No description available.

Powder metallurgy is a branch of metal forming technology where metal powders are used to manufacture parts and components. It is a flexible and economical technique for manufacturing complicated shapes. This present work focuses on press and sinter technology and forms a part of Höganäs’s efforts of modelling hardenability through quenching. It aims to reduce the number of experimental trials for optimising heat treatment. Hardenability is a measure of how much martensite can be formed during heat treatment, thereby making steels hard, tough and impart strength. The presence of alloying elements like carbon, manganese, chromium, molybdenum, and nickel affects the hardenability of the steel and improves performance like fatigue strength and corrosion resistance. These elements influence the critical cooling rate necessary to form martensite during heat treatment. Component geometry also influences hardenability. Depending on the surface area available to cool, and volume of component, cooling rates may locally be different thereby resulting in an inhomogeneous structure. The work focuses particularly on two grades of powders manufactured by Höganäs AB - Astaloy® CrA and Astaloy® CrS which are evaluated for their hardenability. The aim of this work is to take cooling conditions observed in the actual furnace, use them to predict the amount of martensite present and the martensite start temperature and then compare it with experimental results thereby linking experiment to simulations. For the experimental part, dilatometry was used. Quenching data is obtained from the furnace along with heat capacity of the component and are used as input in Abaqus, which gives us the cooling rates for the component in the furnace. This data is then utilised as an input to dilatometry, where the samples are representative of sections of component. After dilatometry, vital information like martensite start temperature is recorded and metallography is performed, where phase fraction is obtained. Hardness measurements are also performed to verify the phases present. Simulation tools like JMatPro and Thermo-Calc are employed to obtain data for correlation. An extensive study on the difference between them are also studied and presented. The data from simulation and actual experiment is compared and, Ms evaluated from JMatPro and Thermo-Calc for CrA shows a deviation of 12°C. For CrS samples, a higher deviation is observed, with JMatPro showing deviation of 44°C and Thermo-Calc, 52°C in respect to the measured values. For CrA, we observe a fully martensitic structure for the higher carbon samples, including ones alloyed with Ni. For samples with lower carbon, metallographic investigation results in an unclear picture as to if the structure observed is bainite or martensite. CrS samples are mostly martensitic with some bainite present. CrS samples alloyed with Ni and Cu show the least amount of bainite present. The phase fractions predicted by JMatPro show good agreement with results from metallography. Data from microhardness confirms the presence of phases present. Samples with low carbon are softest but show a great improvement in hardness when alloyed. Overall, simulations and actual experimental values are seen to be in good agreement, thereby establishing a strong foundation for future work, where actual components can be evaluated. Quenching conditions observed in the furnace are validated through this work. / Pulvermetallurgi är en gren av metallformningsteknik där metallpulver används för att tillverka delar och komponenter. Det är en flexibel och ekonomisk teknik för att tillverka komplicerade former. Detta nuvarande arbete fokuserar på press- och sinterteknik och är en del av Höganäs arbete med att modellera härdbarhet genom härdning. Det syftar till att minska antalet experimentella försök för att optimera värmebehandlingen. Härdbarhet är ett mått på hur mycket martensit som kan bildas vid värmebehandling, vilket gör stålen hårda, sega och ger styrka. Närvaron av legeringselement som kol, mangan, krom, molybden och nickel påverkar stålets härdbarhet och förbättrar prestanda som utmattningshållfasthet och korrosionsbeständighet. Dessa element påverkar den kritiska kylningshastighet som krävs för att bilda martensit under värmebehandling. Komponentgeometrin påverkar också härdbarheten. Beroende på den yta som är tillgänglig för kylning och volymen av komponenten, kan kylningshastigheterna lokalt vara olika, vilket resulterar i en inhomogen struktur. Arbetet fokuserar särskilt på två kvaliteter av pulver tillverkade av Höganäs AB - Astaloy® CrA och Astaloy® CrS som utvärderas för sin härdbarhet. Syftet med detta arbete är att ta kylförhållanden som observerats i den faktiska ugnen, använda dem för att förutsäga mängden närvarande martensit och martensitens starttemperatur och sedan jämföra den med experimentella resultat och därigenom koppla experiment till simuleringar. För den experimentella delen användes dilatometry. Släckningsdata erhålls från ugnen tillsammans med värmekapaciteten hos komponenten och används som indata i Abaqus, vilket ger oss kylhastigheten för komponenten i ugnen. Dessa data används sedan som indata till dilatometry, där proverna är representativa för sektioner av komponenten. Efter dilatometri registreras viktig information som martensitstarttemperatur och metallografi utförs, där fasfraktion erhålls. Hårdhetsmätningar utförs också för att verifiera de närvarande faserna. Simuleringsverktyg som JMatPro och Thermo-Calc används för att få data för korrelation. En omfattande studie om skillnaden mellan dem studeras och presenteras också. Data från simulering och faktiska experiment jämförs och Ms utvärderade från JMatPro och Thermo-Calc för CrA visar en avvikelse på 12°C. För CrS-prover observeras en högre avvikelse, där JMatPro visar en avvikelse på 44°C och Thermo-Calc, 52°C i förhållande till de uppmätta värdena. För CrA observerar vi en helt martensitisk struktur för de högre kolproverna, inklusive de som legerats med Ni. För prover med lägre kolhalt resulterar metallografisk undersökning i en oklar bild av om den observerade strukturen är bainit eller martensit. CrS-prover är mestadels martensitiska med viss bainit närvarande. CrS-prover legerade med Ni och Cu visar den minsta mängden bainit som finns närvarande. Fasfraktionerna som förutspåtts av JMatPro visar god överensstämmelse med resultaten från metallografi. Data från mikrohårdhet bekräftar närvaron av faser. Prover med låg kolhalt är mjukast men visar en stor förbättring i hårdhet när de är legerade. Sammantaget bedöms simuleringar och faktiska experimentella värden stämma överens, vilket skapar en stark grund för framtida arbete, där faktiska komponenter kan utvärderas. Släckningsförhållanden som observerats i ugnen valideras genom detta arbete.

Bead-on-plate laser welds were made on an industrially produced DP780 steel to determine the effect of normalized welding heat input on the microstructure and mechanical properties within the weld fusion zone (FZ) and heat affected zone (HAZ) with reference to the base material (BM) mechanical properties. Normalized welding heat input was calculated using an established model from the literature utilizing measurements from the weld cross-section microstructures along with known materials properties. Microhardness profiles and optical microscopy were employed to evaluate materials properties and microstructural changes across the various microstructural zones of each weld. The mechanical properties of the welds were evaluated globally through standard ASTM tensile specimens as well as through a series of specialized mechanical testing sample geometries which examined the properties of individual microstructural zones. These specialized sample geometries included non-standard uniaxial and plain strain tension where effective stress and effective strains were used to compare the mechanical properties across samples. It was determined that there was a good correlation between ASTM standard samples and the specialized sample geometries employed in this study and that the UTS and YS values obtained in both cases were comparable. Sigmoidal decay behaviour was observed in the UTS and YS with increasing heat input for both the FZ and HAZ of all welds. It was found that welds with heat inputs greater than 60 J/mm2 had both a UTS and YS which were significantly depressed in the FZ and HAZ when compared to the base material values. Conversely, welds with heat inputs below 36.3 J/mm2 were found to have a UTS and YS in both the FZ and HAZ microstructural zones which were above the values determined for the BM. When global weld properties were tested, it was found that welds with a heat input greater than 60.0 J/mm2 failed within the HAZ while welds with heat inputs below 36.3 J/mm2 failed within the BM. It has been shown that there is a significant correlation between the heat inputs of laser welded DP steels and both the mechanical properties and microstructural features of the various microstructural zones as well as the location of failure during weld tensile testing. It has also been demonstrated that the mechanical properties of weld microstructural zones can be qualitatively evaluated using specialized tensile testing geometries. / Thesis / Master of Applied Science (MASc)

The martensite structure is the most important microstructure in tool steel due to its high hardness. However, a lack of ductility is the major drawback. In order to improve the ductility and still maintaining a suitable hardness a tempering process is needed. The tempering process will cause recovery and recrystallization in the matrix, and moreover carbides will precipitate. The specific carbides have different characteristics and thus the type of carbide formed during tempering is very important for the properties of the steel. The simulation software (TC-Prisma) is interesting because it can predict type, size, and amount of carbides. The present study was carried out to investigate both the microstructure, hardness evolution of martensite and precipitation which occurred in Fe-C-Cr steel with different compositions, tempered at 700oC. The experimental results were compared with simulation results. Micro-Vickers hardness test with a load of 100 g was used and the hardness value dropped 40% and 60% in low carbon alloy and high carbon alloy steels, respectively. The significant drop occurred during the first 30 seconds of tempering due to recovery of the matrix. Hardness values slightly decreased and then stabilized during continued tempering. The microstructure of martensite and the morphology of carbides at different tempering times were examined by scanning and transmission electron microscopy in order to study the precipitation of carbides from the nucleation and growth to coarsening. There are three types of carbides which precipitated in the Fe-C-Cr specimens: M7C3, cementite and M3C2 depending on the composition. Fe-0.16C-4.05Cr contained M7C3, Fe-0.95C-1.065Cr contained cementite and M3C2 and Fe-014C-0.983Cr and Fe-0.88C-4.12Cr contained M7C3 and cementite. M7C3 has a faceted shape and precipitates referentially at grain boundaries. On the other hand, cementite has an elongated shape and precipitated mainly at grain boundaries but also intragranulary. M3C2 has a rounded shape and was seen only in very small amounts, and seemed to precipitate at random sites. The trend of carbide growth in experiments is consistent with the simulations using TC-Prisma, but more work is needed to enable quantitative comparisons.

No description available.

Powder metallurgy (PM) steel is produced by near net shape manufacturing, which is used to fabricate alloy steels for many purposes. Designing new powder metal steels that can form a significant fraction of martensite relies on hardenability calculations developed for wrought steels. These proven tools are built upon assumptions for wrought steels that do not hold true for PM steels. One assumption is that the alloying elements are homogenized throughout the material. In admixed powder blends that are industrially sintered this is not the case. Using prealloyed powder is a solution to this issue, yet it places restrictions on alloy design and compressibility. There are tools available to computationally optimize diffusion problems, yet the complexity during the sintering of PM steel is such that a robust model has yet been produced. It is intuitive that with smaller particles of Fe sintering time can be reduced. A direct experimental investigation linking Fe-powders’ sizes and hardenability on Fe-C-Cr-Mn-Mo-Ni PM steel was subject to microstructure analysis and mechanical properties (Jominy test) for comparative analysis. Another assumption that is made for wrought steel is a consistent density of 7.87g/cm3. This is not the case for PM steel as the press and sinter method produces pores, decreasing the density. This directly affects the thermal conductivity and phase transformation of the steel. In an effort to understand how these differences affect Grossmann’s predictions of hardenability, a direct experimental investigation linking the density to hardenability was launched on prealloyed FL-4605 and FL-4605+2%Cu. Specifically the Jominy test was completed on a range of densities, as well as compared to software predictions. The chemical variations in admixed and sintered PM steel produce a unique system where one TTT diagram cannot predict the entire final microstructure. PM steel such as this is observed in industry, and can be created through incorporating larger Fe-particles such that less alloying constituents have a chance to fully alloy these regions. Since the large particles will not have the chance to be alloyed, they will not have the ability to form martensite. Since the regions between large particles will be alloyed, martensite will form, creating a hard matrix surrounding softer particles. This structure is characteristic of a metal matrix composite (MMC), and therefore should be treated as such. There are methods of MMC design that involve numerical methods of predicting strength and toughness. These methods, along with experimental data (tensile and Charpy testing) of Fe-C-Cr-Mn-Mo-Ni PM steels with ranging volume fractions of pearlitic inclusions were compared. / Thesis / Master of Applied Science (MASc)

Ni-Mn-X (X = Ga, Sn, In, Sb)-based Heusler alloys are an emerging class of multifunctional materials that demonstrate high-stroke actuation induced by magnetic field, caloric cooling, and thermomagnetic energy harvesting from low-grade waste heat. These capabilities are enabled by a reversible martensitic phase transformation, which is a first-order diffusionless transformation from the high-temperature cubic austenite phase to the low-temperature martensite phase with a reduced crystal symmetry. As a result, a complex hierarchical arrangement of twin boundaries occurs within the martensite microstructure that influences the multifunctional properties of these alloys. In addition, optimum properties occur mostly in the single crystalline state, which makes epitaxial films an ideal candidate for integrating these alloys in microsystems. Nevertheless, the success of this integration relies on understanding the effects of miniaturization on the martensitic transformation and microstructure, which remain largely unexplored in epitaxial films. Hence, the present work investigates size-effects in the martensite microstructure of epitaxially grown Ni-Mn-Ga-based films. For film microfabrication, the suitability of conventional etching techniques is studied, leading to the development of a two-step Ar ion beam etching process. Additionally, a process for fabricating freestanding patterns is developed, leveraging the conventional silicon microtechnology. The size-effect investigation of fabricated patterns attached to the substrate reveals a surface martensite microstructure identical to continuous films, with no noticeable changes in features. This is attributed to the rigid constraint imposed by the substrate on the patterns, which hinders any anticipated changes in the microstructure. In contrast, a fundamentally unique martensite microstructure manifests in freestanding films, revealed from the film surface and cross-sections. Transmission electron microscopy is used to examine the features and assemble a comprehensive 3D picture of their arrangement within the martensite microstructure. To explain the origin, a concept based on invariant line constraint is introduced, which allows to quantitatively derive the key microstructural features. The concept also underlines the role of finite film thickness and the lack of substrate constraint in causing a microstructure arrangement different from that of bulk single crystals and constrained epitaxial films. Furthermore, the unique magnetic microstructure of the freestanding film is analyzed by magnetic force microscopy, revealing a peculiar checkerboard-like pattern. The features in the magnetic microstructure are elucidated using a phenomenological model of magnetic domain arrangement, stemming from the magnetostructural coupling in these alloys. To further investigate size-effects, the surface martensite microstructure is analyzed in freestanding films of varying thicknesses and freestanding patterns varying in lateral size, aspect ratio, and orientation. The features in the martensite microstructure scale linearly with film thickness due to the internal twinning geometry observed in the film cross-section. In contrast, the microstructure is not influenced by any changes in pattern characteristics. Hence, this study identifies film thickness as the decisive size parameter influencing the martensite microstructure of freestanding films and patterns.:1 Introduction 1 1.1 Research Objectives and Motivation . . . . . . . . . . . . . . . . . . . . . . . 2 2 Fundamental Concepts and State of the Art 5 2.1 Ferroic Properties of Ni-Mn-Ga-based Alloys . . . . . . . . . . . . . . . . . . 5 2.2 Multifunctionality of Ni-Mn-based Alloys . . . . . . . . . . . . . . . . . . . . 8 2.3 Epitaxial Ni-Mn-Ga-based Films . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 Factors Influencing Film Microstructure . . . . . . . . . . . . . . . . . . . . 18 2.5 Size-Effects in Ni-Mn-Ga-based Alloys . . . . . . . . . . . . . . . . . . . . . 20 3 Experimental Methods 28 3.1 Film Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.2 Microfabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.3 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4 Microfabrication Approach for Ni-Mn-Ga-based Films 35 4.1 Wet Chemical etching of Films . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2 Reactive Ion Etching of Films . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.3 Ion Beam Etching of Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4 Fabrication of Freestanding Patterns . . . . . . . . . . . . . . . . . . . . . . 44 5 Size-Effects in Constrained Ni-Mn-Ga-based Patterns 46 5.1 Martensite Microstructure of Continuous Film . . . . . . . . . . . . . . . . . 46 5.2 Martensite Microstructure of Constrained Patterns . . . . . . . . . . . . . . 48 5.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 6 Multiferroic Microstructure Created from Invariant Line Constraint in Freestanding Films 52 6.1 Martensite Microstructure: From Cross-sections to 3D Picture . . . . . . . . 52 6.2 Line Constraint Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 6.3 Checkerboard Magnetic Microstructure . . . . . . . . . . . . . . . . . . . . . 63 7 Size-Effects in Freestanding Ni-Mn-Ga-based Films and Patterns 68 7.1 Microstructure Evolution with Film Thickness . . . . . . . . . . . . . . . . . 68 7.2 Microstructure in Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 7.3 Martensitic Transformation in Pattern . . . . . . . . . . . . . . . . . . . . . 73 7.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 8 Summary and Outlook 75 Appendix A 79 Bibliography 86 List of Abbreviations 96 List of Scientific Works 97 Acknowledgement 99

Les aciers TWIP se déforment par maclage et par glissement de dislocations, avec pour conséquence de forts taux d’écrouissage. Les mécanismes de déformation sont contrôlés par l’énergie de faute d’empilement (EFE). Un modèle de prévision de l’EFE et une régression de TNéel (transition antiferro/paramagnétique) de l’austénite sont proposés pour les systèmes FeMnXC (X = Cu, Cr, Al, Si et Ti). Les nuances FeMnCuC étudiées ont une EFE plus faible que la nuance de référence Fe22Mn0,6C. La formation de martensite [epsilon]?se substitue au maclage, sans dégradation des caractéristiques mécaniques en traction. La contrainte d'écoulement diminue avec la teneur en carbone et la formation de martensite [alpha]' aux plus basses EFE réduit l'allongement à rupture. La substitution d'une partie du manganèse par du cuivre permet un gain de 20% sur le module d'Young à température ambiante, en abaissant TNéel en dessous de 0ºC. La précipitation intragranulaire de carbures de vanadium augmente la limite d’élasticité mais n’influence pas le taux d’écrouissage. Aucune interaction entre précipités et macles n'a été observée en microscopie. Les calculs de cohérence et les mesures au MET montrent que les carbures ont une relation d'orientation avec l'austénite et sont semi-cohérents avec une faible cohérence résiduelle. Les contraintes induites ne semblent pas suffisantes pour piéger de grandes quantités d'hydrogène. Les alliages FeMnC + TiC présentent un fort durcissement par effet composite en début de déformation, tandis que l'écrouissage par effet TWIP n'est pas modifié par la présence des particules TiC. Cependant, le clivage des précipités primaires de grande taille réduit l'allongement à rupture / TWIP steels deformation occurs by twinning and by dislocations gliding which leads to high a strain hardening. The deformation mechanisms are controlled by the stacking fault energy (SFE). A model for the prediction of the SFE and a law for TNéel (antiferro to paramagnetic transition) for austenite are proposed in FeMnXC systems (X = Cu, Cr, Al, Si et Ti). The studied FeMnCuC grades have a lower SFE than the Fe22Mn0,6C reference. The formation of [epsilon]-martensite replaces twinning without any deterioration of the mechanical properties. The flow stress decreases with the carbon content and the formation of [alpha]'-martensite at the lowest SFEs reduces the elongation to fracture. Substituting a part of the manganese content by copper leads to a 20% increase of the Young's Modulus at room temperature by decreasing TNéel below 0ºC. The precipitation of intragranular vanadium carbide increases the yield stress but does not influence the strain hardening rate. No interaction between precipitates and twins has been observed by microscopy. The coherency calculations and the TEM observations show that the carbides have an orientation relation with the austenite and are semi-coherent with a low residual coherency. The resulting stresses do not seem to be high enough to trap large quantities of hydrogen. The FeMnC + TiC alloys exhibit a strong hardening by composite effect at the beginning of deformation, while the strain hardening due to TWIP effect is not modified by the presence of the TiC particles. Meanwhile, cleavage occurs in the largest primary precipitates, which reduces the elongation to fracture

Nos últimos anos, devido ao elevado preço do níquel, uma nova série de aços inoxidáveis austeníticos com um menor teor de níquel foi criada. A essa nova série foi dado o nome de série 200. Dentre os aços dessa classe, o AISI 201 tem sido utilizado em aplicações onde a elevada resistência à corrosão não é tão necessária. Neste trabalho de Mestrado investigou-se a formação e a reversão da martensita induzida por deformação em um aço inoxidável austenítico AISI 201 laminado a frio em 20, 40 e 60% de redução em espessura. Das chapas laminadas foram retiradas amostras que foram recozidas em várias temperaturas (200-800oC) por 1 hora. Amostras do material laminado em 60% de redução em espessura também foram recozidas por várias temperaturas (200-800oC) e por vários tempos (5-180min). Com isso, avaliou-se a evolução microestrutural do material durante a laminação frio e durante o recozimento por meio de medidas de microdureza Vickers, microscopias óptica, eletrônica de varredura e eletrônica de transmissão, difração de elétrons retroespalhados, difração de raios X e medidas de magnetização. Além disso, foram realizados cálculos termodinâmicos para a previsão da formação de fases nesse material. Constatou-se que o material de partida não era completamente austenítico, possuindo uma pequena fração de ferrita ? residual em sua microestrutura. Com relação às medidas de magnetização, observou-se que a fração de fase ferromagnética (martensita) aumenta com o aumento da deformação, aumentando a magnetização de saturação (Ms) do material. Para pequenas deformações (20% de redução em espessura) houve a ocorrência de um pico no valor de campo coercivo do material (Hc). Com o aumento da deformação (40 e 60%) os valores de Hc diminuíram. Com relação à reversão da martensita induzida por deformação durante os recozimentos, observou-se que ela ocorre na faixa de temperatura de 500-700oC para o material laminado em 60% de redução em espessura. O comportamento do material nesse estudo corrobora o que tem sido reportado na literatura para os aços da série 300. Entretanto, pouco tem sido publicado com relação às propriedades magnéticas do aço inoxidável austenítico AISI 201, principalmente com relação ao campo coercivo. Neste trabalho também foram realizadas medidas de magnetização durante o recozimento das amostras (condição in situ). Os parâmetros obtidos desses experimentos in situ foram comparados com aqueles obtidos para as amostras recozidas isotermicamente. / In the last years, since nickel price increased, another series of austenitic stainless steel with less amount of nickel has emerged: the series 200. The AISI 201 stainless steel has been used where intermediated corrosion resistance is needed. In this work, the formation of strain-induced martensite and its reversion in an AISI 201 austenitic stainless steel were studied. The material was characterized in terms of microstructure and then cold rolled up to 20, 40 and 60% of thickness reduction. For all degree of reduction, samples were annealed at several temperatures (200-800oC) for 1 hour. Additional samples taken from the 60% cold-rolled material were also annealed at several temperatures (200-800oC) for several times (5-180minutes). The microstructural evolution during cold rolling and annealing was evaluated using microhardness Vikers testing, light optical microscopy, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, X-Ray diffraction and magnetization measurements. Phase predictions were also performed using software Thermo-calc©. It was observed that the as-received material was not fully austenitic. It has a small fraction of ?-ferrite within its matrix. The amount of ferromagnetic phase (martensite) increases with increasing deformation. For small deformation (20%), there is a peak in the coercive field of the material (Hc). As deformation increases, Hc values decrease. It was also observed that the martensite reversion takes place at 500-700oC. The behavior of the material is in accordance with what has been reported in the literature for the 300 series. However, only few works have been reported concerning AISI 201 stainless steel and its magnetic properties. In this work, magnetic measurements were also carried out during annealing (in situ condition). The obtained parameters from the in situ magnetic measurements were compared to those ones obtained from the isothermally annealed samples.

Objetivo principal desta dissertação foi verificar os efeitos da temperatura de laminação na formação de martensita induzida por deformação e na sua posterior reversão da martensita para austenita no aço inoxidável austenítico AISI 304L. O estudo foi predominantemente microestrutural e para análise e caracterização foram utilizadas as técnicas de microscopia óptica, microscopia eletrônica de varredura, difração de raios X, medidas de dureza Vickers e medidas de fases ferromagnéticas por ferritoscopia. As amostras foram inicialmente solubilizadas a 1100 ºC por uma hora, visando a dissolução de uma pequena quantidade residual de ferrita encontrada nas amostras na condição como recebida, depois laminadas em diferentes temperaturas, determinando-se curvas de endurecimento por deformação e de formação de martensita induzida por deformação em função do grau de deformação. Em seguida, foram realizados pré-recozimentos a 600 ºC, favorecendo apenas a reversão da martensita para austenita, de maneira que não ocorresse a recristalização. A quantidade e a temperatura de deformação apresentaram forte influência na quantidade de martensita formada, no endurecimento por deformação e na cinética de amolecimento durante o recozimento. Os pré-tratamentos realizados a 600 ºC causaram acentuada reversão da martensita, algum amolecimento e pequeno efeito no tamanho de grão recristalizado durante o posterior recozimento a 600 ºC. / The main objective of the present dissertation was to verify the effects of the rolling temperature on the formation of strain induced martensite and in its subsequent martensite reversion to austenite in a AISI 304L stainless steel. The study was predominantly microstructural and, for the analysis and characterization, several techniques have been used, namely optical microscopy, scanning electron microscopy, X-ray diffraction, Vickers hardness measurements and magnetic phase measurements, using the ferritoscope. The samples were initially solution annealed at 1100 ºC for one hour, aiming at the dissolution of a small quantity of the residual -ferrite found in the samples in the as-received condition; then rolling was performed at different temperatures, evaluating strain hardening and the strain induced martensite as a function of strain. Following, pre-annealing treatments at 600 ºC have been performed, favoring only the martensite to austenite reversion, in a way that no recrystallization would occur. Strain and temperature had a strong influence on the amount of formed martensite, on the strain hardening and on the softening kinetics during annealing. The pre-annealing treatments at 600 ºC caused an accentuated effect on the martensite reversion, some softening and a small effect on the recrystallized grain size during the subsequent annealing at 600 ºC.