Авіаційно-космічна техніка та технологія (Aug 2022)
The justification of scandium selection for microalloying and modifying of high-strength aluminium alloys
Abstract
The substantiation of the scandium selection for microalloying and modifying of high-strength aluminum alloys. The research material is a high-strength aluminum alloy B96C1 of the Al-Zn-Mg-Cu system. Scandium was chosen as a microalloy and modifying element. The state diagram of Al-Sc, physical, and mechanical properties of scandium have been studied. Modes of heat treatment of B96C1 alloy with 0.3 % scandium have been developed. The structure and mechanical properties of the modified alloy were studied. The conducted complex of studies confirmed the microleveling and modifying the action of scandium in Al-melt, the technology of the introduction of scandium into melt-melt was developed, the amount of Sc was optimized. AlSc alloys have a significant effect on artificial aging. The study of the kinetics of the decomposition process showed the supersaturation of the solid solution obtained by crystallization. During the decomposition of a solid solution of scandium in aluminum, particles of the stable phase of Al3Sc are released. Based on the analysis of the Al-Sc state diagram, the homogenization temperatures of hardening and aging of the aluminum alloy B96Ts1 with optimization of the cooling rate of the workpieces were selected. In the modified blanks, grain grinding was achieved 2.5 times and the characteristics of the yield strength and yield strength of the alloy while maintaining plasticity. For aluminum alloy B96Ts1, the choice of scandium as a microalloying and modifying element is justified in terms of compliance with its physicochemical nature and properties of aluminum-based alloys. Because of hardening the alloys of the Al-Sc system, there is no decomposition of the solid solution with the release of Al3Sc intermetallic particles, which is a scientific novelty. The main effect of scandium is to increase the strength properties due to the formation of dispersed decomposition products of a solid solution of scandium in aluminum and preservation in heat-treated semi-finished products of stable structure with small subgrains. The establishment of the technology of the introduction of scan-action into the melt and temperature-time parameters of heat treatment of workpieces allowed to obtain a dispersed structure and a high set of mechanical properties of the alloy B96Ts1, which is the practical value of the work.
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