Research On Electronic Theory Of Trace Scandium And Zirconium Compound Alloying For Al-Fe Alloy

Reseaeching the enrichment phenomenon of Sc and Zr based on testing therefinement effect of trace Sc and Zr compound to Al-Fe alloy clearly in this paper. Andestablishing the atomic group model of alloy solid solution, precipitation phases and so onwith the method of empirical electron theory of solids and molecules based on the alloymicro-electron theory. Then calculating the valence electron structure ofα-Al, Al₃Sc,Al₃Zr and Al₃Fe compound phases and Al-Sc-Zr, Al-Fe-Sc-Zr cells by using BLD method.Analysising and researching the interaction of each element in Al-Fe alloy, which can helpto analysis the refinement metamorphic mechanism profoundly in the micro-electroniclevel of Sc and Zr compound to Al-Fe alloy. Especially for the metamorphic mechanism ofnucleation and growth about the primary Al₃Fe phase in Al-Fe alloy. Revealing thestrengthen mechanism of Sc and Zr compound to Al-Fe alloy in the theory to provide basictheory basis for the preparation of high strength, toughness, heat-resisitant andabrasion-resisitant Al-Fe alloy in general casting condition. Through the analysis combinedwith experiment and valence electron structure calculation, the main conclusions of thispaper:1. Adding trace Sc and Zr to Al-Fe alloy has obvious refining effect, the morphologyof the primary Al₃Fe phase turns from thick needle plate-like to small needle flake, flowerand granular shapes.The mechanical properties of alloy have been improved obviouslybecause of microstructure refinement and uniform distribution.2. The Sc-Zr key is the strongest bond in the Al-Fe-Sc-Zr cell and the Al-Sc, Al-Zrkey is the second one, which lead to the priority form Al-Sc-Zr partial poly area. It caneffectively block the combination of Fe and Al atoms, causing the compositionundercooling. The primary Al₃Fe phases turn to small needle and granular plate-likebecause it is surrounded by nucleation rich iron phase that is too late to branch. It isconsistent with the experimental phenomenon of the Sc, Zr concentration around rich iron phase.3. The Al-Fe-Sc-Zr alloy melt precipitation of many small dispersion of Al₃Sc, Al₃Zr,and Al₃(Zr_xSc_1-x)particles due to the atomic partial poly of Al-Sc-Zr.The particles canrefine Al grain and flower-like eutectic Al₃Fe phase as the heterogeneous nucleation core.For that the Al-Fe alloy has dispersion strengthening and fine-crystal strengtheningwhich can improve the mechanical properties of the alloy. It is consistent with theexperimental phenomenon of the Sc, Zr mainly exist in the Al matrix and flower-likeAl₃Fe phase.