Bi,Sb及稀土元素对AZ91镁合金高温性能影响机理研究

The mechanism of the influence of Bi(or Sb) and rare earth on high temperature performance of AZ91 magnesium alloy

利用大角重位点阵概念建立了AZ91镁合金基体(α相)和镁[0001]对称倾斜晶界原子结构模型,应用实空间的连分数方法计算了体系的结构能,环境敏感镶嵌能以及相互作用能.结果发现,在镁合金基体中,Al和稀土形成团簇时比较稳定,Al,Bi或Sb与稀土形成团簇时不稳定.Bi或Sb和稀土元素同时存在于AZ91镁合金中时,一方面Bi或Sb将可与RE结合形成RE2Bi(RE2Sb)或RE-Bi(RE-Sb)化合物弥散分布于晶界,另一方面镁合金基体中会形成Al11RE3化合物,消耗了镁合金中的Al,抑制粗大非连续析出相Mg17Al12的形成;稀土与Al,Bi或Sb形成的化合物熔点较高,且晶界区RE2Bi(RE2Sb)或RE-Bi(RE-Sb)化合物的析出细化AZ91合金基体中Al11RE3相,显著提高了合金的高温性能.

The atomic structure models of α matrix and the symmetric [0001] tilt boundary in AZ91 magnesium alloy were set up by using the concept of coincidence-site lattice（CSL）.The total structure energy of α matrix and the grain boundary（GB）,the environment sensitive embedding energies（E_ ESE） of alloy elements and the interaction energies between the atom clusters were calculated by using recursion method.Calculation results show that the cluster formed by Al and RE in bulk AZ1 Magnesium alloy is rather stable,but the cluster of Al,Bi（or Sb） and RE atom is unstable.When Bi（or Sb） and RE atoms coexist in AZ91 magnesium alloy,Bi or Sb will combine with RE to form dispersed particles which are mainly RE_2Bi（or RE_2Sb） and RE-Sb（or RE-Bi） distributed at the grain boundary,and Al_ 11 RE_3 will form in the bulk in AZ91 magnesium alloy.The consumption of Al in magnesium alloy inhibits the formation of the discontinuous precipitate phase Mg_ 17 Al_ 12.The melting points of compounds formed by RE and Al（or Bi,Sb） are high,thus the high temperature performance of AZ91 magnesium alloy would be obviously improved.