Ref.: MmeCo09-006
Apresentador: Thassia Félix de Almeida
Autores (Instituição): Almeida, T.F.(Universidade de São Paulo); Prada Ramirez, O.M.(Universidade de São Paulo); De Melo, H.G.(Universidade de São Paulo);
Resumo:
Due to their lightness and adequate mechanical properties, high mechanical strength aluminum alloys are considered a strategic class of materials for application in space, but knowledge of the damage caused by radiation to the properties of these materials still remains a major challenge. Two main aspects are desirable for the selection of new Al-based alloys as future space materials: a hardening phase capable of withstanding high doses of irradiation, but which also offers a matrix capable of resisting the development of dislocation damage. Merging the most beneficial properties of existing commercial aluminum alloys is crucial for a new aluminum alloy design strategy, creating a "crossover" between different alloy classes. For aluminum, crossover alloys can combine characteristics of heat-treatable and non-heat-treatable wrought alloys in wide compositional tolerance and with broad application ranges, establishing a universal alloy concept. Using the crossover principle, a new aluminum alloy was recently produced by metallurgically fusing two classes of aluminum alloys, the AlMg and AlZnMg alloys (AA5xxx/AA7xxx). Crossover alloys have the potential to outperform existing commercial aluminum alloys in areas where mechanical strength and corrosion are the main engineering requirements. In addition, the available research provides strong evidence of the feasibility of combining high reinforcement capacity and good formability in a single alloy system. This work studied the corrosion resistance of a new alloy formed by metallurgically fusing the beneficial properties of 5xxx series alloys (AlMg) with 7xxx series alloys (AlZn), called AA5xxx/AA7xxx-crossover. The investigation was carried out by combining characterization techniques (SEM-EDS) with electrochemical techniques (EIS and Potentiodynamic Polarization). SEM analyses showed that the surface of the AA5xxx/AA7xxx-crossover alloy is more homogeneous, with a significant reduction in intermetallic particles when compared to the 5083 and 7075 alloys. The EIS results and potentiodynamic polarization curves showed that the crossover alloy, when immersed in 0.1M NaCl, had greater corrosion resistance than the 7075 alloy. SEM analysis after the electrochemical tests showed that the crossover alloy had less corrosion product compared to the 7075 alloy. Therefore, the AA5xxx/AA7xxx-crossover alloy is very promising for the consolidation of an entirely new class of commercial aluminum alloys.