Production of three-dimensional single-crystal with directional solidification

Single-crystal materials exhibit superior mechanical, thermal, and electrical properties compared to their polycrystalline counterparts, thus rendering them crucial for aerospace and electronics industries. The aim of this project was to demonstrate the feasibility of obtaining three-dimensional single-crystal materials from polycrystalline counterparts through controlled Bridgman-type directional solidification experiments. Parameters such as temperature gradient and growth velocity were controlled, and grain selectors with different geometrical parameters were used during solidification experiments. The successful production of single-crystal material from a polycrystalline 1050 aluminum alloy was confirmed through grain structure analysis of the solidified samples, affirming the project's objectives.

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Understanding the solidification dynamics of 1050 aluminum alloys manufactured by the twin-roll continuous casting technique and determining the suitable composition for casting efficiency

Aluminum alloys are widely used in many industries, from packaging to aviation, due to their superior properties, and the use of aluminum continues to increase rapidly all over the world. Aluminum materials are produced using many different methods such as casting, forging, extrusion and rolling. The twin-roll continuous casting method, which combines casting and rolling, is widely used in the production of sheet products. Despite its widespread use, cooling rates and solidification dynamics are not well understood. In this project, Bridgman-type directional solidification experiments were carried out at different velocities and the cooling rates and solidification dynamics obtained by the twin-roll continuous casting technique were determined. The microstructural components obtained in the laboratory environment were quantitatively matched with the ones formed in different regions along the thickness of the strips obtained on an industrial scale. At the same time, the optimum alloy composition with minimum latent heat and narrow solidification range was determined in order to increase production efficiency.

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Dynamics of three-phased eutectic growth of isotropic systems

The study of growth dynamics includes examination of periodic steady-state microstructures in 2D, quasi-2D, and 3D specimens in model alloys such as In-Bi-Sn system. Limits of morphological stability, material constants such as diffusion, Jackson and Hunt constants are also within the interest of this group. Determination of a stability map of microstructures as functions of the characteristic eutectic spacing, crystal growth velocity, specimen thickness, and alloy composition is the ultimate goal which will enable us to predict and hence to control the microstructural features. This will create new solidification paths for novel structures and hence lead to remarkable physical properties of materials.

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Effects of anisotropy on ternary eutectic systems

The contact surfaces of crystals generally exhibit a certain degree of anisotropy. In other words, the interphase surface energy is a function of the crystallographic orientation of the phases. This implies that the eutectic-solidification dynamics should depend on the orientation of the eutectic phases with respect to each other and to the temperature gradient. Indeed, many alloys exhibit orientation relationships, such as Kurdjumov-Sachs relation, corresponding to low-energy interphase boundaries at fixed crystal orientations. The competition between isotropic and anisotropic grain dynamics is conjectured to be a key factor for the formation of solidification textures in epitaxial systems. Hence, the aim of this project is to investigate the effects of anisotropy in In-Bi-Sn and Al-Cu-Ag ternary eutectic systems using 2D and 3D specimens and various solidification techniques.

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Growth of faceted/nonfaceted eutectic structures

There exist many remaining questions regarding faceted/nonfaceted eutectic alloys although they have been extensively used in the industry. The goal of this project is to investigate and characterize various microstructures obtained in Cu-B and AMPD-SCN systems employing different compositions and growth conditions. Crystallographic orientation of the boron phases is also examined to understand the relation between the microstructure and the crystallographic orientation. After establishing the stability map and the physical properties of the system, new application areas are expected to be generated for boron products.