Microstructural and mechanical characterization of a Mg-1wt%Mn1t%Nd alloy processed by high-pressur torsion

• Autor(a) principal: Paula Campos de Oliveira
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/42080
• topic: Magnesium alloy; Severe plastic deformation; High-pressure torsion; Segregation; Engenharia metalúrgica; Metalurgia física; Deformações e tensões; Magnésio

Magnesium is the lightest structural metal with a high strength-to-mass ratio, offering considerable potential for automotive and aerospace applications. However, its use remains restricted due to its poor formability at room temperature and low strength. To improve the properties of Mg, some of the viable alternatives are alloying with rare-earth elements and subjecting the material to severe plastic deformation. The present work investigated the microstructural and mechanical evolution of a Mg-1wt% Mn-1wt%Nd processed by high-pressure torsion, and its microstructure was characterized by X-ray diffraction, scanning, and transmission electron microscopy. The segregation of alloying elements was observed with high-angular annular dark-field images, and it is typically related to higher hardness and thermal stability, enhancing the interest in understanding their formation. The results show that Nd readily segregates to grain boundaries in early stages of deformation, while Mn, which was dispersed as small particles in the starting material, undergoes slow fragmentation forming nanoparticles distributed throughout the microstructure, and segregates to boundaries in a distinctly more sluggish manner than Nd atoms. The evolution of microhardness shows a rapid increase in strength at low imposed strains until reaching saturation. It is suggested that Mn plays only a minor role in the contribution to the strength of this alloy because the slow development of nanoclusters and segregations of this element does not relevantly affect the hardness.