Effects Of Boron And Erbium On Microstructure And Thermal Conductivity Of Al-Mg-Si Alloy

This study has investigated the Al-Mg-Si alloy used as heat conduction. By testing thermal diffusivity, density, specific heat and calculating thermal conductivity, the influence rules of improving the thermal conductivity with adding B and Er are analyzed. The influence mechanisms of the B, Er and impurity elements in Al-Mg-Si alloy are explored by means of OM, SEM, EDS, XRD. Analyzing the effects on the microstructure, thermal conductivity and tensile properties of Al-Mg-Si alloy with interaction of the B and Er were investigated by using the method of orthogonal analysis. The main results are listed as follows:With increasing B content, refining effects of Al-Mg-Si alloy are greatly improved.When the B content reached to 0.2% the refining effects are best. The refining effects are not change obviously when the B content is over 0.2%. The thermal conductivity is improing with increasing B content at room temperature. When the B content reached to 0.2% the thermal conductivity is 239.1W/(m·k),Which is the best.whereas the thermal conductivity decreased when the B content is over 0.2%.The dendrite spacing is decreased obviously in grains when the Er content is less than 0.25%, but the grain size is not changed obviously. When the Er content increased to 0.35%, the dendritic structure is disappeared and the grain size decreased obviously. The refining effect had little change when the Er content increased continuously. The thermal conductivity is improing with increasing Er content at room temperature. When the content reached to 0.25% the thermal conductivity is 223.0W/(m-k), Which is the best.whereas the thermal conductivity decreased when the content is over 0.2%.The combined addition of B and Er could lead to the result that the structures of alloy become coarser, but does not contribute additive effects to thermal conductivity. By the means of range analysis, influence on thermal conductivity of B is the highest, followed by the soaking time after the addition of B, and finally was Er.The precipitate of boride such as TiB2, V2B3, Cr2B can be formed when B combined with Ti, V, Cr in Al-Mg-Si alloy which can eliminate the influence of impurity elements on thermal conductivity. The content of Fe, Si in solid solution of matrix is decreased when B combined with Fe, Si in Al-Mg-Si alloy, which thus lead to that separate addition of B and Er can improving the thermal conductivity of alloy. The ErB2, ErB12 firstly forms in alloy by the compound addition of B and Er.Hindering B and impurity elements form boride and hindering Fe combined with Si to make compounds.This cannot effectively eliminate the influence of impurity elements on heat conductivity, which is unfavourable improving the thermal...