The effect of modification with nanocompositions on the structure and properties of foundry silumins

Abstract


 Abstract. Problem. The difficulty of solving the problem lies not only in the improved quality of casting alloys, but also in the development of recommendations for achieving stability of the chemical composition, refining the structure, and increasing the mechanical and technological properties of castings. Goal. The goal of the work is to achieve a stable dispersed structure and increase the complex of mechanical properties of foundry silumins. Methodology. Based on the Al – Si influence diagram, the choice of cast aluminum alloys for modification with nanocompositions is substantiated. The technology of modification with nanodisperse compositions consisted in introducing powders of the complex nanomodifier Mg2Si+SiС into the aluminum melt. A mixture of Mg2Si+SiC nanopowders with a particle size of 50...100 nm, obtained by plasma chemical synthesis, was mixed for several hours in a special attritor with successive pressing of modifier tablets on an automatic press. Results. The technological process of modifying aluminum melts with a complex modifier was developed, the temperature and time parameters of the process were determined. Brinell hardness was measured on samples of AL4 and AL4C alloys, 25x25 mm in size. As a result of the obtained data, it is observed that in the modified samples of the AL4 alloy, the hardness increased by 6.9%, and in the AL4C samples – by 4.8%. The obtained hardness measurement data are consistent with the results of testing the strength properties of alloys before and after modification. Originality. In the modified alloys, a higher fluidity than in the initial state and a homogeneous dispersed microstructure were obtained. Practical value. In the modified alloys, an increase in strength properties was achieved: σv by 9 - 10%; σ0.2 by 11-12%, while maintaining the level of plasticity. The impact strength of modified alloys is significantly increased by 20-30%. As a result of the conducted studies of the structure and properties of cast alloys AL4 and AL4C, the effect of modification with nanodisperse compositions was confirmed.