The He doped Al Σ3 grain boundary (GB) is investigated by using a first principles method. The segregation energy and elastic coefficient of He doped Al Σ3 GB are calculated. The theoretical tensile tests on the He + Σ3 GB are implemented and the calculated stress-strain curve shows that He doping will reduce the strength of the material and induces a double stress maxima effect in the fracture process. The bondlength and charge distribution analysis indicate that the reducing strength of the He-doped GB model can be attributed to the weak interaction of the Al-He bond and the weakening of the Al-Al bond nearby the He atom.
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