Neste trabalho foram estudadas soldas TIG (Tungsten Inert Gas) nos aços inoxidáveis 304 e 316, e no aço carbono 1020. As alterações das microestruturas foram investigadas por microscopias óptica (MO) e eletrônica de varredura (MEV), enquanto que a corrosão destas regiões foi estudada por análises de polarização potenciodinâmica. Um sistema miniaturizado de análise corrosão, denominado sensor pontual de corrosão (SPC), foi utilizado com o objetivo de analisar a estreita região dos cordões de solda, estudando assim a influência da corrente de solda na corrosão desta região nos aços inoxidáveis 304 e 316. Os resultados mostraram que a alteração da estrutura cristalina na solda tornou esta região menos susceptível à corrosão que o material base, e o aumento da corrente de solda intensificou ainda mais este efeito, pela formação de estruturas mais compactas. No caso do aço carbono 1020 (mais susceptível à corrosão), o estudo da corrosão de sua solda foi feito utilizando técnicas eletroquímicas globais (potencial de circuito aberto, PCA, e espectroscopia de impedância eletroquímica, EIE) e técnicas de corrosão localizadas (espectroscopia de impedância eletroquímica localizada, EIEL, e técnica do eletrodo vibratório de varredura, TEVV). Para proteção contra a corrosão do aço inoxidável e suas soldas, foi utilizado um revestimento de polianilina (PAni) na forma de base esmeraldina; análises de polarização potenciodinâmica mostraram a eficiência deste revestimento protetor. Para o aço carbono 1020, devido à sua maior facilidade de oxidação, foi sintetizado um revestimento protetor a base de PAni e nanotubos de TiO2 (PAni/n-TiO2). As variáveis estudadas na síntese do polímero foram: temperatura de síntese, meio reacional, grau de dopagem do polímero (condutor ou isolante) e número de camadas. Os polímeros e compósitos foram caracterizados por espectroscopias nas regiões do ultravioleta-visível (UV-vis) e infravermelho (IV), MEV e espectroscopia de energia dispersiva de raios-X (EDX). Os aços recobertos com os filmes foram analisados por MO e MEV, EDX, e por ensaios eletroquímicos de polarização potenciodinâmica, PCA e resistência de polarização, além de ensaio de corrosão acelerada em câmara de névoa salina. As melhores condições encontradas foi para o revestimento de PAni/n-TiO2 desdopado (base esmeraldina) sintetizado a 25°C em meio de H2SO4, e com 3 camadas; o n-TiO2 apresentou um efeito de aumento da aderência do filme ao substrato metálico. / In this work TIG (Tungsten Inert Gas) welds have been studied in the 304 and 316 stainless steels, and in the 1020 carbon steel. The changes in the microstructure were investigated by optical microscope (OM) and scanning electronic microscope (SEM), and the corrosion behavior in these zones were studied by potentiodynamic polarization analysis. A miniaturized corrosion analysis device, named corrosion punctual sensor, has been used to analyze the close weld bead, researching for the influence of the weld current in the corrosion process in this zone of the 304 and 316 stainless steels. The results showed that the change in the crystalline structure of the weld zone became this region less susceptible to corrosion process than their base material, and the increase in the weld current intensified this effect, by the formation of more compact structures. In the case of the 1020 carbon steel (more susceptible to corrosion processes), the corrosion in its weld zone was researched by global (like open potential circuit, OCP, and electrochemical impedance spectroscopy, EIS) and localized (like localized electrochemical impedance spectroscopy, LEIS, and scanning vibrating electrode technique, SVET) electrochemical techniques. For protecting stainless steels and their weld zones against corrosion processes, a polyaniline (PAni) coating in the emeraldine base form was used; potentiodynamic polarization analysis showed the efficiency of this protective coating. For the 1020 carbon steel, due to its mayor oxidation susceptibly, a protective coating of PAni and TiO2 nanotubes (PAni/n-TiO2) was synthesized. The variables researched were: synthesis temperature, reaction medium, degree of doping of the polymer (conductor or insulator) and number of layers. The polymers and composites were characterized by ultraviolet visible (UV-vis) and infrared spectroscopies, SEM and Energy Dispersive X-Ray Spectroscopy (EDX). The coated steels were analyzed by OM, MEV and EDX spectroscopies, and by potentiodynamic polarization, OCP and polarization resistance electrochemical measurements, besides accelerate corrosion tests in a salt spray chamber. The best conditions found for the dedoped PAni/n-TiO2 coatings (emeraldine base) were: temperature of synthesis of 25°C, H2SO4 as reaction medium, and with 3 layers; n-TiO2 has presented an effect of increasing the adherence of the coating with the steel.

A demanda da indústria automobilística por aços de boa estampabilidade, para aplicação em peças expostas motivou o desenvolvimento de várias especificações de aços livres de intersticiais (IF) na Companhia Siderúrgica Nacional. A especificação de aço \"IFTi\", pertencente ao grupo de aços para estampagem extra profunda especial (CSN EEPIF), com limite de resistência < 380 MPa está, dentre todos os graus de aço processados nas linhas de laminação a frio, entre os que apresentam a maior porcentagem de desvio por marca de rebarba e outros problemas relacionados ao corte. A geração de uma rebarba com altura excessiva está relacionada a um corte de má qualidade. Durante o processo de laminação a frio essa rebarba pode aumentar ainda mais de tamanho, se desprender, marcar os cilindros de trabalho e conseqüentemente aumentar os custos de produção por desvios e troca precoce de cilindros. Nas linhas de decapagem, a tesoura de pontas final é o equipamento responsável por separar as bobinas soldadas no início do processo e definir a característica de corte das pontas e caudas das mesmas, através de corte por guilhotinamento. Visando aumentar a qualidade, produtividade, diminuir as perdas durante o processo e atender às exigências dos clientes internos e externos, foi necessário desenvolver o processo de corte por guilhotina do aço IF nas tesouras de pontas final das Linhas de Decapagem Contínua 3 e 4 da CSN. Através da simulação de corte em laboratório, usando-se a mesma velocidade de avanço e ângulo de inclinação do equipamento de campo, avaliou-se a relação entre o ajuste de folga entre navalhas e o comportamento força x deslocamento no cisalhamento. Além disso, através da análise por microscopia eletrônica de varredura (MEV) foi possível observar o efeito dos varios ajustes de folga na superfície de fratura, identificando as regiões de corte citadas na literatura e sua relação com as características microestruturais e com as propriedades do material. Constatou-se que a tensão cisalhante durante o corte diminuía a medida em que a folga aumentava de forma linear para uma faixa de folga ajustada entre 6 e 12%t em amostras de aço IF-Ti com 1,5mm de espessura. Nas micrografias feitas em MEV, observou-se que as interfaces entre penetração e fratura ficaram irregulares em todos os casos, sendo uma região intermediária, com aspecto misto entre as regiões de penetração e fratura foi relacionado ao desencontro das frentes de trincas principalmente devido ao grande ângulo de fratura. Tanto os perfis de corte quanto as superfícies de fratura mostraram que a fração da região de corte diminuía com o aumento da folga, até certo ponto, quando a partir da mudança do comportamento da tensão cisalhante, voltava a aumentar. Pode-se verificar também, que a fração da região de deformação aumentava à medida que folgas maiores eram testadas e os valores atingidos eram muito superiores as deformações esperadas para as respectivas características do tipo de corte indicado pelas regiões de penetração e fratura. Os melhores resultados de corte foram obtidos na regulagem de folga entre 4 e 8%t, com rebarbas inferiores a 1,5%t, menores frações da região de deformação e interface corte/fratura mais regulares do que nas demais faixas de folga. / The automotive industry\'s demand for high formability steels for use in exposed body panels motivated the development of several interstitial free (IF) steels specifications at Companhia Siderurgica Nacional. The \"IF-Ti\" steel specification belongs to the special deep drawing steels group (CSN EEP-IF), with yield strength <380 MPa, and among all grades of steel processed in the cold rolling lines is the one with the highest amount of deviation by burr marks and other problems related to shearing. The generation of an excessive burr height is related to a poor cut quality. During the cold rolling process the burr can increase in size, break off, mark the work rolls and therefore increase production costs per deviation and early exchange of cylinders. In the pickling lines, the exit shear is the device responsible for separating the coils welded at the beginning of the process and to define the cutting head and tail characteristics, either through guillotine cutting. Aiming to increase quality, productivity, reduce losses during the process and meet the requirements of internal and external customers, it was necessary to develop the guillotine cutting process of the IF steel sheet extremities (head and tail) in the exit shears of Continuous Pickling Lines #3 and #4 at CSN. Through the cutting simulation in the laboratory, using the same forward speed and rake angle adopted in the field equipment, was evaluated the relationship between the adjustment of clearance between blades and the behavior shear force versus displacement. In addition, through the analysis by scanning electron microscopy (SEM) it was possible to observe the effect of several settings on the fracture surface, identifying the different regions cited in the literature and its relation to the microstructural characteristics and to the material properties. It was found that the shear stress during cutting reduced as the gap increased linearly to a range between 6 and 12%t in samples of IF-Ti steel with 1.5 mm thick. In the micrographs taken by SEM, it was observed that the interfaces between burnished and fracture were irregular in all cases, where an intermediate depth, with mixed aspect between the burnished and fracture depths was related to mismatch of crack fronts mainly due to the large fracture angle. Both cut profiles as the fracture surfaces showed that the burnished depth decreased with increasing the gap to some extent, since from the behavior change of shear stress, it started to increase. It was also possible to verify that the fraction of therollover depth increased as larger gaps were tested and the values achieved were much higher than expected for the rollover characteristics of the respective type of cut indicated by the burnished and fracture depths. The best cutting results were obtained for clearance adjustment between 4 and 8%, resulting in burrs below 1.5%t, smaller rollover depth and more regular burnished/fracture interface than in other clearance ranges tested.

O presente trabalho teve por objetivo realizar ensaios de desgaste abrasivo em juntas soldadas pelo processo MAG, em dois aços estruturais de alta resistência e baixa liga utilizados no transporte ferroviário de minério, os quais apresentavam diferentes propriedades mecânicas. No aço de menor resistência (Aço A) foram utilizados os metais de adição AWS ER70S-G (Aço A-70) e AWS ER80S-G (Aço A-80), enquanto no aço de maior resistência (Aço B) os metais de adição AWS ER80S-G (Aço B-80) e AWS ER110S-G (Aço B-110). Os conjuntos soldados foram caracterizados quanto às suas microestruturas, dureza e resistência ao desgaste abrasivo em ensaios de degaste roda de borracha e ensaios de desgaste por deslizamento a seco e com adição de um meio corrosivo (NaCl 0,05M, água arti cial ). Os resultados obtidos a partir dos ensaios de desgaste roda de borracha mostraram que para o Aço A a junta soldada do Aço A-70 apresentou melhor resistência ao desgaste, enquanto para o Aço B a maior resistência ao desgaste foi obtida na junta soldada Aço B-110. Dos resultados dos ensaios de desgaste por deslizamento a seco, as zona afetada pelo calor de grãos grosseiros (ZAC-GG) foram as regiões que apresentaram a maior resistência ao desgaste. Das condições soldadas no Aço A, o metal base (MB) apresentou a menor resistência ao desgaste, entre os metais de solda (MS), o MS do Aço A-80 apresentou a maior resistência ao desgaste. No Aço B, o MS do Aço B-80 apresentou a menor resistência ao desgaste, e o MS do Aço B-110 apresentou a resistência ao desgaste similar ao MB. Foi observado um maior desgaste para as amostras que foram submetidas ao ensaio de desgaste por deslizamento com solução, comparativamente às amostras submetidas aos ensaios a seco, o que, de acordo com a literatura, está associado ao efeito sinérgico entre corrosão e desgaste. / The present work had the objective perform abrasive wear tests on GMA welded joints in two high strength low alloy structural steels used in rail transport of ore, which presented di erent mechanical properties. The AWS ER70S-G and AWS ER80S-G wires were used in the lower strength steel (Steel A), whereas the AWS ER80S-G and AWS ER110S-G wires were used in the higher strength steel (Steel B). The welded joints were characterized in terms of their microstructures, hardness and abrasive wear resistance in dry sand/rubber wheel tests and sliding wear tests dry and with a corrosive medium (0.05M NaCl, arti cial water ). The results obtained from the dry sand/rubber wheel tests showed that for Steel A the welded joint with the wire AWS ER70S-G showed better wear resistance, while for Steel B the highest wear resistance was obtained with the AWS ER110S-G wire. From the results of dry sliding wear tests, the coarse grained heat a ected zone were the regions that presented the highest wear resistance. In Steel A, the base metal (BM) showed the least resistance, and between the weld metals (WM), the WM Steel A-80 showed the highest wear resistance. In Steel B, WM Steels B-80 showed the least wear resistance, while the WM Steels B-110 showed the wear resistance similar to BM. It was observed a higher wear for the samples that were submitted to the sliding wear test with solution, compared to the samples submitted to the dry wear test, which, according to the literature, is associated with the synergic e ect between corrosion and wear.

Em determinadas rotas de manufatura de componentes automotivos, principalmente de produtos do segmento rodoviário pesado, são muito comuns processos de desempeno a quente, assim como outros procedimentos como arqueamento e alinhamento de longarinas. O presente trabalho tem por objetivo traçar os principais impactos destes processos sobre os materiais ASTM A570 GR36-C e o aço de alta resistência e baixa liga norma DIN EN 10149 S700MC em uma rota de fabricação de produtos automotivos com interferência de um procedimento a quente. Esses materiais, quando submetidos a determinados ciclos térmicos para alinhamento a quente, através do aquecimento de algumas regiões pontuais e do posterior resfriamento ao ar calmo têm suas propriedades mecânicas alteradas. Para investigar estas modificações, foram reproduzidas as condições do processo atual para mapeamento de dados de temperatura para os subsequentes ensaios de laboratório. Comparando as amostras submetidas ao ciclo térmico, com as produzidas com a mesma matéria prima sem aquecimento, pode-se verificar o impacto causado pelo processo de alinhamento a quente utilizado sobre as propriedades mecânicas do material. Os resultados mostram que o aço ASTM A570 GR36-C não tem suas propriedades alteradas a ponto de inviabilizar o uso do material. Para o aço DIN EN 10149 S700MC as alterações são expressivas em todos os ciclos térmicos realizados. Com isso, ocorrem modificações na microestrutura pelo tratamento térmico ocasionando a diminuição de algumas propriedades mecânicas importantes, como tensão de escoamento, microdureza e limite de resistência à fadiga. Essas últimas variáveis foram correlacionadas e mostraram o mesmo comportamento. / In certain manufacturing routes of automotive components, especially of heavy road segment products are very common straightening processes hot, as well as other procedures such as bending and alignment of rails. This paper aims to draw the main impacts of these processes on ASTM A570 GR36-C materials and high strength low alloy steel DIN EN 10149 S700MC on a route manufacturing of automotive products with interference from a hot procedure. These materials, when subjected to certain thermal cycles to hot alignment by heating of certain individual regions and the subsequent cooling the still air have changed their mechanical properties. In order to investigate this, they were reproduced the conditions of the current process for temperature mapping data for subsequent laboratory tests. Comparing the samples subjected to thermal cycling with produced with the same raw material unheated, one can ascertain the impact caused by hot alignment process used on the mechanical properties of the material. The results show that the steel ASTM A570 GR36-C does not have its properties changed as to make the use of the material. To DIN EN 10149 S700MC Steel changes are significant in all thermal cycles performed. Thus, changes occur in the microstructure by heat treatment causing a reduction of some important mechanical properties such as yield strength, hardness and fatigue strength limit. The latter variables were correlated and showed the same behavior.

The Quenching and Partitioning (Q&P) heat treatment has been proposed in the early 2000s to produce cold-rolled sheets combining high-strength and formability for the automotive market. Q&P consists, first, of an interrupted quench between the martensite-start temperature (Ms) and the martensite-finish temperature (Mf) from intercritical annealing or full austenitization in order to form controlled fractions of martensite. This is followed by a partitioning step in order to stabilize the untransformed austenite through carbon enrichment. In order to maximize the carbon transfer from martensite to austenite, the use of specific alloying elements and the design of appropriate Q&P parameters are required to eliminate or minimize competing phenomena such as carbide formation and austenite decomposition. The final quenched and partitioned microstructure, using full austenitization, ideally consists of carbon-depleted lath martensite and significant fractions of retained austenite providing an improved combination of strength and ductility. Hence, the transformation of retained austenite upon straining at room temperature (TRIP effect) provides supplementary work-hardening and eventually improves the ductility. In the present work, Quenching and Partitioning (Q & P) heat treatments were carried out in a quench dilatometeron a 0.2 wt% carbon steel. The microstructure evolution of the Q & P steels was characterized usingdilatometry, SEM, EBSD and XRD. The martensitic transformation profile was analyzed in order to estimate thefraction of martensite formed at a given temperature below the martensite start temperature Ms. Q & P wasshown to be an effective way to stabilize retained austenite at room temperature. However, the measuredaustenite fractions after Q & P treatments showed significant differences when compared to the calculated valuesconsidering ideal partitioning conditions. Indeed, the measured austenite fractions were found to be less sensitiveto the quench temperature and were never larger than the ideal predicted maximum fraction. Competitivereactions such as austenite decomposition into bainite and carbide precipitation were found to occur in thepresent work.Furthermore, a broad range of mechanical properties was obtained when varying the quenching temperaturesand partitioning times. The direct contributions between Q & P microstructural constituents -such as retainedaustenite as well as tempered/fresh martensite- and resulting mechanical properties were scrutinized. This wascritically discussed and compared to quenching and austempering (QAT) which is a more conventional processingroute of stabilizing retained austenite at room temperature. Finally, Q & P steels were shown to exhibit aninteresting balance between strength and ductility. The achievement of this interesting combination of mechanicalproperties was reached for much shorter processing times compared to QAT steels. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This Miniature mechanical testing study is concerned with the use of miniature specimens to identify the mechanical properties of stainless steel Type 304, sensitized Type 304 and SA516 Grade 70 carbon steel as a viable replacement for the standard sized mechanical testing. The study aims at obtaining suitable specimen geometry and tensile testing proce- dure for miniature mechanical testing whose mechanical properties are comparable to that of conventional specimens of ASTM A370-10 of the same steel. All specimens are at and the gauge length cross section will be varied to obtain suitable geometry. The miniature tensile testing results are further validated by using Monte Carlo Method (MCM) for uncertainty estimation in order to know the probability distribution of mechanical properties. Miniature specimens with a cross section of 3 mm2 and 12 mm gauge length are found to produce equiva- lent mechanical properties as tested from standard-sized specimens. If a reasonable agreement is received, it will provide us with a very useful tool to evaluate mechanical properties of de- graded materials, which cannot be removed from service for standard testing, for repair and service life evaluation.

The ductility of Q&P 1180 steel was studied with regard to retained austenite transformation under different strain paths. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Stretching experiments were also performed using limiting dome height (LDH) tooling, where specimens were strained in both biaxial and plane strain tension. The experiments were done incrementally, for each strain path, and the retained austenite at each level of strain was measured using electron backscatter diffraction (EBSD). Retained austenite levels in the uniaxial tension case dropped from an initial measured level of about 8% to about 2% during an initial strain increment of 0.02, but then stabilized as the specimen was strained to 0.1. In the plane strain and biaxial tension cases retained austenite also dropped significantly during an initial strain increment of about 0.04, but then continued to decrease as the specimens were strained to failure. Biaxial tension, in particular, was the most effective strain path for transforming retained austenite to martensite, resulting in a final volume fraction of 0.3% at an effective strain of 0.3. Retained austenite in the plane-strain tension case dropped at a faster rate than in the biaxial tension case, but finished at about 1% at a strain of 0.1. The greatest limit strains were seen in the biaxial tension case, which may be partly explained by the more effective conversion of retained austenite than was seen in the uniaxial tension case.

Ce travail est dédié à la quantification de l'effet du champ magnétique sur les transformations de phases dans les alliages à base de fer et en particulier dans les aciers. Le Fer pur, les alliages Fe-xNi, et les aciers au carbone faiblement alliés Fe-xC-Mn et Fe-C-Mn-xSi sont étudiés afin d'explorer une large gamme de transformations et de microstructures. Un dilatomètre haute-température et une balance magnétique pour la mesure de susceptibilité magnétique sont utilisés pour la caractérisation des transformations diffusive dans un champ magnétique allant jusqu'à 16T. Un troisième outil d'élaboration sous champ magnétique a été entièrement développé au cours de ce travail et permet pour la première fois une étape de trempe des matériaux à l'eau, à l'huile ou par gaz pulsé. Les températures de transformation hors-équilibre mesurées jusqu'à 16T dans une large gamme d'alliages sont augmentées par l'application d'un champ magnétique. Ces variations dans la température de transformation sont modélisées par un calcul thermodynamique basée sur une analogie avec l'effet d'une pression hydrostatique sur les équilibres de phases. Les microstructures d'aciers faiblement alliées obtenue par trempe sont largement modifiées par l'application du champ magnétique : d'une structure composée de martensite et de bainite sans l'application d'un champ magnétique, l'austénite se décompose en un mélange de ferrite allotriomorphe et de ferrite de Widmanstätten dans une matrice de bainite et de martensite en présence d'un champ magnétique. Ce travail apporte la preuve que le champ magnétique est devenu un paramètre prometteur en métallurgie physique. Associé aux techniques existantes, son utilisation peut conduire à l'obtention de matériaux aux propriétés innovantes.

<p>Many engineering components reach a finite fatigue life well above 10⁹load cycles. Some examples of such components are found in airplanes, automobiles or high speed trains. For some materials the fatigue failures have lately been found to occur well after 10⁷ load cycles, namely in the Very High Cycle Fatigue (VHCF) range. This finding contradicted the established concept of fatigue limit for these materials, which postulates that having sustained 10⁷ load cycles the material is capable of enduring an infinite number of cycles provided that the service conditions are unchanged. With the development of modern ultrasonic fatigue testing equipment it became possible to experimentally establish VHCF behaviour of various materials. For most of them the existence of the fatigue limit at 10⁷ load cycles has been proved wrong and their fatigue strength continues to decrease with increasing number of load cycles.</p><p> </p><p>One important group of materials used for the production of high performance components subjected to the VHCF is tool steels. This study explores the VHCF phenomenon using experimental data of ultrasonic fatigue testing of some tool steel grades. The causes and mechanisms of VHCF failures are investigated by means of high resolution scanning electron microscopy, and in relation to the existing theories of fatigue crack initiation and growth. The main type of VHCF origins in steels are slag inclusions.</p><p>However, other microstructural defects may also initiate fatigue failure. A particular attention is paid to the fatigue crack initiation, as it has been shown that in the VHCF range crack formation consumes the majority of the total fatigue life. Understanding the driving forces for the fatigue crack initiation is a key to improve properties of components used for very long service lives. Finite element modelling of VHCF testing was added as an additional perspective to the study by enabling calculation of local stresses at the fatigue initiating defects.</p><p> </p><p> </p>

Martensite is considered to be the backbone of the high strength of many commercial steels. Martensite is formed by a rapid diffusionless phase transformation, which has been the subject of extensive research studies for more than a century. Despite such extensive studies, martensitic transformation is still considered to be intriguing due to its complex nature. Phase-field method, a computational technique used to simulate phase transformations, could be an aid in understanding the transformation. Moreover, due to the growing interest in the field of “Integrated computational materials engineering (ICME)”, the possibilities to couple the phase-field method with other computational techniques need to be explored. In the present work a three dimensional elastoplastic phase-field model, based on the works of Khachaturyan et al. and Yamanaka et al., is developed to study the athermal and the stress-assisted martensitic transformations occurring in single crystal and polycrystalline steels. The material parameters corresponding to the carbon steels and stainless steels are considered as input data for the simulations. The input data for the simulations is acquired from computational as well as from experimental works. Thus an attempt is made to create a multi-length scale model by coupling the ab-initio method, phase-field method, CALPHAD method, as well as experimental works. The model is used to simulate the microstructure evolution as well as to study various physical concepts associated with the martensitic transformation. The simulation results depict several experimentally observed aspects associated with the martensitic transformation, such as twinned microstructure and autocatalysis. The results indicate that plastic deformation and autocatalysis play a significant role in the martensitic microstructure evolution. The results indicate that the phase-field simulations can be used as tools to study some of the physical concepts associated with martensitic transformation, e.g. embryo potency, driving forces, plastic deformation as well as some aspects of crystallography. The results obtained are in agreement with the experimental results. The effect of stress-states on the stress-assisted martensitic microstructure evolution is studied by performing different simulations under different loading conditions. The results indicate that the microstructure is significantly affected by the loading conditions. The simulations are also used to study several important aspects, such as TRIP effect and Magee effect. The model is also used to predict some of the practically important parameters such as Ms temperature as well as the volume fraction of martensite formed. The results also indicate that it is feasible to build physically based multi-length scale model to study the martensitic transformation. Finally, it is concluded that the phase-field method can be used as a qualitative aid in understanding the complex, yet intriguing, martensitic transformations. / QC 20120525 / Hero-m