Increasing of the secondary silumins fracture resistance

Abstract

The purpose of the work was to analyze the influence of complex refining and modifying treatment on the microstructure, fracture resistance, physical-mechanical and service properties of secondary silumines. The material of this study were the AK9M2 and AK8M3 silumines, which were obtained from low-grade charge. It is shown that increasing of secondary materials proportion in the charge the alloy structure becomes not ordered and differentiated, with increasing of intermetallic phases number having unfavorable shapes, big sizes and irregular distribution.
The analysis of alloy fracture micromechanisms showed that in conditions of static tensile, low and high cycle fatigue the Al₅SiFe phase, which has a monoclinic lattice and large sizes, is largest contributor to the fracture processes. The tendency of the Al₅SiFe phase under static and cyclic loads to delamination and formation of microcracks in it, which pass into the metal substrate, is established.
In order to effectively improve the quality of secondary silumin and to provide the required level of mechanical, technological and operational properties, a research refining and modification complex was developed. The conducted researches showed the high efficiency of the worked out refining and modifying complex, which allowed to significantly improve the microstructure of the test alloys, to increase the level of physical and mechanical properties and the resistance to fracture. The scientific novelty is the establishment and scientific substantiation of the technological bases of formation of microstructure, physical-mechanical and service properties of secondary silumines. The practical importance of the work lies in the proposed improvement of technological processes, which due to the highly efficient refining and modifying complexes provides a significant increasing in the fracture resistance, physical, mechanical and service properties of silumines obtained from low-grade charge.