Thixoforged Al-Si Metal Matrix Composites Made from Thermally Sprayed Ceramic Fiber Laminates

Advanced continuous fiber reinforced light metal matrix composites (MMC) are manufactured using thermally sprayed prepregs and subsequent semi-solid forming. The prepregs consist of fiber woven fabrics, which will serve as reinforcement, and a thick metal alloy coating on top of the fabrics as the final matrix material. The coated fabrics are trimmed to the shape of the component and laminated in packages of 40 to 80 prepregs to form a component. The prepregs are reheated into the semi-solid state of the alloy and solidified to a dense, complex shaped MMC with no residual porosity by semi-solid forging (thixoforging). The deposited alloy infiltrates the fabrics with 40 % vol. to 60 % vol. liquid fraction. The fine-grained structure of the thermally sprayed metal coatings allows the required formation of globular grains during remelting and improves the impregnation behavior. The semi-solid forming and simultaneous infiltration in short cycle times offer the possibility to realize complex near net-shape geometries and make additional fiber coating not obligatory. A pilot plant was developed to provide the MMC production with prepregs consisting of various reinforcement fiber materials and a wide range of metal matrix alloys capable for thixoforging densification.