Theoretical tensile strength of an Al grain boundary

The ab initio tensile test has been applied to an Al ∑9 grain boundary by using the ab initio pseudopotential method. The theoretical tensile strength is 9.50 GPa at the strain 21%. As compared with the theoretical tensile strength in the direction [001] or [111] of an Al single crystal, the boundary is still strong due to the interface reconstruction. The interface extends at almost the same rate with the bulk interlayer until the strain of 19% in spite of the reduced number of interfacial bonds, which indicates the special strength of the reconstructed bonds. This feature can be regarded as a typical property of Al that strong local bonds are formed for less-coordinated atoms at defects.