The Effect Of Excess Mg, Si On The Properties Of6101Conducting Wire And Exploring The Mechanism

In this thesis,6101conducting wire were investigated by specific experiment operations and first principle method, for exploring the effect of excess Mg, Si on the conductivity and mechanical properties of6101conducting wire and the mechanism.In this work, keeping all of alloys contain0.95wt.%Mg2Si in theory. Then, making the alloys transform from excess of Mg to excess of Si by adding Si or Mg element, while the Mg/Si changing with a certain order. The alloys before and after heat treatment were investigatedby the ways of conductivity measurement, tensile test, XRD, and microstructure analysis. The results showed that, to the alloys without heat treatment, it has negative correlation between conductivity and content of the excess elements.But strengthis not positively related to excess elements. The alloys with excess Mg, after aging, one side, Mg would still exist in matrix and cause lattice distortion. On the other hand, the solubility of precipitates would be significantly reduced and easily turn to coarse phase causing by excess Mg. The changes in this two aspects restrict the improve of conductivity and mechanical properties; To the alloys with excess Si, after aging, the excess Si separate from the matrix, which decreases the degree of lattice distortion and promote the precipitation of β".In addition, excess Si reduces the bad effect of Fe by forming AlSiFe ternary phase. So excess Si does good for improving alloy’s conductivity and mechanical properties.On the other hand, the results of first principle revealed the physical properties of β",β’, β. Although in the aspect of thermodynamics stability, β",β’ belong tometastable phase, both of the three meet the conditions of Born criterion, indictated that they have good a structural stability. The precipitation of β",β’,β increase the alloys’ strength for they have larger shear modulus than matrix. Inspecific experiment, β" was found to be the most important precipitated phase, the first principle calculation explanations this phenomenon from the viewpoint of quantum mechanics. Theelasticity modulus and shear modulus of β’, β are 57.93GPa,44.21GPa and97.01GPa,105.28GPa, which biger than β" and α-A1matrix’s26GPa,28.71GPa and76GPa,54.38GPa. So dislocations pass though β’,β just by the Orowan mechanism, in contrast, dislocations cross β" mainly by Cutting mechanism. At the same time, in there are more free electrons near the Fermi level in the energy band structures of β". So it’s more easy to occurrence of conductive than β’,β.Taken all of the factors into consideration,it’s give a reasonable explanation of why β" makes the greatest contribution to improve the conductive and mechanical properties of6101conducting wires.