Soft magnetic materials have been widely used in electric motors, routers, and detectors. Tremendous studies have been conducted to report microstructural features corresponding to magnetic performance. The laser-based powder bed fusion (L-PBF) additive manufacturing technique was implemented to bulk-scale fabricate the Finemet nanocrystalline magnetic alloy. This research study aims to reveal the capability of replacing the traditional melt spinning process with decent bulk density and magnetic properties. Nanocrystalline materials originate from optimizing amorphous metallic alloys, resulting in low coercivity and high saturation magnetization by facilitating the formation of nanocrystals. An extremely high cooling rate is the foundational factor for controlling the microstructure. Selective Laser Melting (SLM) offers a layer thickness of 20-100 µm, naturally providing a cooling rate of 105 - 107 K/s. Subsequent melting will impact the microstructure by conducting heat continuously through the melt pools. The relationship between microstructural features and crystalline phase characterization is discussed. Magnetic characterization, in terms of saturation magnetization and coercivity, with various processing parameters, is investigated. / Master of Science / Additive manufacturing of Finemet soft magnetic materials to approach expected microstructure and magnetic properties open up the path of replacing traditional manufacturing techniques. Freedom of complicated near net morphology design and inter-layer microstructural control by manipulating processing parameters offer revolutionary fabrication process comparing to traditional casting and welding. The magnetic performance of soft magnetic materials in real life applications such as electric motor is depending on multiple factors. Thus, the fascinating magnetic properties of soft magnetic materials owing strict requirement of microstructure and crystallite size. Aside from magnetic properties, as-printed bulk density fabricated by SLM would hugely impact the overall mechanical properties and porosity. Thus, processing parameters optimization through experiment and characterization would significantly benefit this study. Afterwards, comparison groups of samples with decent bulk density were taken into characterizations to reveal the crystalline phases, microstructure of metallic phases with respect to the melt pool morphology and then magnetic property of coercivity and saturation magnetization were carefully analyzed.

La thèse résulte d'une collaboration entre le laboratoire académique G2Elab et les entreprises Aperam Amilly et Aperam Imphy.Les matériaux magnétiques nanocristallins de type Finemet sont constitués d'une phase nanocristalline et d'une phase amorphe. Cette structure singulière leur confère des anisotropies magnéto-cristalline et magnéto-élastique évanescentes. On peut alors induire, par le biais de recuits adaptés, une anisotropie contrôlée conditionnant la forme du cycle d’Hystérésis et la perméabilité. D’un point de vue applicatif, il s’agit d’une aptitude capitale puisque les caractéristiques du circuit magnétique peuvent être adaptées pour répondre à des cahiers des charges spécifiques. La mise au point des protocoles de recuit mis en œuvre industriellement est cependant empirique.Le sujet de la thèse porte donc sur la mise au point d'un modèle capable de prédire l'amplitude K_u de l'anisotropie induite sur ces matériaux en fonction des paramètres du recuit sous champ (température T_re, champ appliqué H_re) et des caractéristiques structurales (fraction cristalline f_c, taille moyenne D des nanograins, composition y de la phase cristalline Fe1-ySiy). / This thesis is the result of a collaboration between Grenoble Electrical Engineering laboratory, Aperam Alloys Amilly and Aperam Alloys Imphy manufactories.The magnetic materials nanocrystalline Finemet are made of Fe-Si nanocrystallites embedded in a residual amorphous phase. This unconventional crystallographic structure features vanishing magnetocristalline and magnetoelastic anisotropies. As a result, it is possible to induce a cohenrent magnetic anisotropy in such material by suitable annealing treatments, allowing to control the shape of the hysteretic loop and permeability. In view of applications in electronic devices, this attract a great interest, the magnetic circuit characteristics being could be easily adapted by this way to satisfy the requirement of the regarded sensor or actuator.However, the optimization of annealing parameters (temperature, duration, amplitude of applied field…) to fit the desired properties is focused on time and resources consuming, which are based on empirical experience at present.As a result, the aim of this work is to build a model which will be able to predict the magnitude of induced anisotropy according to the field annealing parameters and the structural ones (crystalline fraction f_c, size of nanograins D, and composition of FeSi phase).

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В настоящей работе объектом исследования является магнитомягкий аморфный сплав системы Fe-Si-Nb-Cu-Mo-B из группы материалов Finemet. Образец выполнен в виде ленты толщиной 20…30 мкм методом быстрой закалки (спиннингованием). Для определения температурных интервалов фазовых и структурных превращений в исходно аморфном сплаве были использованы методы калориметрии, дилатометрии, терморентгеновского фазового анализа. При скоростях нагрева 0,3…0,5 o/сек установлен температурный диапазон существования данного сплава в нанокристаллическом состоянии. / The research object in that work is magnetically soft amorphous Fe-Si-Nb-Cu-Mo-B alloy. That and same alloy systems was named as Finemet material. The sample is an amorphous ribbon, which has thickness of 20…30 μm, it was producing by melt spinning method. The samples were studied using methods of calorimetry, dilatometry and non-ambient x-ray diffraction analysis. The alloy was heat treated. Data about thermal effects, changes in geometric dimensions, changes in the phase composition, and about critical points are obtained. Interval of nanocrystallic state existence for heating rate 0.3…0.5 o/sec was determined.