It is known that aluminum alloys can be classified as alloys for the production of castings and wrought alloys (rolling, extrusions, forgings and others). Wrought aluminum alloys are subdivided into heat-treatable alloys, those that respond to heat treatment to increase their mechanical strength and non heat-treatable alloys, whose mechanical properties can only be improved by cold working. The use of aluminum alloys has a great advantage due to the strength / weight ratio of Al, it has been used in industrial applications to different solutions, such as in the construction of automobiles, aerial and space vehicles, packaging and in overhead transmission lines. This paper aims to analyze the effect of heat treatment on the microhardness, ultimate tensile strength and in the elongation of the Al-0,18%Zr; Al-0.18%Zr-2.0%Mg and Al-0.18%Zr-6.0%Mg alloys compared to results obtained without heat treatment. The alloys were melted in a muffle furnace and cast in a water-cooled Cu mold. Samples were cutt and machined to a diameter of 9.5 mm, subsequently being heat treated at 400°C for 16h. The For mechanical characterization, Vickers microhardness test and tensile test were performed The ultimate tensile strength and the elongation of the alloys before and after heat treatment were evaluated. The results showed that increasing Mg contents caused grain refinement, gains in microhardness values, ultimate tensile strength and losses in elongation. However, after the heat treatment, the elongation of Al-0,18%Zr-6,0%Mg alloy presented significant value, that can be explained by the phenomenon of superplasticity.