Additive manufacturing and processing by forming of Al-Ti metallic composites
Final Report Abstract
Cold spraying has great potential for additive manufacturing, especially of oxidation-sensitive metals, because the material is not melted and significantly higher deposition rates can be achieved than with conventional additive manufacturing processes such as selective laser melting or direct metal deposition. Titanium is regarded as a high-performance engineering material due to its unique combination of properties, including good corrosion resistance, biocompatibility and high strength at comparatively low density. However, due to its high price, it appears reasonable for many applications to use material compounds in which titanium is only used on the surface of the workpiece, while less expensive materials such as aluminum are used for the remaining volume. In the present project, cold sprayed pure titanium coatings were deposited on Al substrates and then formed to defined 3-dimensional final contours by die forging and rotary swaging. The following conclusions can be drawn from the investigations: 1. Because of their low ductility, dense, state-of-the-art, cold sprayed Ti coatings are not suited for low-temperature forming processes. 2. Cold sprayed Ti coatings with medium porosity (around 7 %) exhibit an improved forming behavior after a pre-compression step. 3. Al/Ti interlayers lead to a gradation of the deformation properties between Al and Ti, which improves the formability of Al/Ti compounds significantly and enables the manufacturing of complex die-forged geometries. 4. Crack-free Al + Al/Ti + Ti compounds can be produced by combining cold spraying and rotary swaging. 5. Rotary swaging increases both the coating tensile strength and the ductility of cold sprayed Al/Ti compounds. 6. By using the method of iterative flow curve modeling, the die forging process of cold sprayed Al/Ti compounds can be modeled in detail. In general, it can be stated that forming processes in which the cold spray coating is predominantly subjected to compressive load (as in rotary swaging), are significantly less critical with regard to crack formation. Enhancing cohesion by compressing the coating material, closing existing pores and therefore bringing non-bonded particles into intimate contact appears to be a crucial precondition for a successful forming result. This is particularly important for forming processes in which the component to be formed or areas thereof are subjected to tensile stresses. A pre-compression step proved to be a suitable strategy for ensuring the necessary cohesion in the coating for the subsequent die forging process.
Publications
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Numerical and Experimental Modeling of an Inline Forming Process for the Mechanical Property Optimization of Cold Gas Sprayed Material Composites. Lecture Notes in Production Engineering, 366-374. Springer International Publishing.
Colditz, P.; Härtel, S. & Drehmann, R.
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Forming behaviour of Al/Ti material compounds produced by cold gas spraying. 6th International Thermal Spraying and Hardfacing Conference ITSHC 2022, Wrocław, Polen
R. Drehmann, P. Colditz, M. Graf, B. Awiszus & T. Lampke
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Forming behaviour of additively manufactured Al/Ti material compounds produced by cold spraying. International Thermal Spray Conference 2023, Québec, Kanada. (Konferenzvortrag)
R. Drehmann, P. Colditz, M. Graf, A. List, F. Gärtner, B. Awiszus & T. Lampke
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Forming behaviour of additively manufactured Al/Ti material compounds produced by cold spraying. ITSC Proceedings 2023, Québec, (2023)
R. Drehmann, M. Graf, T. Lampke, P. Colditz, B. Awiszus, A. List & F. Gärtner
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Forming Behavior of Additively Manufactured Al/Ti Material Compounds Produced by Cold Spraying. Journal of Thermal Spray Technology, 33(2-3), 676-687.
Drehmann, Rico; Colditz, Pascal; Graf, Marcel; List, Alexander; Gärtner, Frank; Awiszus, Birgit & Lampke, Thomas
