Development of magnesium-based hybrids through high-pressure torsion

• Autor(a) principal: Moara Marques de Castro
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/36681; https://orcid.org/0000-0002-1663-2833
• topic: Nanostructured composites; Magnesium; High-pressure torsion; Hybrids; Particles consolidation; Engenharia metalúrgica; Metalurgia física; Deformações e tensões; Magnésio

High-pressure torsion (HPT) is a well-established severe plastic deformation technique for achieving substantial grain refinement and improving mechanical resistance in metallic materials. Besides, HPT can also consolidate metallic particles into a bulk solid disc and incorporate other materials (as hard materials, bioactive materials or other metallic materials) to tailor a variety of hybrids. The present work explores the fabrication of different magnesium matrix hybrids, developed by blending Mg particles with varying kinds of reinforcement, using HPT processing for consolidation. It is shown that hybrids with mechanical integrity can be fabricated by this method. Different characterization techniques, including optical and electron microscopy, are used to analyse the microstructural evolution of the produced hybrids. Well-dispersed second phase particles within continuous and refined magnesium matrix are obtained. The distribution of phases may be controlled by the amount of rotation imposed during processing. The mechanical properties are evaluated by hardness tests and miniature-tensile tests, showing that the composites might display improved strength and tensile resistance, indicating a good bonding of particles. Evidence of a Hall-Petch break-down was identified in a Mg alloy-alumina hybrid, and higher hardness was achieved in Mg-Zn hybrids due to grain refinement, fragmentation of phases, segregation of alloying elements along grain boundaries and precipitation of intermetallics. The hybrids produced using high-pressure torsion have different potential applications, including the development of bioactive and biodegradable implants.