples from borehole probe for technological characterization of iron ore

2014 ◽  
Vol 67 (3) ◽  
pp. 271-277
Author(s):  
Gésner J. I. dos Santos ◽  
Diniz T. Ribeiro ◽  
Carlos Alberto Pereira
Keyword(s):  
Spatial Distribution ◽  
Iron Ore ◽  
Mineral Processing ◽  
Statistical Analyses ◽  
Fast Analysis ◽  
Evaluation Team ◽  
Resources Evaluation ◽  
Mining Projects ◽  
Selection Of

The risks in the evaluation of mining projects are directly related to the probability of errors in the estimates, and, as the estimates are based on sampling results, this activity must be performed in a careful and planned way, to prevent surprises at the beginning of operation. To validate the representativeness of the borehole samples selected for the mineral processing studies, the geological resources evaluation team proposed a methodology based on the utilization of statistical analyses that, beyond considering the spatial distribution of the samples in the deposit, also assessed if they are representative of the populations under investigation. With this data, the geologist is able to make a fast analysis of the sampling's representativeness.

scholarly journals FROGS: a daily 1°  ×  1° gridded precipitation database of rain gauge, satellite and reanalysis products

2019 ◽  
Vol 11 (3) ◽  
pp. 1017-1035 ◽  
Author(s):  
Rémy Roca ◽  
Lisa V. Alexander ◽  
Gerald Potter ◽  
Margot Bador ◽  
Rômulo Jucá ◽  
...  
Keyword(s):  
South America ◽  
Daily Precipitation ◽  
Rain Gauge ◽  
Precipitation Extremes ◽  
Careful Selection ◽  
Rain Gauges ◽  
Large Spread ◽  
Global Land ◽  
Selection Of

Abstract. We introduce the Frequent Rainfall Observations on GridS (FROGS) database (Roca et al., 2019). It is composed of gridded daily-precipitation products on a common 1∘×1∘ grid to ease intercomparison and assessment exercises. The database includes satellite, ground-based and reanalysis products. As most of the satellite products rely on rain gauges for calibration, unadjusted versions of satellite products are also provided where available. Each product is provided over its length of record and up to 2017 if available. Quasi-global, quasi-global land-only, ocean-only and tropical-only as well as regional products (over continental Africa and South America) are included. All products are provided on a common netCDF format that is compliant with Climate and Forecast (CF) Convention and Attribute Convention for Dataset Discovery (ACDD) standards. Preliminary investigations of this large ensemble indicate that while many features appear robust across the products, the characterization of precipitation extremes exhibits a large spread calling for careful selection of the products used for scientific applications. All datasets are freely available via an FTP server and identified thanks to the DOI: https://doi.org/10.14768/06337394-73A9-407C-9997-0E380DAC5598.

Applications of Transmission Electron Microscopy in the Characterization of Metal Machinability

1968 ◽  
Vol 26 ◽  
pp. 442-443 ◽  
Author(s):  
L.E. Murr ◽  
A.B. Draper
Keyword(s):  
Electron Microscopy ◽  
State Physics ◽  
Test Material ◽  
Milling Machine ◽  
Rotary Table ◽  
Solid State Physics ◽  
Materials Properties ◽  
Transmission Electron ◽  
Selection Of

The industrial characterization of the machinability of metals and alloys has always been a very arbitrarily defined property, subject to the selection of various reference or test materials; and the adoption of rather naive and misleading interpretations and standards. However, it seems reasonable to assume that with the present state of knowledge of materials properties, and the current theories of solid state physics, more basic guidelines for machinability characterization might be established on the basis of the residual machined microstructures. This approach was originally pursued by Draper; and our presentation here will simply reflect an exposition and extension of this research.The technique consists initially in the production of machined chips of a desired test material on a horizontal milling machine with the workpiece (specimen) mounted on a rotary table vice. A single cut of a specified depth is taken from the workpiece (0.25 in. wide) each at a new tool location.

Caracterização da Peneira Média em Clones de Coffea canephora

REVISTA FIMCA ◽  
2018 ◽  
Vol 5 (2) ◽  
pp. 28-31
Author(s):  
Darlan Darlan Sanches Barbosa Alves ◽  
Victor Mouzinho Spinelli ◽  
Marcos Santana Moraes ◽  
Carolina Augusto De Souza ◽  
Rodrigo da Silva Ribeiro ◽  
...  
Keyword(s):  
Genetic Improvement ◽  
Block Design ◽  
Coffea Canephora ◽  
Coffee Production ◽  
Randomized Block Design ◽  
Significant Difference ◽  
The Mean ◽  
Four Blocks ◽  
Selection Of

Introdução: O estado de Rondônia se destaca como tradicional produtor de café, sendo o segundo maior produtor brasileiro de C. canephora. No melhoramento genético de C. canephora, a seleção de plantas de elevada peneira média está associada à bebida de qualidade superior. Objetivos: O objetivo desse estudo foi avaliar a variabilidade genética de clones de C. canephora para o tamanho dos grãos, mensurado a partir da avaliação da peneira média (PM). Materiais e Métodos: Para isso, foi conduzido ao longo de dois anos agrícolas experimento no campo experimental da Embrapa no município de Ouro Preto do Oeste-RO, para a avaliação da peneira média de 130 genótipos (clones) com características das variedades botânicas Conilon, Robusta e híbridos intervarietais. O delineamento experimental utilizado foi de blocos ao acaso, com quatro repetições de quatro plantas por parcela. Resultados: Não houve resultados significativos para a interação clones X anos, indicando uma maior consistência no comportamento das plantas ao longo do tempo. Porém foram observadas diferenças significativas para o tamanho dos grãos entre os genótipos avaliados, possibilitando selecionar genótipos superiores. Conclusão: Os genótipos agruparam-se em cinco classes de acordo com o teste de média, subsidiando a caracterização de um gradiente de variabilidade da característica avaliada ABSTRACTIntroduction: Coffea canephora accounts for approximately 35% of the world's coffee production. The state of Rondônia stands out as a traditional coffee producer, being the second largest Brazilian producer of C. canephora. In the classical genetic improvement of C. anephora, the selection of plants of high average sieve is associated with a drink of superior quality. Objectives: The objective of this udy was to evaluate the genetic variability of Coffea canephora clones for the agronomic medium sieve (PM). Materials and Methods: The experiment was conducted in the experimental field of Embrapa, municipality of OuroPreto do Oeste-RO, located at coordinates 10º44'53 "S and 62º12'57". One hundred thirty genotypes (clones) of botanical characteristics Conilon, Robusta and intervarietal hybrids were evaluated in the agricultural years 2013-2014 and 2014-2015. The experimental design was a randomized block design with four blocks and four plants per plot, spacing 3.5 x 1.5 meters between plants. Results: Significant difference was found for the grain size. According to the F test, at 5% probability, the genotypes were grouped into five classes according to the mean test. Conclusion: The results obtained subsidized the characterization of a variability gradient of the evaluated trait.

Afterword

2020 ◽  
pp. 680-683
Author(s):  
Janice L. Waldron ◽  
Stephanie Horsley ◽  
Kari K. Veblen
Keyword(s):  
Social Media ◽  
Media Use ◽  
Careful Selection ◽  
Social Media Use ◽  
Pedagogical Tools ◽  
The Future ◽  
User Data ◽  
Selection Of ◽  
Data Surface

We all feel the implications of the force of social media—for good and for ill—in our lives and in our professional world. At the time of this writing, Facebook continues with its struggle to “clean up its act” as more revelations surrounding breaches of trust and hacked user data surface in the news and various countries attempt to hold Facebook to account. Despite this, social media use continues to grow exponentially, and the potential for responsible, ethical, and transparent social media to transform the ways in which we interact with and learn from each other increase with it. As we wait to see what the future holds for social media in society, we are reminded once again that it is the careful selection of pedagogical tools such as social media, as well the guided awareness of the challenges and benefits of those tools, that remains constant, even as tools may change, disappear, or fall out of fashion.

Elaboration and Characterization of the Properties of Refractory Cr Base Alloys

2010 ◽  
Vol 72 ◽  
pp. 46-52 ◽  
Author(s):  
Laurent Royer ◽  
Stéphane Mathieu ◽  
Christophe Liebaut ◽  
Pierre Steinmetz
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Molten Glass ◽  
Energy Production ◽  
Creep Properties ◽  
Refractory Alloys ◽  
Industrial Use ◽  
Kinetics Of ◽  
Selection Of

For energy production and also for the glass industry, finding new refractory alloys which could permit to increase the process temperatures to 1200°C or more is a permanent challenge. Chromium base alloys can be good candidates, considering the melting point of Cr itself, and also its low corrosion rate in molten glass. Two families of alloys have been studied for this purpose, Cr-Mo-W and Cr-Ta-X alloys (X= Mo, Si..). A finer selection of compositions has been done, to optimize their chemical and mechanical properties. Kinetics of HT oxidation by air, of corrosion by molten glass and also creep properties of several alloys have been measured up to 1250°C. The results obtained with the best alloys (Cr-Ta base) give positive indications as regards the possibility of their industrial use.

scholarly journals Organelle Genetics in Plants

2021 ◽  
Vol 22 (4) ◽  
pp. 2104
Author(s):  
Pedro Robles ◽  
Víctor Quesada
Keyword(s):  
Rna Editing ◽  
Posttranscriptional Regulation ◽  
Genome Engineering ◽  
Plant Mitochondria ◽  
Plastid Dna ◽  
Chloroplast Genomes ◽  
Wide Range ◽  
Organelle Genetics ◽  
Selection Of

Eleven published articles (4 reviews, 7 research papers) are collected in the Special Issue entitled “Organelle Genetics in Plants.” This selection of papers covers a wide range of topics related to chloroplasts and plant mitochondria research: (i) organellar gene expression (OGE) and, more specifically, chloroplast RNA editing in soybean, mitochondria RNA editing, and intron splicing in soybean during nodulation, as well as the study of the roles of transcriptional and posttranscriptional regulation of OGE in plant adaptation to environmental stress; (ii) analysis of the nuclear integrants of mitochondrial DNA (NUMTs) or plastid DNA (NUPTs); (iii) sequencing and characterization of mitochondrial and chloroplast genomes; (iv) recent advances in plastid genome engineering. Here we summarize the main findings of these works, which represent the latest research on the genetics, genomics, and biotechnology of chloroplasts and mitochondria.

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