This thesis focuses on the role of interfacial strain in heterostructures to modify the magnetism of thin ferromagnetic films due to the inverse magnetostrictive effect, defined as the change of magnetization produced in ferromagnetic materials by an external stress. Thus, the magnetic control can be obtained without applying an external field by using heterostructures composed of a non-magnetic layer characterized by a temperature-driven structural phase transition coupled to a ferromagnetic layer. In such heterostructures, the magnetization of the ferromagnetic layer is modified through changes in the stress field at the interface when the structural phase transition in the non-magnetic layer (actuator) is carried out. In this work, we used NiTi shape memory alloy as the actuator to modify the magnetic behavior of ferromagnetic films through the magneto-elastic coupling in novel NiTi/Ni and NiTi/Co heterostructures. NiTi, when near its equiatomic composition, is a shape memory alloy that undergoes a reversible structural phase transition with temperature, providing stress on the ferromagnetic film. We chose this alloy because NiTi exhibits a large recovery stress with transition temperatures above room temperature for Ti-rich NiTi films, which is of interest for technological applications of the heterostructures. Since the right microstructure of NiTi is important to observe structural phase transition and it defines the characteristic of the transition, an extensive review on previous research on NiTi is detailed in this thesis. Thus, to ensure large stress during the NiTi structural transition with temperature, the NiTi alloy must be near its equiatomic composition with a thickness above 800 nm. Both characteristics were confirmed by Rutherford Backscattering analyses. The crystal structure and its transition with temperature were studied by X-ray diffraction measurements. In-plane magnetization and hysteresis measurements with temperature, performed on a superconducting quantum interference device (SQUID) magnetometer, prove the magneto-elastic coupling that was observed as an enhancement in the magnetic moment of the ferromagnetic layer. Such enhancement becomes the feature of magneto-elastic coupling in these novel NiTi/ferromagnetic heterostructures. / Esta tese estuda o papel da tensão interfacial em filmes heterogêneos na modificação do magnetismo de camadas ferromagnéticas finas por meio do efeito magnetoestritivo inverso, definido como a mudança de magnetização produzida em materiais ferromagnéticos por um estresse externo. Tecnologicamente, isto visa ter um grau de controle magnético do material sem a aplicação de um campo externo, usando heteroestruturas compostas por uma camada não magnética caracterizada por uma transição de fase estrutural acionada pela temperatura, acoplada a uma camada ferromagnética. Em tais heteroestruturas, a magnetização da camada ferromagnética é modificada através de alterações no campo de tensão na interface quando a transição de fase estrutural na camada não magnética (atuador) é realizada. Assim, utilizamos a liga com memória de forma NiTi como atuador, para modificar o comportamento magnético de filmes ferromagnéticos através do acoplamento magnetoelástico em novas heteroestruturas de NiTi/Ni e NiTi/Co. O NiTi, quando próximo à sua composição equiatômica, é uma liga com memória de forma que sofre uma transição de fase estrutural reversível com a temperatura, proporcionando tensão no filme ferromagnético. Escolhemos esta liga porque o NiTi apresenta uma grande tensão de recuperação com temperaturas de transição acima da temperatura ambiente, para filmes de NiTi ricos em Ti, o que é de interesse para aplicações tecnológicas das heteroestruturas. A microestrutura do NiTi é fundamental para favorecer a transição de fase estrutural e definir as suas características. Assim, uma extensa revisão de pesquisas anteriores sobre NiTi é detalhada nesta tese. Para garantir um grande estresse durante a transição estrutural do NiTi com a temperatura, o filme de NiTi deve estar próximo de sua composição equiatômica e ter espessura acima de 800 nm. Ambas as características foram confirmadas pelas análises de espectroscopia de retroespalhamento Rutherford. A estrutura cristalina e sua transição com a temperatura foram estudadas por medidas de difração de raios X. Medidas de magnetização e histerese em função da temperatura, com campo aplicado no plano dos filmes, realizadas em um magnetômetro SQUID, comprovaram a existência do acoplamento magnetoelástico, o qual se manifestou através de variações no momento magnético da camada ferromagnética. Essas mudanças de magnetização, observadas principalmente na heteroestrutura com Ni, torna-se a característica principal do acoplamento magnetoelástico nesses novos materiais.

Matériaux incontournables des matériaux fonctionnels, les alliages à mémoire de forme(AMF) peuvent présenter de très larges déformations réversibles. La Transformation de Phase Martensitique (TPM), ayant lieu lorsqu’il est soumis à une action mécanique ou thermique, lui confère des caractéristiques particulières. Le comportement thermomécanique des AMF est à présent bien maîtrisé. Cependant la connaissance de leur comportement `a la rupture reste un enjeu majeur pour leur dimensionnement dans le cadre de leur industrialisation pérenne. Ces travaux de recherche se sont attachés `a la connaissance, la description et la quantification du phénomène de localisation en pointe de fissure liée à la TPM induite sous contrainte, au travers du développement d’un modèle prédictif et de sa corrélation expérimentale par mesures de champs simultanées lors d’essais de rupture sur des éprouvettes fissurées de NiTi. Deux modèles analytiques basés sur la mécanique linéaire de la rupture, intégrant le caractère dissymétrique du comportement des AMF en traction/compression, ont été développés pour la prédiction des zones de transformation au voisinage de la pointe de fissure en tenant compte des différents modes de rupture ( élémentaires et mixtes I+II) et du rayon de courbure en pointe de fissure. Un banc de caractérisation par mesures simultanées de champs cinématiques par corrélation d’images (DIC) et thermique par thermographie infrarouge a été développé pour cartographier les champs expérimentaux d’essais de rupture en mode I sur des éprouvettes pré-fissurées. Cette bonne corrélation des modèles analytiques ouvre de nombreuses perspectives concernant l’analyse du couplage thermo mécanique associé à la TPM en pointe de fissure, l’enrichissement des modèles analytiques initiaux, et la confrontation avec les résultats expérimentaux pour des modes de rupture plus complexes (II et mixte I+II). / Major player among functional materials, Shape Memory Alloys (SMA) may undergo verylarge reversible strain. SMA exhibit a Martensitic Phase Transformation (MPT) when they aresubmitted to mechanical or thermal actions, and that gives them some specific characteristics.The thermomechanical behavior of SMA is now well controlled. However, the knowledge of theSMA fracture behavior is a major challenge for their design and sizing for their sustainableindustrialization. This research project has focused on the understanding, describing and quantifyingof the phenomenon of localization at the crack tip due to stress-induced MPT. The study includestwo main aspects: the development of an analytical model and its experimental correlation bysimultaneous field’s measurements during tests on cracked NiTi specimens. Two analytical modelsbased on the linear fracture mechanics and those introduce the asymmetrical nature of the SMAbehavior in tension/compression, were developed for the prediction of transformation zones in thevicinity of the crack tip, taking into account the fracture mode (elementary and mixed ones)and the radii of curvature of the crack tip. A testbench with the measurement of simultaneouskinematic field with Digital Image Correlation (DIC) and thermal field with infrared thermographywas designed for mapping the experimental fields during fracture tests in mode I on pre-crackedspecimen. This good correlation of analytical models opens up many perspectives on the analysisof thermomechanical coupling associated with the MPT at the crack tip, the enrichment of the initialanalytical models, and comparison with experimental results for more complex failure modes (II andmixed I+II).

Cíle této práce jsou: (i) vyhodnocení vlivu Y2O3 kelímku na kontaminaci indukčně tavené NiTi slitiny obohacené niklem, (ii) optimalizace podmínek, při kterých jsou tavby uskutečněny a (iii) získání nových DSC a 3D AP dat o vlivu vodíkové atmosféry na martenzitickou transformaci a na strukturu NiTi slitin obohacené niklem s tvarovou pamětí. Byly provedeny následující experimenty: – Pět taveb bylo navrženo a provedeno tak, aby byla snížena maximální tavící teplota. – Pět přetaveb bylo uskutečněno při teplotě 1500 C s dobou výdrže 2, 10 a 20 minut a při teplotách 1450 C a 1550 C s 20 minutovou dobou výdrže. Experiment byl navržen tak, aby byl vyšetřen vliv tavící teploty a doby výdrže na obsah kyslíku pocházejícího z kelímku Y2O3 v tavenině. – Tepelné zpracování NiTi slitiny obohacené niklem v režimu I (žíhání) a v režimu II (kombinace žíhání se stárnutím) pod atmosférou vodíku, směsi vodíku s héliem a pod referenční atmosférou čistého hélia. Získané výsledky jsou: – Navržené tavící postupy vedou ke snížení maximální tavící teploty a to z 1800 C na 1400 C. Přesto toto velké snížení maximální tavící teploty nevedlo k významnému poklesu obsahu kyslíku. – Během přetavby uskutečněné při teplotě 1500 C s dobou výdrže 2 minuty se obsah kyslíku navýšil o trojnásobek jeho počáteční hodnoty a příliš se nelišil od obsahu kyslíku naměřeného ve slitině, která byla přetavena při stejné teplotě s dobou výdrže 10 minut. K nárustu o čtyřnásobek počáteční hodnoty obsahu kyslíku došlo u přetavby vedené na teplotě 1450 C po dobu 20 minut a hodnota obsahu kyslíku se příliš nelišila od hodnoty naměřené ve slitině přetavené při teplotě 1550 C se stejnou dobou výdrže. – S rostoucím parciálním tlakem vodíku dochází k potlačení jednokrokové martenzitické transformace. Významný pokles výšky DSC píku nastává při parciálním tlaku 100 mbar. 3D AP analýza odhalila, že nedochází k žádné lokální změně koncentrace a nebo pozic niklových a titanových atomů ve vzorku, který byl žíhán v režimu I ve vodíku. Bylo objeveno, že vodík tvoří stabilní intersticiální tuhý roztok v NiTi B2 mřížce, kde vytváří systém nanodomén s obsahem vodíku vyšší než 10 at%.

No description available.

Previous work done at Cal Poly has shown that thin-film nickel-titanium (NiTi) can be easily sputtered onto silicon wafers and annealed to create a crystallized shape memory alloy (SMA) film. Initial work on creating devices yielded cantilevers that were highly warped due to thin-film stress created during the sputtering process. The objective of this work was to create a thin-film NiTi SMA device that could be better characterized. A membrane was selected due to the simplicity of fabrication and testing which would also oppose the thin-film stress due to the increase in attachment points to the substrate. Silicon wafers were etched through the majority of the thickness (~75%) creating square etch pits of varying sizes varying from 1294 µm to 4394 µm. The wafers were then sputtered with an approximate NiTi film of 5 µm followed by a thin chromium film. The chromium film would act as a diffusion barrier and prevent oxygen from diffusing into the NiTi and reacting with the titanium and forming titanium dioxide. These wafers were then annealed in a custom built vacuum annealing chamber at 550 °C for 1 hour with a pressure around 77 kPa. The chromium was then etched away followed by the remaining silicon. This left a thin membrane of shape memory NiTi which was packaged in order for characterization. The devices were glued to an aluminum substrate using polydimethylsiloxane (PDMS) and sealed with a small Tygon tube leading to the sealed chamber. This packaged device was then able to be pressurized using a nitrogen tank and the resulting NiTi membrane deflection was measured using a profilometer. Due to the differences in elastic moduli of the room temperature phase (martensite) and the high temperature phase (austenite) a difference of deflection was expected. The austenite finish (Af) temperature of bulk NiTi films was found to be around 60 °C so the devices were tested at both room temperature and at 60 °C. After testing seven separate devices of varying sizes, a regression model was used to analyze the final data. It was found that pressure, membrane size and theoretical versus actual deflection all affected the maximum deflection, but temperature did not. Higher pressures and larger membranes led to higher deflections as membrane deflection models from fundamental principles indicated. Some devices showed inferior performance when compared to the model due to incomplete silicon etching which caused lower deflection due to the much higher modulus of the remaining silicon. Thickness could also limit the amount of deflection measured with a thicker film leading to less deflection, but this is likely not the case due to the high uniformity of the sputtering system. Other devices showed superior performance over the model most likely due to either local delamination or lateral silicon etching. Both these would create a membrane that was larger than expected leading to a higher deflection. Unforutnaly, differential scanning calorimetry (DSC) analysis showed no shape memory behavior on a test wafer which was anneald at 550 ˚C for 1 hour. A design of experiments was conducted in order to find a heat treatment that would anneal the NiTi film and ensure that shape memory behavior could be obtained. An annealing at 650 °C for 1 hour showed a sharper and clearer Af phase transformation at around the target temperature of 60 °C. Annealing a full wafer at this temperature and time also showed that no delamination would occur which has also been linked to nonideal behavior of the NiTi membranes which has also been linked to meaningful behavior of the NiTi membranes.

La transformation martensitique thermoélastique apparaissant dans les alliages à mémoire de forme (AMF) de type Nickel-Titane (NiTi) est un mécanisme de déformation conférant à ces matériaux des propriétés remarquables de plus en plus utilisées. Les forts phénomènes de localisation des déformations lors d'essais de traction superélastique remettent en cause l'utilisation de cet essai pour bâtir des lois de comportement, alors que d'autres essais comme la torsion et le cisaillement apparaissent comme plus homogènes.<br />Ce travail de thèse est dédié à l'analyse des mécanismes de déformation des AMF NiTi. Les comportements homogènes et localisés ont été étudiés en fonction des géométries d'échantillons, des types de sollicitations et des conditions d'essais. L'originalité de cette étude est d'utiliser deux méthodes de mesures de champs : (i) la corrélation d'images afin d'obtenir les champs cinématiques et d'observer les localisations de déformation ; (ii) la thermographie infrarouge pour mesurer les champs de température et analyser les phénomènes de changement de phase. Afin d'utiliser ces techniques simultanément, des outils de recalage spatial et temporel des données ainsi que des techniques d'estimation de sources de chaleur ont été développés. Lors d'essais superélastiques, cette étude a permis d'une part de mettre en évidence la présence de changement(s) de phase homogène en début de charge et de décharge, d'autre part de caractériser de manière quantitative les différentes morphologies de localisation. Les outils développés sont une première tentative pour disposer, à l'issue de ce travail, d'une DSC locale sous chargements mécaniques.

Ce travail est consacré à l'élaboration et l'analyse de comportement thermomécanique d'un composite constitué d'une matrice en résine époxyde renforcée par des fils en alliage à mémoire de forme (AMF). Le fil, en NiTi écroui a été soumis à trois traitements thermiques afin d'obtenir des caractéristiques de transformation différentes. Trois types d'échantillons, nommés : pull-out, traction simple et éprouvettes à géométrie complexe ont été réalisés. Les composites ont été fabriqués par moulage suivi d'une une cuisson et d'une post-cuisson. Les tests ont été effectués à trois températures (20, 80 et 90 ° C) et à vitesse de chargement constante. Des échantillons mono-filaments ont été réalisés et soumis à un essai d'arrachement afin d'étudier l'effet de la transformation martensitique sur l'initiation et la propagation de la décohésion. D'après les observations in situ, la décohésion commence à partir du point d'entré des fils et continue vers la fin de la longueur noyée. Il a été constaté expérimentalement que, la transformation martensitique dans le fil diminue la vitesse de propagation de la décohésion interfaciale et augmente la résistance de l'interface au cisellement. Le comportement mécanique de la matrice, l'effet de la température d'essai et de la fraction volumique de fil ont été déterminés en utilisant le test de traction simple. Les essais ont été conduits à trois températures. Il est constaté que la transformation martensitique se produisant dans le fil influe de manière significative le comportement mécanique des échantillons composites. L'augmentation de la contrainte de transformation améliore la résistance du composite à la traction. Ceci est réalisé soit en augmentant la température d'essai ou en faisant un traitement thermique à une température plus basse. Il est proposé que dans le composite la transformation se produit simultanément en plusieurs points. On observe alors, une intermittence de zones décollées et non décollées. Dans ce travail, les échantillons à géométrie complexe ont été conçus et fabriqués afin d'estimer les propriétés élastiques du matériau composite dans deux directions (parallèle et transverse à l'axe du fil). Des spécimens avec un mouchetis aléatoire ont été soumis à un chargement simple. Les champs hétérogènes de déplacement/ de déformation générés grâce à la géométrie complexe des échantillons composites ont été mesurées. Une méthode inverse a été développée et les paramètres du matériau ont été identifiés. Les résultats ont ensuite été comparés aux résultats obtenus par la méthode de Mori-Tanaka. Le champ de déformation obtenu numériquement, à partir des paramètres identifiés a été comparé à ceux obtenus expérimentalement. Une bonne corrélation a été trouvée dans les deux cas.

Desde que fueron descubiertas en el principio de los años sesenta, las aleaciones con memoria de forma de NiTi han suscitado un interés creciente. Hoy en día, estos materiales se emplean extensivamente en el campo biomédico. No obstante, su utilización exige tomar precauciones especiales, por los problemas de alergia y/o toxicidad que pueden ser provocados por la liberación de los iones Ni que contiene este material. Por este motivo, se han desarrollado una gran cantidad de tratamientos superficiales, con el fin de disminuir la concentración superficial de Ni y, consecuentemente, minimizar su liberación al medio exterior. Sin embargo, no existe todavía ningún tratamiento de superficie estándar que sea satisfactorio para a la vez reducir la cantidad superficial de Ni, mejorar la resistencia a la corrosión del material, y reducir su citotoxicidad y/o trombogenecidad.El objetivo de esta tesis doctoral es la obtención y la caracterización de un nuevo tratamiento de superficie de las aleaciones de NiTi para aplicaciones biomédicas. Se estudiaron también las correlaciones entre las características físico-químicas y topográficas de las superficies de NiTi estudiadas y la respuesta proteica y celular in vitro. Se optimizó un nuevo tratamiento de oxidación térmica (OT) que forma un óxido de titanio, TiO2 en la superficie de las aleaciones de NiTi, casi libre de Ni. Este tratamiento no altera de manera sensible las propiedades de memoria de forma de estos materiales. El tratamiento OT incrementa la rugosidad de las superficies de NiTi y homogeniza las diferencias topográficas que existen entre las distintas aleaciones sin tratamiento. Además, las superficies tratadas con OT tienen características energéticas y electrostáticas superficiales de mayor similitud con las del Ti puro, en comparación con las superficies sin tratamiento. Por otra parte, el óxido formado con OT permite (i) reducir de manera significativa la liberación de los iones Ni al medio, (ii) reducir la incorporación de iones Ni en las células osteoblásticas cultivadas en contacto con el material NiTi, y (iii) mejorar la resistencia a la corrosión del NiTi. Asimismo, las aleaciones de fase austenítica y tratadas con OT no son sensibles, en cuanto a su resistencia a la corrosión, a los daños superficiales que se pueden producir en el óxido. Sin embargo, en el caso de las aleaciones de fase martensítica tratadas con OT, la resistencia a la corrosión disminuye cuando se raya el óxido. En cuanto a la adsorción proteica, el tratamiento OT incrementa, tanto la adsorción de albúmina como de fibronectina, comparado con las superficies sin tratamiento. Se observa, además, que mientras que la albúmina se adsorbe de forma proporcional a la componente polar de la energía superficial del NiTi, la adsorción de fibronectina está gobernada por otras propiedades superficiales adicionales.Por último, los resultados de los cultivos celulares in vitro demuestran que las aleaciones de NiTi, sin tratamiento y tratadas con OT, no son citotóxicas. Los osteoblastos cultivados sobre las superficies OT presentan, además, un grado de diferenciación mayor, en las condiciones del estudio, comparado con las superficies sin tratamiento. En conclusión, se propone el nuevo tratamiento de oxidación obtenido como candidato para garantizar el buen comportamiento del NiTi en las aplicaciones biomédicas. La capa de óxido formada minimiza los riesgos de alergias y toxicidad provocados por los iones Ni. Además, las superficies tratadas con este nuevo tratamiento de oxidación pueden mejorar la respuesta biológica del material a largo plazo, puesto que tienen propiedades físico-químicas similares a las del Ti puro. / Since their discovery, at the beginning of the 1960's, the interest for NiTi Shape Memory Alloys has constantly increased. Nowadays, these materials are extensively used in the biomedical field. However, special care must be taken because of the problems of allergy and toxicity that can be associated with the release of Ni ions contained in these materials. A great variety of surface treatments was developed to decrease Ni surface concentration, and consequently, minimize its release to the exterior medium. However, there is no satisfactory standard surface treatment that improves corrosion resistance and reduces cytotoxicity and/or thrombogenicity of NiTi material. The aim of this PhD thesis is to obtain and to characterise a new oxidation treatment of NiTi alloys for biomedical applications. Correlations between physicochemical and topographical properties of NiTi surfaces and, protein and in vitro cell response have also been studied. A new oxidation treatment (OT) has been optimized to form a titanium oxide (TiO2), almost Nifree, on NiTi alloys surfaces. This treatment does not significantly alter the shape memory properties of these materials. The OT treatment increases the roughness of NiTi surfaces and homogenizes the topographical differences that were present on the untreated surfaces studied. Moreover, the surfaces treated with OT have surface energy and electrostatic characteristics more similar to pure Ti than untreated surfaces.Additionally, the oxide formed by OT allows to(i) significantly decrease Ni ions release to the exterior medium, (ii) decrease Ni ions incorporation into osteoblastic cells cultured on NiTi surfaces, and (iii) improve the corrosion resistance of NiTi. Austenitic alloys treated with OT are not sensitive, regarding to corrosion resistance, to scratches produced on their surface oxide. In the case of martensitic alloys, corrosion resistance decreases when their oxide are scratched. Regarding protein adsorption, the OT treatment also increases albumin adsorption, as well as fibronectin one, compared to untreated surfaces. While albumin adsorption is proportional to the polar component of surface energy of NiTi, fibronectin adsorption is governed by other additional surface properties.Finally, the in vitro cell culture results show that NiTi alloys, untreated and treated with OT, are not cytotoxic. Moreover, the osteoblasts cultured on OT surfaces show a better differentiation, in the study conditions, than untreated surfaces. As a conclusion, the new oxidation treatment obtained is proposed as a good candidate to guaranty an adequate behaviour of NiTi materials for biomedical applications. The oxide layer formed minimizes the risks of allergy and toxicity caused by Ni ions. Moreover, because of their similar surface physicochemical properties to pure Ti, the surfaces treated with this new oxidation treatment can improve the long-term biological response of NiTi alloys.

Shape memory alloys (SMA) offer several advantages over traditional electro-mechanical devices, including: smooth, silent, clean operation; linear actuation; high power/weight ratio; scalability; and reduced part counts. These unique characteristics make them an attractive option when developing actuators, particularly at the meso- and micro-scales. However, SMAs do not typically display cyclic actuation and, therefore, require some reset force or bias mechanism in order to achieve this behaviour. Additionally, the micro-assembly of SMA material with a reset mechanism becomes increasingly difficult as the dimensions of actuators are scaled down. Therefore, actuators have been developed in which the actuation and reset mechanism are fabricated from a single piece of material. These actuators are referred to as monolithic actuators. Monolithic actuators are fabricated from a single piece of SMA material in which local annealing is used to selectively impart the shape memory effect (SME), while the remainder of the material acts as the bias mechanism. This work proposes an extension to monolithic actuators that locally varies the material composition of the monolithic component to exhibit different mechanical properties in select regions. This eliminates the need for local annealing by introducing regions of material unaffected by the annealing process. Additionally, incorporating regions of superelastic material to act as the bias mechanism greatly increases the actuator’s range of motion. These actuators are referred to as hybrid monolithic actuators. The creation of hybrid monolithic SMA actuators requires the development of both a fabrication technique and design tool. Varying the composition locally is accomplished by utilizing powder metallurgy fabrication techniques, specifically tape casting. Tapes of different compositions are cut, stacked, and sintered resulting in a monolithic component with mechanical properties that vary spatially. Tape casting NiTi from elemental powders is studied in this work, and tape recipes and sintering profiles are developed. In order to model the SMA behaviour of complex geometries, a finite element implementation of an existing lumped-element SMA model is developed. This model is used to design and simulate a prototype hybrid monolithic actuator. The prototype is fabricated and its performance used to illustrate the advantages of hybrid design over typical monolithic actuators.

Shape memory alloys (SMA) offer several advantages over traditional electro-mechanical devices, including: smooth, silent, clean operation; linear actuation; high power/weight ratio; scalability; and reduced part counts. These unique characteristics make them an attractive option when developing actuators, particularly at the meso- and micro-scales. However, SMAs do not typically display cyclic actuation and, therefore, require some reset force or bias mechanism in order to achieve this behaviour. Additionally, the micro-assembly of SMA material with a reset mechanism becomes increasingly difficult as the dimensions of actuators are scaled down. Therefore, actuators have been developed in which the actuation and reset mechanism are fabricated from a single piece of material. These actuators are referred to as monolithic actuators. Monolithic actuators are fabricated from a single piece of SMA material in which local annealing is used to selectively impart the shape memory effect (SME), while the remainder of the material acts as the bias mechanism. This work proposes an extension to monolithic actuators that locally varies the material composition of the monolithic component to exhibit different mechanical properties in select regions. This eliminates the need for local annealing by introducing regions of material unaffected by the annealing process. Additionally, incorporating regions of superelastic material to act as the bias mechanism greatly increases the actuator’s range of motion. These actuators are referred to as hybrid monolithic actuators. The creation of hybrid monolithic SMA actuators requires the development of both a fabrication technique and design tool. Varying the composition locally is accomplished by utilizing powder metallurgy fabrication techniques, specifically tape casting. Tapes of different compositions are cut, stacked, and sintered resulting in a monolithic component with mechanical properties that vary spatially. Tape casting NiTi from elemental powders is studied in this work, and tape recipes and sintering profiles are developed. In order to model the SMA behaviour of complex geometries, a finite element implementation of an existing lumped-element SMA model is developed. This model is used to design and simulate a prototype hybrid monolithic actuator. The prototype is fabricated and its performance used to illustrate the advantages of hybrid design over typical monolithic actuators.