Atomistic deformation modes and intrinsic brittleness of Al4SiC4:A first-principles investigation
From crystallographic point of view, Al4SiC4 can be described as Al4C3-type and hexagonal SiC-lype structural units alternatively stacked along 0001 direction. However, relationship between this layered crystal structure and mechanical properties is not fully established for Al4SiC4. except for the reported bulk modulus locating between those of Al4C3 and SiC. Based on the first-principles pseudopotential total energy method, we calculated the elastic stiffness of Al4SiC4, and reported on its ideal tensile and shear stress-strain relationships considering different structural deformation modes. Elastic properties of Al4SiC4 are dominated by the Al4C3-type structural units and exhibit similar results with those of Al4C3. Furthermore, the atomistic defor mation modes of Al4SiC4 upon tensile and shear deformations are illustrated and compared with A14C3 as well. Since the tension-induced bond breaking occurs inside the constitutive Al4C3-type unit, the ternary carbide has similar ideal tensile strength with Al4C3. On the other hand, despite the softening of strong coupling between Al4C3-and SiC-type structural units is involved in shear, the shear strength for Al4SiC4 is. however, lower than the tensile strength, since p-state involved Al-C bonds respond more readily to the shear deformation than to tension. In addition, based on the comparison of strain energies at the maximum stresses, i,e,. ideal strengths, for both tension and shear, we suggest that structural failure occurs in tensile deformation firstly and. thus confirms, an intrinsic brittleness of Al4SiC4. For crystal structure arranged in alternatively stacking configuration, such as Al4SiC4, mechanical properties can be traced back to the constituent units, and are also related to the coupling strengths between each constituent unit. The results might provide a computational method to predict ductile or brittle response of a solid to applied deformations.
Ting Liao Jingyang Wang Yanchun Zhou
Shenyang National Laboratory for Materials Science, Institute of Metal Research,Chinese Academy of S Shenyang National Laboratory for Materials Science, Institute of Metal Research,Chinese Academy of S Shenyang National Laboratory for Materials Science, Institute of Metal Research,Chinese Academy of S
国际会议
杭州
英文
74-80
2007-04-01（万方平台首次上网日期，不代表论文的发表时间）