Abstract. The demand for lightweight structures in the automotive and aerospace industry increases permanently, and the importance of lightweight design principles is also increasing in other industrial branches, aiming towards improved energy efficiency and sustainability. Light metals are promising candidates to realize security relevant lightweight components because of their high specific strength; and amongst them, aluminum alloys are the most interesting materials due to their high plasticity and strain to failure, good processability, passivation in oxygen containing atmosphere, and low cost. However, for many applications, their stiffness as well as strength and fatigue behavior at elevated temperature are insufficient. Metal matrix composite (MMC) formation by integration of reinforcements in the form of continuous or discontinuous (short) fibers can yield a high increase in the alloys' specific mechanical properties at room temperature and at elevated temperature. The integration of fibers with conventional manufacturing techniques like squeeze casting, hot pressing or diffusion bonding leads to restrictions in the component's geometry. Moreover, these techniques result in elevated process costs mainly caused by long cycle times and the need of additional protective fiber coatings. In the present paper, an alternative method for the manufacturing of aluminum matrix composites is described, combining thermal spraying and semisolid forming (thixoforging) technologies for the formation of fiber prepregs and subsequent forming with simultaneous densification. Therefore, prepregs with the matrix alloy as a thick surface coating on the reinforcement fibers are manufactured in a fast, automated coating process, while reheating, densification and shaping are performed in a separate process, allowing an optimization of both processes towards cycle times and resulting material properties.Continuous fiber and short fiber reinforced aluminum matrix composites are manufactured using woven or parallel arranged continuous fibers, or short fibers as a fleece or fiber paper material. For the coating process, twin-wire electric arc spraying is applied as a well established, cost efficient thermal spray technology. The coating process is optimized towards microstructure of the matrix alloy prior to semisolid forming, which requires a globular alloy microstructure, and reduced fiber damage during the high-temperature liquid melt deposition. The thermally sprayed fine-grained matrix material enables semisolid forming at liquid contents of 40-60 vol% of the alloy, with short flow paths, reduced mechanical loads and short cycle times. Thus, limited fiber damage and residual stresses will occur, leading to good mechanical material properties. A production line for industrial-scale coating of fiber fabric coils in a continuous process is introduced in order to provide prepregs of various fiber-reinforcement materials and fiber architectures; moreover, a winding equipment for simultaneous fiber winding and coating is presented ...

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Thermal spraying and thixoforging technologies can be combined in a new manufacturing method for the production of light metal matrix composites. This paper describes the production of unidirectional (UD) and tailored local fiber reinforced MMC based on this new method. For manufacturing of UD fiber reinforced metals, fiber prepregs are produced by coating of fiber bundles with light metal matrix material. For further processing to the final MMC, these prepregs are laminated, heated up and densified by thixoforging to near net-shape components. 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. However, the focus of this paper lies on the flexible processing of fiber prepregs with local, already near net-shape fiber reinforcement by continuous fiber deposition and simultaneous coating with the matrix alloy by thermal spraying. As a case study, the manufacturing of a wheel rim with local reinforcement in the central area will be discussed.

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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.