| In this thesis, over one hundred samples had been melted in the furnace and screen calssification. Finally, the compositions of Al-Re-B alloys were optimized. Compared with the national standards, the alloys' general properties excelled greatly.Joined with the theoretically thermodynamic calculation, the effect mechanisms of rare-earth(RE) element and boron element which were added into aluminum were analyzed in the thesis. And the resistivity measurement of aluminum conductor, microstructure observation through the optical microscope and SEM, and phase composition analysis through the EDS were adopted in the experiments. Therefore, the mechanisms that RE and boron elements interacts with impurity elements in the aluminum were further perfected. The disputes on the mechanisms that RE and boron elements could be used to improve the conductivity of the aluminum conductors could be minished by the present works. On the basis of these, the effects of RE and boron elements on the conductivity of aluminum conductors were studied from three aspects as followed:1. The effects of boron element on the electric conductivity of aluminum conductors were studied. By analysis through the SEM & EDS and joined with the thermodynamic calculation, phase compositions and distribution in aluminum were studied and analyzed after boron element was added into aluminum. The results of research showed that boron element would react with impurity elements such as titanium(Ti) , vanadium(V) , chromium(Cr) and manganese(Mn), et al., and that complicated borides were formed, so the negative effects of the impurity elements on the conductivity of aluminum conductor could be decreased through the reaction processes. Moreover, a calculation formula for the best addition quality of boron element was educed, and the best addition quality of boron element calculated by the formula was very agreement with the experimental results. Boron element also refined the crystal gains effectively.2. The effects of RE on the electric conductivity of aluminum conductors were studied. By analysis through the SEM & EDS and joined with the thermodynamic calculation, phase compositions and distribution in aluminum were studied and analyzed after RE element was added into aluminum. The results of research showed that RE element could react with impurity elements such as iron(Fe) and silicon (Si), and the complicated RE compounds wereformed. So it could decrease the negative effects of the impurity elements Fe and Si on the conductivity of aluminum conductors. Moreover, a calculation formula for the best addition quality of RE element was educed, and the best addition quality of RE element calculated by the formula was very agreement with the experimental results. The effects of mixed RE elements differed largely from that of single RE element because of its complex compositions, a calculation formula for the best addition quality of mixed RE elements wasn't obtained, but, according to the experimental results it could be affirmed that the effects of refinement crystal gains for mixed RE elements were stronger than those of single RE element.3. The mixed effects of boron and RE elements treatment on the electric conductivity of aluminum were studied. By analysis through the SEM & EDS and combined with the thermodynamic calculation, phase compositions and distribution in aluminum were studied and analyzed after boron and RE elements were added into aluminum together. The results of research showed that the compositions were much more complex after boron and RE elements were added into aluminum. Besides the compounds of boron and RE elements, the complicated compounds of boron and RE elements reacted with the elements of Fe and Si and with Ti, V-. Fe> Cr > Zr, et al. were found. The compounds of other impurity elements also were found. At the same time, the phenomena of crystal gains refined were observed.Finally, through summing up the experimental results, it could be concluded that the essence of "boron element treatment" and "RE element treatment" was that decreased the negative effects of corresponding impurity elements on the conductivity of aluminum for boron and RE elements respectively, and the complicated RE compounds and borides were formed. The effects of impurity elements extraction were realized. At the same time, the crystal gains were refined. While holding the better electric property of aluminum conductors, the mechanical properties of aluminum conductors were enhanced. Then, the general properties of aluminum were improved to some extent Finally, a new process of mixed treatment of boron and RE elements added into aluminum conductors was brought forward in order lo farther enhance and improve the general properties of aluminum.,... |
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