The production of light metal matrix composites (MMCs) using coated fiber prepregs processed by thixoforging offers several advantages over well-established technologies like squeeze casting and diffusion bonding. In order to obtain the required globular microstructure prior to thixoforging, reinforcement fibers are coated with the matrix material by twin wire arc spraying. Damage to the sensitive fibers is avoided by reducing the thermal load via optimized cooling. This study analyzes the influence of spraying parameters on the microstructure and mechanical properties of MMCs. An innovative method for automated the coating of reinforcement fibers is presented.

Thermal spraying and thixoforging technologies can be combined in a new manufacturing method for the production of light metal matrix composites. Laminated prepregs are produced by coating unidirectional fiber bundles with light metal matrix material. The prepregs are heated up and densified by thixoforging to near net-shape composites. Compared to conventional technologies for the integration of fibers in light metal matrices, like squeeze casting, hot pressing and diffusion bonding, this method offers the possibility to realize complex component geometries with short cycle times. Due to its high deposition rate and reduced thermal load on the substrate, the arc wire spraying technique is used for the coating of fiber bundles with the matrix material (AlSi6). The final fiber volume content of the MMC can be tailored by the thickness of the coating. Prior to the coating process, a continuous fiber strand is coiled on a cylindrical workpiece with adapted dimensions by using a winding unit provided with fiber guiding system. The speed and horizontal range of the fiber guide unit can be continuously varied in order to control overlapping and ensure homogeneous thickness of the fiber layer. An efficient air cooling system is installed in order to control the thermal load, which affects the formation of microcracks and influence the final residual stress distribution in the coating. An innovative method to wind and coat continuous fibers for manufacturing fiber reinforced light metal matrix composites will be presented.

For the manufacturing of metal matrix composites, a combined process of thermal spraying followed by forging in the semi-solid state can be applied. In previous work, it has been shown that thermal spraying leads to a globular microstructure that is suitable for semi-solid forming. Thereby, penetration of the spray material into the reinforcement phase leads to reduced matrix flow paths and thus reduced forming time and fiber disarrangement during the forming process. The main requirement is a low substrate and coating temperature during matrix deposition. By control of the process temperature, geometrical accuracy of the prepreg material and it’s handling between each process step can be significantly improved, leading to an economical method that is a superior alternative to the well established MMC processes like diffusion bonding or squeeze casting. Moreover, due to low process temperatures and process time during matrix application, chemical attack of carbon fiber reinforcements can be reduced. Process development for the manufacturing of continuous fiber reinforced prepregs was focused on the analysis and control of particle properties and substrate temperature. In order to improve the temperature control during arc wire spraying, numerical process analysis of the cooling system was applied. Particle in-flight analysis with the SprayWatch system was used to obtain direct spray parameters as input data for the numerical models. The simulation results were verified by experimental infrared thermography of the substrate during coating. By the use of an optimized cooling system, dense coatings without cracks were achieved with different coating thickness, thereby tailoring the fiber volume content of the final MMC component.