Effect of pressing pressure on microstructure and selected strength properties of AlSi CF composite castings
Andrzej Zyska
Quarterly No. 4, 2023 pages 197-201
DOI: https://doi.org/10.62753/ctp.2023.03.4.4
keywords: chopped carbon fibers, AlSi matrix, squeeze casting, strength properties
abstract The results of the study of the microstructure and selected strength properties (Rm, E) of an aluminum composite reinforced with chopped carbon fibers are presented. Composite castings were produced by the combined method of mechanical mixing and direct squeeze casting. Silumin EN 44300 and carbon fibers with a diameter of 6-7 μm and a length of 5-6 mm with a metallic coating - Ni (Tenax) and without a coating (Fortafil) were selected for the investigations. Experiments were carried out for 4 pressure values in the range of 20-80 MPa and their impact on the structural homogeneity of the composites as well as the strength and elasticity of the castings was assessed. The beneficial effect of the metallic coating manifests itself directly in the properties of the composites. The tensile strength of the composites reinforced with Tenax fibers is approx. 250 MPa and is 10% higher than the Rm of the reference alloy of the matrix. This level of strength is achieved by applying a pressing pressure of 60 MPa. The lack of a cohesive connection of the fibers with the matrix and a significant number of internal defects in the structure of the composite reinforced with Fortafil fiber cause a reduction in its strength both in relation to the composite with Tenax fibers and the reference alloy. As part of the strength tests, it was shown that chopped carbon fibers cause a significant increase in the elastic properties (E) of composites with an AlSi matrix, while the effect of the preparation of the surface of the reinforcing phase as well as the pressing pressure on this property are insignificant.