B和Y对含Mn的Al-7Si-1Fe合金电导率的协同影响机制

Synergistic Effects of B and Y Elements on Electrical Conductivity of Al-7Si-1Fe Alloy Containing Mn

Mn是商用铝合金中最为常见的合金化元素之一,但其会显著降低铝合金的导电性能。通过添加B和Y对含Mn的Al-7Si-1Fe合金进行变质处理,揭示其对合金电导率的影响规律和内在机理。结果表明,B和Y能有效提高合金的电导率,其中,Y可将粗大的板条状共晶Si转变为细小的珊瑚状,同时细化合金中的长针状富Fe相,并促进固溶的Si以Al_(2)Si_(2)Y形式析出;而B则通过硼化处理,将固溶在Al中的Mn吸附在AlB_(2)上,并形成相应的硼化物析出。当B和Y复合变质时,AlB_(2)吸附Mn和Y并形成Al_(10)Mn_(2)Y吸附层,同时富余的Y对共晶Si和富Fe相进行细化,进一步提升含Mn的Al-7Si-1Fe合金的导电性能。但随着熔体静置保温时间的延长,Al_(10)Mn_(2)Y吸附层的厚度增大,Y含量的减少导致其对共晶Si的变质效果被削弱,使合金导电性能发生显著下降。

Mn is one of the most common alloying elements in commercial Al alloys,which,however,can significantly reduce the electrical conductivity of Al alloys.The Al-7 Si-1 Fe alloy containing Mn was modified by B and Y elements to reveal the influences on its electrical conductivity as well as the modification mechanism.The results indicate that B and Y elements can effectively improve the electrical conductivity of the alloys,where the coarse slate-like eutectic silicon is transformed into the fine coral-like under the condition of Y.Meanwhile,the long needle-like Fe-rich phase in the alloy is refined and the solution Si is precipitated in the form of Al_(2)Si_(2)Y.Element B can promote Mn adsorption onto AlB_(2)to form borides.Under the compound modification of B and Y,Mn and Y elements are adsorbed by AlB_(2)to generate Al_(10)Mn_(2)Y adsorption layer.Moreover,surplus Y element can refine the eutectic silicon and iron-rich phases,further enhancing the electrical conductivity of the Mn-containing Al-7 Si-1 Fe alloys.With the melt holding time prolonging,the thickness of the Al_(10)Mn_(2)Y adsorption layer is increased.Modification effect on eutectic Si is weakened due to the Y content reduction in the melt,leading to the significant decrease of conductivity consequently.