| In the field of condensed matter physics and materials science, it is of great importance to investigate the microstructures, properties and solidification regularities of liquid metals. In the last few decades, the theories of rapid solidification of binary alloys, such as dendrite growth and eutectic growth have been set up. Great progress has also been made on the study of monetectic and peritectic alloys. But most of the engineering alloys are ternary or multicomponent alloys. The theories of ternary alloys have not been set up. So it is of great importance to investigate the solidification regularities of ternary or multicomponent alloys.At present, ternary quasiperitectic transformation has happened in a lot of ternary alloy systems, such as Al-Fe-Si, Al-Cu-Mg, Fe-C-Cr, Fe-Mo-Si, Pb-Bi-Sn, Cu-Ni-Sn and so on. Ternary quasiperitectic transformation involves the process in which one liquid and one solid interact with each other to produce two other solid phases, i. e. L+α→β+γ. It looks like peritectic transformation from the view of reactants, butlooks like eutectic transition from the view of products. Ternary quasiperitectic alloy systems involve very complicated phase transition and solidification process. Hence, a solidification theory on ternary quasiperitectic alloys has not been established up to now. The study of the solidification process, microstructure evolution and phase constitution of quasiperitectic alloys will provide a research foundation for developing rapid solidification theories of ternary alloys.After the quasiperitectic transformation, ternary eutectic transformation happens and the finally structure is composed with quasiperitectic structure and ternary eutectic structure. In order to investigate the microstructure of quasiperitectic, firstly, this thesis investigates the microstructure evolution and solidification process of liquid metals of ternary eutectic alloys and to improve on an algorithm for calculating the solidification paths of ternary eutectic alloys coupled with Thermo-Calc based on the microsegregation model proposed by our research group. After that, this thesis investigates the microstructure evolution and solidification process of liquid metals of ternary quasiperitectic alloys and to improve on an algorithm for calculating the solidification paths of ternary quasiperitectic alloys coupled with Thermo-Calc. The main works include:The experimental facilities of this thesis are designed, which include quenching graphite crucibles, clamp apparatus of crucibles, casting mould, thermo-couple and so on. The phase composition, microstructure evolution and solidification process of ternary eutectic Al-Cu-Mg alloys are investigated with quenching experiment and the solidification paths of Al-Cu-Mg ternary eutectic alloys are investigated. The solidification paths of Al-4.37%Cu-27.02%Mg and Al-10.68%Cu-25.00%Mg are simulated basied on the above arithmetic.After the analysis of Al-Cu-Mg ternary eutectic alloys, the phase composition, microstructure evolution and solidification process of Al-Cu-Mg ternary quasiperitectic alloys are investigated. The solidification paths and possible quasiperitectic solidification elements of Al-Cu-Mg ternary eutectic alloys are elicited. The solidification paths of Al-Cu-Mg ternary quasiperitectic alloys Al-14.15%Cu-18.40%Mg are simulated basied on the arithmetic in this thesis. |
