Al_3(Sc_(0.75)M_(0.25)(M=Ti,Y,Zr,Hf)金属间化合物有序化行为和力学性能的第一性原理计算

First-principles Calculations of Ordering Behavior and Mechanical Properties of Al_3(Sc_(0.75)M_(0.25)(M=Ti, Y, Zr and Hf) Intermetallics

采用亚晶格模型,辅助以第一性原理总能计算,研究了Ll_2型Al_3Sc基金属间化合物中元素的占位有序化行为和力学性能。结果表明:Al_3Sc合金呈现完全有序化,其中Al占据3c亚晶格位置,Sc占据1a亚晶格位置;L1_2-Al_3(Sc_(0.75)M_(0.25))金属间化合物(M=Y.Ti,Zr,Hf)也呈现完全有序化,第三组元M均只占据1a亚晶格位置,这些元素的占位行为均不受温度的影响。L12-A1_3(Sc_(0.75)M_(0.25))金属间化合物均满足力学稳定性条件。当M为Y时,L12-Al_3(Sc_(0.75)M_(0.25))金属间化合物的剪切模量、体弹模量和杨氏模量和硬度下降;当M为Ti、Zr或Hf时,随着原子半径增大,剪切模量、体弹模量、杨氏模量和硬度逐渐降低,其中Ti的加入可使L12-Al_3(Sc_(0.75)M_(0.25))金属间化合物的塑性和韧性达到最好。

The ordering behavior and the mechanical properties of the doped L12 type Al3Sc-based intermetallics were studied by sublattice model supported by first-principles calculations.The results show that the intermetallics Al3Sc is a fully ordered intermetallics,where Al atoms always occupy the 3c sublattice and Sc atoms always occupy the 1a sublattice.L12-Al3(Sc0.75M0.25)intermetallics(where M=Y,Ti,Zr and Hf)is a fully ordered intermetallics,where M always occupies the 1a sublattice.The site preference of these alloying elements is independent of the heat treatment temperature.L12-Al3(Sc0.75M0.25)intermetallics satisfy the mechanical stability conditions.The shear modulus,elastic modulus,Young’s modulus and the hardness of L12-Al3(Sc0.75Y0.25)intermetallics are smaller than those of L12-Al3Sc.While the shear modulus,elastic modulus,Young’s modulus and the hardness of L12-Al3(Sc0.75M0.25)intermetallics,where M=Ti,Zr or Hf,decrease with increasing the atomic radius.L12-Al3(Sc0.75Ti0.25)has the best plasticity and toughness compared with other L12-Al3(Sc0.75M0.25).