The document summarizes a study on grain refinement in 0.16C steel through subcritical processing involving heavy deformation. Samples underwent hot torsion deformation at 685°C with strain rates of 1.0, 0.5, and 0.1 s-1. Microstructural analysis found the final microstructure was recrystallized with an average grain size of 1 μm. Three factors were found to contribute to the ultrafine grains: continuous dynamic recrystallization, rotation and breaking of initial boundaries, and cementite particles interfering with subgrain rotation and growth.
This document investigates obtaining ultrafine grains in low carbon steel through thermo-mechanical treatment in the ferrite domain. A low carbon steel with dispersed globular cementite was heavily deformed at 685°C at strain rates from 0.1-1 s-1. Regardless of route to spheroidize carbides, flow stress curves displayed an initial hump then extensive softening and steady state. Microstructural evolution was observed, with ferrite nucleating preferentially at defects. Both heavy deformation and high strain rates increased defects and bands, contributing to dynamic recrystallization and formation of ultrafine ferrite grains less than 2 μm on average. Continuous dynamic recrystallization during deformation led to the
This document investigates the effect of cementite particles on microstructure refinement and formation of high angle boundaries in low carbon steel. Warm deformation tests were conducted on a 0.16C steel and an ultra-low carbon steel up to a strain of 5 at 685°C and 0.1 s-1 strain rate. Electron backscatter diffraction analysis showed that cementite precipitation and ferrite recrystallization led to the formation of high angle boundaries and grain refinement during subcritical deformation. Flow stress was higher for the 0.16C steel due to cementite particles anchoring grain boundaries.
In 2010, Vitol Group's total energy volumes reached 394 million metric tonnes and turnover was $195 billion, up from $191 billion in 2009. Crude oil accounted for 74.8% of turnover, followed by gasoline and naphtha at 37.2%, and gas oil and jet fuel at 29.2%. Vitol's equity basis CO2 emissions were 103,785 tonnes from their E&P division with an efficiency of 0.0029 tonnes of CO2 per cubic meter, 160,558 tonnes from their VTTI division with an efficiency of 0.0284 tonnes of CO2 per barrel, and 3,814 tonnes from business travel. Spot crude prices increased from a
This document discusses how cost curves can be used as a business communication tool. It provides examples of cost curves showing the relative cost positions and profitability of competitors within different industries. Cost curves visually depict variables like production costs, price ranges, market share and margins in a simple way that is more impactful than words alone. The document encourages using a provided Excel macro to easily create cost curves for strategic business presentations and analysis.
Spatial and Temporal Expression of a Citrate Permease and Aluminium-induced C...CIAT
1) The document examines the spatial and temporal expression of a citrate permease gene (PvMATE) and aluminum-induced citrate exudation in common bean roots.
2) Results show that PvMATE is strongly expressed at the root tip, correlating with high citrate exudation in this region. Citrate exudation also remains substantial in the elongation zone.
3) Aluminum treatment induces expression of the STOP1 transcription factor before enhanced expression of PvMATE, indicating STOP1 regulates PvMATE. Citrate exudation follows a cascade of events involving Al signal reception, STOP1 activation, and PvMATE expression to maintain root growth under aluminum
This document shows a map of southern Alabama counties with data points marking counts of Chinese tallow trees. A legend explains that the data points represent counts of Chinese tallow trees conducted at stations across the region. A line graph overlays the map comparing the Chinese tallow tree counts to population density by census block from 2004. The map is titled "Chinese Tallow vs. 2004 Population" and is credited to Brian C. Averitt from November 2007.
Our design seeks to connect low-income residents in the Hunts Point neighborhood of New York City with healthy, affordable food from small and mid-size regional farms by drawing from several relevant precedents. These precedents include wholesale markets that connect farmers with distributors, distributors that deliver regional foods, collective purchasing models that allow discounts through group buying power, and cohousing communities that share meal preparation responsibilities to reduce costs. By integrating aspects of these precedents, our design aims to increase access to local, healthy foods for low-income communities.
The document discusses Petrobras' refining, transportation, and petrochemicals business segments. It notes that Petrobras has rapidly grown its proved oil reserves through deepwater discoveries. It also discusses how the growing Brazilian domestic market provides an attractive opportunity to monetize some of Petrobras' reserves due to Brazil's low per capita oil consumption and projected consumption growth. Additionally, it mentions that new refineries planned by Petrobras will produce higher value-added oil products and that both existing and new refineries are expected to become more productive over time.
This document investigates obtaining ultrafine grains in low carbon steel through thermo-mechanical treatment in the ferrite domain. A low carbon steel with dispersed globular cementite was heavily deformed at 685°C at strain rates from 0.1-1 s-1. Regardless of route to spheroidize carbides, flow stress curves displayed an initial hump then extensive softening and steady state. Microstructural evolution was observed, with ferrite nucleating preferentially at defects. Both heavy deformation and high strain rates increased defects and bands, contributing to dynamic recrystallization and formation of ultrafine ferrite grains less than 2 μm on average. Continuous dynamic recrystallization during deformation led to the
This document investigates the effect of cementite particles on microstructure refinement and formation of high angle boundaries in low carbon steel. Warm deformation tests were conducted on a 0.16C steel and an ultra-low carbon steel up to a strain of 5 at 685°C and 0.1 s-1 strain rate. Electron backscatter diffraction analysis showed that cementite precipitation and ferrite recrystallization led to the formation of high angle boundaries and grain refinement during subcritical deformation. Flow stress was higher for the 0.16C steel due to cementite particles anchoring grain boundaries.
In 2010, Vitol Group's total energy volumes reached 394 million metric tonnes and turnover was $195 billion, up from $191 billion in 2009. Crude oil accounted for 74.8% of turnover, followed by gasoline and naphtha at 37.2%, and gas oil and jet fuel at 29.2%. Vitol's equity basis CO2 emissions were 103,785 tonnes from their E&P division with an efficiency of 0.0029 tonnes of CO2 per cubic meter, 160,558 tonnes from their VTTI division with an efficiency of 0.0284 tonnes of CO2 per barrel, and 3,814 tonnes from business travel. Spot crude prices increased from a
This document discusses how cost curves can be used as a business communication tool. It provides examples of cost curves showing the relative cost positions and profitability of competitors within different industries. Cost curves visually depict variables like production costs, price ranges, market share and margins in a simple way that is more impactful than words alone. The document encourages using a provided Excel macro to easily create cost curves for strategic business presentations and analysis.
Spatial and Temporal Expression of a Citrate Permease and Aluminium-induced C...CIAT
1) The document examines the spatial and temporal expression of a citrate permease gene (PvMATE) and aluminum-induced citrate exudation in common bean roots.
2) Results show that PvMATE is strongly expressed at the root tip, correlating with high citrate exudation in this region. Citrate exudation also remains substantial in the elongation zone.
3) Aluminum treatment induces expression of the STOP1 transcription factor before enhanced expression of PvMATE, indicating STOP1 regulates PvMATE. Citrate exudation follows a cascade of events involving Al signal reception, STOP1 activation, and PvMATE expression to maintain root growth under aluminum
This document shows a map of southern Alabama counties with data points marking counts of Chinese tallow trees. A legend explains that the data points represent counts of Chinese tallow trees conducted at stations across the region. A line graph overlays the map comparing the Chinese tallow tree counts to population density by census block from 2004. The map is titled "Chinese Tallow vs. 2004 Population" and is credited to Brian C. Averitt from November 2007.
Our design seeks to connect low-income residents in the Hunts Point neighborhood of New York City with healthy, affordable food from small and mid-size regional farms by drawing from several relevant precedents. These precedents include wholesale markets that connect farmers with distributors, distributors that deliver regional foods, collective purchasing models that allow discounts through group buying power, and cohousing communities that share meal preparation responsibilities to reduce costs. By integrating aspects of these precedents, our design aims to increase access to local, healthy foods for low-income communities.
The document discusses Petrobras' refining, transportation, and petrochemicals business segments. It notes that Petrobras has rapidly grown its proved oil reserves through deepwater discoveries. It also discusses how the growing Brazilian domestic market provides an attractive opportunity to monetize some of Petrobras' reserves due to Brazil's low per capita oil consumption and projected consumption growth. Additionally, it mentions that new refineries planned by Petrobras will produce higher value-added oil products and that both existing and new refineries are expected to become more productive over time.
El documento presenta una serie de ejercicios relacionados con el cálculo de velocidad, rapidez y distancia en movimientos rectilíneos uniformes. Se explican las fórmulas necesarias para resolverlos y se dan los pasos de cálculo. Luego, se plantean 13 ejercicios resueltos sobre distintos escenarios de movimiento como pelotas, abejas, trenes y automóviles, calculando magnitudes como velocidad, rapidez y tiempo en función de la distancia y el tiempo dados.
El documento habla sobre un slidecast. En pocas palabras, un slidecast es una presentación en formato digital que combina diapositivas con una grabación de audio o video. El slidecast permite al creador grabar su presentación y compartirla con otros de forma dinámica.
The document summarizes analysis of labor data from the Bureau of Labor Statistics for Iowa from 2006-2015. Key points:
- Data was downloaded, cleaned, filtered to only include Iowa data, and concatenated into a single dataset for analysis.
- Occupations were clustered and categorized into 3 groups: Professional, Manual Labor, and Personal Services. Geographical areas were also grouped.
- Analysis found higher salaries in college towns and metro areas for professionals, with salaries exceeding $60k recently. Median incomes were highest for professionals, followed by manual labor, and lowest for personal services statewide.
- Salary distributions were explored, finding the gap between lower and higher salaries growing for most areas and occupations, particularly
O documento apresenta 60 exercícios de combinatória e binômio de Newton envolvendo combinações, permutações e cálculos de possibilidades de agrupamentos de elementos respeitando diferentes restrições. Os exercícios abordam temas como agrupamentos de livros, pessoas, letras do alfabeto, formação de comissões respeitando gênero e profissão, construção de figuras geométricas a partir de pontos e cálculo de diagonais de polígonos e sólidos geométricos regulares.
Brandon Garcia has over 10 years of experience in various fields including information technology, customer service, sales, marketing, and construction crew leadership. He is currently working to obtain 10 IT certifications through My Computer Career. Previously he has held positions such as general manager of a sports bar and bowl, marketing director, pipe fitter crew lead, and sales roles for fitness memberships and telemarketing.
Este documento describe dos grandes conflictos en Europa del siglo XX: las revoluciones rusas de 1905-1917 y la Primera Guerra Mundial de 1914-1918. Explica las causas profundas económicas, políticas y sociales de ambos eventos, incluyendo las rivalidades imperialistas, el nacionalismo y la carrera armamentista, así como cómo la guerra llevó al derrocamiento del zar y al establecimiento del estado soviético en Rusia.
IHI Certificate - 1 IHI Open School Basic CertificAlyssa Luongo
This certificate recognizes that Alyssa Luongo successfully completed 23.5 hours of online learning covering topics such as improvement capability, patient safety, leadership, person- and family-centered care, triple aim for populations, and quality, cost, and value. The certificate was awarded by the Institute for Healthcare Improvement's IHI Open School for Health Professions.
O documento discute o efeito da cementita globular na resistência mecânica e tenacidade de aços ferríticos com grãos ultrafinos. Foi realizado tratamento termomecânico em aço baixo carbono para produzir grãos ultrafinos e cementita finamente dispersa. Ensaios mecânicos mostraram que o material com grãos ultrafinos teve maior resistência e energia de impacto. Microscopia eletrônica revelou que a cementita atua como barreira ao movimento de discordâncias nos grãos, melhorando as propried
1) O documento discute a influência do tratamento térmico de recozimento na microestrutura de um aço inoxidável austenítico com alto teor de nitrogênio utilizado em implantes ortopédicos.
2) Foram realizados tratamentos térmicos de recozimento em 600, 700, 800 e 900°C para estudar a cinética de precipitação e correlacionar o ciclo térmico com a precipitação na matriz e nos contornos de grão.
3) A caracterização microestrutural revelou transformações de fases, fer
Este documento discute o efeito da precipitação de cementita na formação de contornos de alto ângulo e no refino de grão ferrítico durante o processamento subcrítico de aços. Experimentos de torção a morno foram realizados em aços com 0,16% C e ultrabaixo carbono após tratamentos térmicos. Os resultados mostraram que a precipitação de cementita e a recristalização dinâmica da ferrita contribuem para o refino de grão e formação de contornos de alto ângulo durante a deformação subcrí
This document provides an agenda for a materials science session taking place on August 29, 2005. It lists 18 presentations covering topics in fatigue fracture analysis, fractographic analysis of welded joints, fracture toughness testing, biocompatibility testing of titanium alloys, and microstructural characterization of biomaterials and ceramics. The presentations involve laboratory testing and characterization of materials including metals, polymers, composites, and ceramics for biomedical and engineering applications.
Este documento informa al Dr. Villar que su trabajo titulado "EFFECT OF CEMENTITE PARTICLES IN FORMATION OF HIGH ANGLE BOUNDARIES AND OF ULTRAFINE GRAINS IN LOW CARBON STEEL", con O. Villar da Silva Neto y O Balancin como autores, ha sido aceptado para ser presentado oralmente en el 9no Congreso Interamericano de Microscopia Electrónica en Cusco, Perú del 23 al 28 de septiembre. Más detalles sobre la presentación oral, como la fecha, hora y sala, serán notificados posteriormente.
This document summarizes a study on obtaining ultrafine ferritic grains in a 0.16C steel through subcritical torsion. Samples were austenitized at 1100°C, quenched, and tempered for varying times from 0.25 to 48 hours to evaluate the influence of cementite precipitation on grain refinement. After tempering and reheating to 700°C, samples underwent hot torsion testing. Microstructural analysis found finer and more dispersed carbides in samples with lower tempering times. Precipitate size had little influence on ferritic grain refinement. Ultrafine grains below 2 μm were achieved for all tempering times through strains induced by subcritical hot torsion testing.
The document summarizes a symposium on microanalysis and analytical microscopy of materials. It provides details on the organizers, invited speakers, and oral presentations to be given at the symposium. The symposium will take place from October 10-13, 2004 in Brazil and will include topics such as new applications of electron microscopy in nanotechnology, compositional analysis of interfaces using electron microscopy techniques, and microscopy studies of catalysts and ceramics. Poster sessions will also be held on October 11th and 13th.
El documento presenta una serie de ejercicios relacionados con el cálculo de velocidad, rapidez y distancia en movimientos rectilíneos uniformes. Se explican las fórmulas necesarias para resolverlos y se dan los pasos de cálculo. Luego, se plantean 13 ejercicios resueltos sobre distintos escenarios de movimiento como pelotas, abejas, trenes y automóviles, calculando magnitudes como velocidad, rapidez y tiempo en función de la distancia y el tiempo dados.
El documento habla sobre un slidecast. En pocas palabras, un slidecast es una presentación en formato digital que combina diapositivas con una grabación de audio o video. El slidecast permite al creador grabar su presentación y compartirla con otros de forma dinámica.
The document summarizes analysis of labor data from the Bureau of Labor Statistics for Iowa from 2006-2015. Key points:
- Data was downloaded, cleaned, filtered to only include Iowa data, and concatenated into a single dataset for analysis.
- Occupations were clustered and categorized into 3 groups: Professional, Manual Labor, and Personal Services. Geographical areas were also grouped.
- Analysis found higher salaries in college towns and metro areas for professionals, with salaries exceeding $60k recently. Median incomes were highest for professionals, followed by manual labor, and lowest for personal services statewide.
- Salary distributions were explored, finding the gap between lower and higher salaries growing for most areas and occupations, particularly
O documento apresenta 60 exercícios de combinatória e binômio de Newton envolvendo combinações, permutações e cálculos de possibilidades de agrupamentos de elementos respeitando diferentes restrições. Os exercícios abordam temas como agrupamentos de livros, pessoas, letras do alfabeto, formação de comissões respeitando gênero e profissão, construção de figuras geométricas a partir de pontos e cálculo de diagonais de polígonos e sólidos geométricos regulares.
Brandon Garcia has over 10 years of experience in various fields including information technology, customer service, sales, marketing, and construction crew leadership. He is currently working to obtain 10 IT certifications through My Computer Career. Previously he has held positions such as general manager of a sports bar and bowl, marketing director, pipe fitter crew lead, and sales roles for fitness memberships and telemarketing.
Este documento describe dos grandes conflictos en Europa del siglo XX: las revoluciones rusas de 1905-1917 y la Primera Guerra Mundial de 1914-1918. Explica las causas profundas económicas, políticas y sociales de ambos eventos, incluyendo las rivalidades imperialistas, el nacionalismo y la carrera armamentista, así como cómo la guerra llevó al derrocamiento del zar y al establecimiento del estado soviético en Rusia.
IHI Certificate - 1 IHI Open School Basic CertificAlyssa Luongo
This certificate recognizes that Alyssa Luongo successfully completed 23.5 hours of online learning covering topics such as improvement capability, patient safety, leadership, person- and family-centered care, triple aim for populations, and quality, cost, and value. The certificate was awarded by the Institute for Healthcare Improvement's IHI Open School for Health Professions.
O documento discute o efeito da cementita globular na resistência mecânica e tenacidade de aços ferríticos com grãos ultrafinos. Foi realizado tratamento termomecânico em aço baixo carbono para produzir grãos ultrafinos e cementita finamente dispersa. Ensaios mecânicos mostraram que o material com grãos ultrafinos teve maior resistência e energia de impacto. Microscopia eletrônica revelou que a cementita atua como barreira ao movimento de discordâncias nos grãos, melhorando as propried
1) O documento discute a influência do tratamento térmico de recozimento na microestrutura de um aço inoxidável austenítico com alto teor de nitrogênio utilizado em implantes ortopédicos.
2) Foram realizados tratamentos térmicos de recozimento em 600, 700, 800 e 900°C para estudar a cinética de precipitação e correlacionar o ciclo térmico com a precipitação na matriz e nos contornos de grão.
3) A caracterização microestrutural revelou transformações de fases, fer
Este documento discute o efeito da precipitação de cementita na formação de contornos de alto ângulo e no refino de grão ferrítico durante o processamento subcrítico de aços. Experimentos de torção a morno foram realizados em aços com 0,16% C e ultrabaixo carbono após tratamentos térmicos. Os resultados mostraram que a precipitação de cementita e a recristalização dinâmica da ferrita contribuem para o refino de grão e formação de contornos de alto ângulo durante a deformação subcrí
This document provides an agenda for a materials science session taking place on August 29, 2005. It lists 18 presentations covering topics in fatigue fracture analysis, fractographic analysis of welded joints, fracture toughness testing, biocompatibility testing of titanium alloys, and microstructural characterization of biomaterials and ceramics. The presentations involve laboratory testing and characterization of materials including metals, polymers, composites, and ceramics for biomedical and engineering applications.
Este documento informa al Dr. Villar que su trabajo titulado "EFFECT OF CEMENTITE PARTICLES IN FORMATION OF HIGH ANGLE BOUNDARIES AND OF ULTRAFINE GRAINS IN LOW CARBON STEEL", con O. Villar da Silva Neto y O Balancin como autores, ha sido aceptado para ser presentado oralmente en el 9no Congreso Interamericano de Microscopia Electrónica en Cusco, Perú del 23 al 28 de septiembre. Más detalles sobre la presentación oral, como la fecha, hora y sala, serán notificados posteriormente.
This document summarizes a study on obtaining ultrafine ferritic grains in a 0.16C steel through subcritical torsion. Samples were austenitized at 1100°C, quenched, and tempered for varying times from 0.25 to 48 hours to evaluate the influence of cementite precipitation on grain refinement. After tempering and reheating to 700°C, samples underwent hot torsion testing. Microstructural analysis found finer and more dispersed carbides in samples with lower tempering times. Precipitate size had little influence on ferritic grain refinement. Ultrafine grains below 2 μm were achieved for all tempering times through strains induced by subcritical hot torsion testing.
The document summarizes a symposium on microanalysis and analytical microscopy of materials. It provides details on the organizers, invited speakers, and oral presentations to be given at the symposium. The symposium will take place from October 10-13, 2004 in Brazil and will include topics such as new applications of electron microscopy in nanotechnology, compositional analysis of interfaces using electron microscopy techniques, and microscopy studies of catalysts and ceramics. Poster sessions will also be held on October 11th and 13th.
This document summarizes a study that investigated the effect of cementite particles on ultra-fine ferrite grain growth in low-carbon steel after subcritical aging. Transmission electron microscopy was used to analyze the microstructure. The aging treatment produced an ultra-fine ferrite grain size of 1.0-1.4 micrometers with both fine globular and rod-shaped cementite particles distributed between the grains. During aging, both the ferrite grains and cementite particles coarsened normally via Ostwald ripening. The cementite particles were found to effectively inhibit ferrite grain growth, matching predictions from Rios' grain growth model.
This study investigated grain refinement of ferrite in low-carbon steel through thermomechanical processing near the A1 temperature. Samples underwent spheroidization at 670C followed by torsion straining at 700C, producing ferrite grains less than 2 microns. Both conventional and quenched/strained routes resulted in homogeneous microstructures with fine ferrite grains and cementite precipitates pinning grain boundaries. Increasing strain rate decreased ductility, indicating recrystallization was the dominant refinement mechanism aided by cementite precipitation at boundaries. Sub-critical temperatures were effective for accelerating cementite precipitation and grain refinement.
This document examines the effect of carbon content on grain refinement in C-Mn and interstitial-free (IF) steels deformed via warm working. Four steels with varying carbon contents were strained at 700°C to 2.3. Dynamic recrystallization resulted in a 2 μm ferrite grain size at the surface for all steels. However, microstructures varied between the center regions based on carbon content, from coarse grains in IF steel to martensite and bainite in the highest carbon steel. Increasing carbon decreased ferrite grain size after deformation but also increased strength, while alloying elements aided additional refinement.
The document studied the effect of nitrogen on precipitation in an austenitic stainless steel used in orthopedic implants. It found that high nitrogen content led to precipitation of niobium nitrides in all annealing temperatures due to nitrogen's higher affinity for niobium than chromium. Two types of nitrides, chromium nitride and niobium nitride, were identified along with intermetallic phases Z and χ containing chromium, niobium, and molybdenum. The significant presence of nitrogen and niobium in the steel composition drove precipitation of these phases.
1) O documento estuda o efeito do tratamento térmico de envelhecimento na tenacidade do aço inoxidável austenítico ISO 5832-9 usado como biomaterial.
2) Amostras foram tratadas em temperaturas de 600-900°C por 1-24 horas e suas propriedades mecânicas foram avaliadas por ensaios de dureza e impacto Charpy.
3) O tratamento a 900°C por 1-4 horas proporcionou a maior tenacidade, enquanto a 800°C produziu as condições mais
Este documento descreve um estudo sobre o refinamento da microestrutura de um aço de baixo carbono durante o processamento termo-mecânico a morno. Amostras foram temperadas, revenidas a 700°C por diferentes tempos e deformadas a 700°C. O revenimento levou à precipitação de cementita e o refino ocorreu durante a deformação, resultando em grãos ferríticos ultrafinos independente do tempo de revenimento.
Este documento descreve o estudo do refino de grão ferrítico em um aço baixo carbono submetido a tratamentos termomecânicos. Dois processos foram comparados: esferoidização convencional a 670°C e esferoidização induzida por deformação a 700°C. Ambos levaram à precipitação de partículas finas de cementita e grãos ferríticos menores que 2μm. A deformação mecânica após esferoidização acelerou o refino de grão, enquanto a quantidade de deformação foi mais
1) The document investigates obtaining ultrafine ferrite grains in a low-carbon steel through hot torsion deformation and tempering at sub-critical temperatures.
2) A steel with 0.16% C and 1.34% Mn containing spheroidized cementite was heavily deformed via hot torsion at 685°C and strain rates from 0.1 to 1 s-1.
3) Microstructural analysis found ultrafine ferrite grains less than 2 μm formed, with dispersed spheroidal cementite, indicating dynamic recrystallization during subcritical deformation was responsible for the grain refinement.
Este documento descreve uma pesquisa sobre o refino de grãos em aço baixo carbono através de deformação a quente. A microestrutura inicial consistia de martensita com partículas finas de cementita. Após grandes deformações a quente, observou-se uma microestrutura ferrítica ultrafina com grãos de ~1 μm e partículas de cementita dispersas, indicando refino microestrutural devido à subdivisão de grãos e ancoragem de contornos.
Este documento investiga como a precipitação de cementita durante o processamento termomecânico influencia o refino de grão ferrítico e a formação de contornos de alto ângulo em aços de baixo carbono. Os autores deformaram amostras de dois aços (0,16% C e ultrabaixo carbono) a morno e analisaram a evolução da microestrutura usando microscopia eletrônica. Eles concluíram que a precipitação de cementita e a recristalização dinâmica da ferrita são responsáveis pelo ref
Este documento descreve um estudo sobre a microestrutura do metal de solda do aço ASTM-A36 obtido por soldagem a arco submerso variando o insumo de calor. A microestrutura do metal de solda é afetada pelo insumo de calor utilizado durante a soldagem, com altos insumos de calor promovendo uma maior taxa de resfriamento e alterando os constituintes microestruturais como a ferrita acicular. Amostras foram soldadas variando o insumo de calor de 1,27kJ/mm a 1,
Este documento descreve um estudo sobre o efeito da precipitação de cementita no refino de grão ferrítico durante o processamento subcrítico de um aço baixo carbono. Amostras do aço foram tratadas termicamente para precipitar cementita e então deformadas por torção a quente. Análises microestruturais mostraram que as partículas de cementita auxiliaram no refino de grão e na geração de contornos de alto ângulo durante a deformação.
1. O documento discute o refino de grãos em aços baixo carbono através de processamentos termomecânicos para aumentar simultaneamente a resistência mecânica e a tenacidade.
2. As principais técnicas discutidas são a laminação a morno em múltiplos passes e a deformação plástica severa, porém esta última requer equipamentos especializados que tornam a produção em massa inviável.
3. Os parâmetros-chave para o controle da microestrutura final com grãos ultrafinos
1. FORMATION OF HIGH ANGLE BOUNDARIES AND GRAIN REFINING DURING THE
SUBCRITICAL PROCESSING OF 0,16C STEEL
Silva Neto, O.V. 1,* ; Balancin, O.
1,2
Department of Materials Engineering, Federal University of São Carlos - DEMa/UFSCar, Via
Washington Luiz, Km 235, 13.565-905, São Carlos, SP, Brazil, e-mail: pvillar@iris.ufscar.br
A promising way to enhance, simultaneously, strength and toughness of steel without altering its chemical
composition is promoting the refinement of its microstructure, especially when the average size of common
steels ferritic grain can be reduced to 1 µm [1-4]. Such levels of refinement have been obtained from the
application of large levels of deformation, separately or in a combination sequence of these events [4-6]. The
preferable sites of ferrite nucleation are enhanced, according to the increase of the defects produced during
the deformation. The deformation creates complex fields of obstacles, and then a huge increase in the
activity of the dislocations emerges in the interior of the sub-grains, enhancing the density of dislocations in
order to reach the critical energy for initial nucleation [7-8]. Thus, like the heavy deformation, large strain
rates promote the increase of the defects quantities and of the deformation bands, which contribute to the
occurrence of the dynamic recrystallization and ultrafine ferrite formation [3]. The continuous dynamic
recrystallization refines the microstructure, and the presence of thin dispersed particles possesses the effect
of pinning, anchoring the grains boundaries [4-5]. In this work, we study the grain refinement in low carbon
steel, using samples with thin particles of cementite dispersed in the ferritic matrix submitted to the lukewarm
deformation process. A 0.16C 1.34Mn common steel with dispersion of globular cementite was submitted to
the heavy deformation in the ferritic domain. The initial microstructure was obtained from the formation of
globular cementite through the thermal treatments of quench and tempering. To characterize the
microstructure of deformation, tests with pre-determined interruptions in certain levels of deformation were
carried through. The samples were reheated at 900ºC, they were kept at this temperature for 10 minutes,
and then they were water-quenched. These samples were tempered at 685ºC for 1 hour. Heavy
deformations ( ε = 5 ) were applied through hot torsion tests at 685ºC at equivalent strain rates of 1.0, 0.5 e
-1
0.1 s . They also carried through tests with interruptions after pre-defined deformation amounts – 0, 1, 2, 3,
4 and 5 – in which the samples were water cooled, allowing the study of the microstructural evolution on the
-1
condition of 0.1 s deformation. From these specimens, samples for electronic and optical microscopy
analysis were prepared, with which they measured the average sizes of the grains/sub-grains. The use of the
EBSD (Electron Backscattering Diffraction) technique, accomplished in a Philips microscope of high
resolution, XL30 FEG (30KV) model, enabled the attainment of data related to the misorientation amongst
grains and/or sub-grains. The final microstructure revealed itself recrystallized and composed by ultrafine
grains, with final average size of 1 µm. Three phenomena are more likely to be responsible for the presence
of the ultrafine grains: the process of ferrite dynamic softening (continuous dynamic recrystallization), the
rotation and break of the initial microstructure boundaries, and the cementite particles, which interfered with
the process of rotation of the sub-grains, and the formation and grains growth.
Acknowledgements:
The authors acknowledge the Brazilian Research Funding Agencies CAPES, CNPq and FAPESP for
the financial support.
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