Toughness is another characteristic of the materials that can be analyzed through a stress/strain diagram. Toughness is the ability of a material to absorb mechanical energy before the fracture and can be defined as the area under the stress/strain curves. According to the results, the toughness of the powder-free and micro-alumina samples are 76 % and 36 % higher than the base metal. On the other hand, the toughness of the nano-alumina sample has decreased by 4.5 % compared to the base metal. The reduction of the latter case is because this case has become relatively more brittle than the base metal despite an increase in strength.