Oxidation Analysis of pure Mg processed by ECAP and cold rolling

Full text: Magnesium is one of the lightest structural metals. It has important applications in the automotive and aerospace industries, where the use of lightweight materials results in lower fuel consumption (decreasing the emission of pollutants and global warming). However, there are two major challenges to overcome: low melting point (~ 650 ° C) and high rate of corrosion and oxidation [1]. Mg alloys are also potential for hydrogen storage in solid state (metallic hydrides). The MgH₂ has the highest capacity (7.6 wt% of H) between reversible hydrides. The drawbacks are slow reaction kinetics, high operational temperatures, and poor air resistance (oxidation). The MgO layer forms a barrier which cannot be penetrated by hydrogen. Nanocomposites by mechanical alloying have been shown improved kinetics. But, severe plastic deformation (SPD) methods, such as equal channel angular pressing (ECAP) and cold rolling (CR), can be used to produce grain refinement in bulk forms. With lower surface/volume ratio and favorable textures these materials present better air resistance [2]. The aim of this work was to study the oxidation properties of cast commercial pure magnesium processed by ECAP (room temperature, 25 mm/min, 1 pass) followed by CR (20 passes). Structural characterizations were carried out by XRD and SEM, and the oxidation properties by TG/DSC (under a mixture of 80% of O₂/ 20% of N₂). XRD patterns showed that SPD methods produced different preferred orientations in Mg, along (101) plan for ECAPed and (002) for rolled. The processing routes reflected on oxidation properties, and they can produce safer and with higher ignition point samples. References [1] Y. Chunmiao, et al. J. Hazardous Mat. 260, 707–714 (2013). [2] A. M. Jorge, et al. Int. J. Hydrogen Energy 39, 3810-3821 (2014). (author)