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The effects of micro-Ru alloying addition on NiAl alloys were investigated by optical microscopy, SEM, X-ray diffraction and powder X-ray diffraction. The mechanical properties were characterised by Vickers microhardness measurement and compression tests at room temperature and various elevated temperatures. Micro-Ru alloying addition does not modify the crystal structure of NiAl alloys. However, local electronic structure may be modified owing to the specific site occupancy preference of Ru, smaller size difference between Ru and Al and different electronic nature of Ru and Ni. This is partially verified by the decrease of the long range order degree accurately measured via powder X-ray diffraction. As a result, a maximum softening effect occurs at 0.5 at.-% Ru addition indicated by Vickers microhardness measurement and compression testing results.