Resumen de Influence of al and zn alloying additions on the deformation mechanisms of mg alloys
Magnesium alloys, as one of the lightest structural materials, continue to receive significant attention for weight-saving applications, particularly in the automotive, electronics, and aerospace industries. However, the widespread industrial application of these materials remains limited due to their low strength and to their intrinsic poor room temperature ductility, which restricts applications in damage-tolerant structural components. The low ductility and forming ability of magnesium are due to its hexagonal close-packed (hcp) crystal structure with limited number of available deformation modes, which induces plastic anisotropy and intrinsic brittleness. At room temperature Mg alloys deform mostly by basal slip and tension twinning, while the activity of non-basal slip systems is generally limited. Several strategies have been put forward to improve the formability and the fracture toughness of Mg alloys, with different degrees of success. It is known that solid solution alloying leads to enhanced Mg ductility and formability at relatively low concentrations. Al and Zn are the two most common solutes and are significantly more cost effective than rare earth elements. However, the intrinsic mechanisms by which the addition of solutes leads to a ductility improvement are still controversial. In turn, precipitation strengthening has not been as successful in Mg alloys as in Al alloys, and the mechanisms of interaction between dislocations and twin boundaries and precipitates are still not well understood. This PhD thesis constitutes an attempt to better understand the relationship between the microstructure, the active deformation mechanisms, and the mechanical properties in polycrystalline binary solid solution magnesium alloys with Zn and Al additions, both at room and high temperature, and in an aged ternary Mg-Mn-Nd alloy with Zn additions containing ultrafine precipitates.
