Consolidation of Magnesium and Magnesium Alloy Machine Chips Using High-Pressure Torsion

Castro, Mirian Cabral Moreira de; Carvalho, Amanda P.; Pereira, Pedro Henrique R.; Neta, Augusta Cerceau Isaac; Figueiredo, Roberto B.; Langdon, Terence G.

doi:10.4028/www.scientific.net/msf.941.851

Cited by 10 publications

(13 citation statements)

References 34 publications

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“…Composites with similar amount of hard quasicrystal particles could be consolidated by 10 turns of HPT using pure magnesium as matrix material but not with AZ91. It is worth noting that previous studies have shown that pure magnesium chips, pure or with the addition of alumina particles, could be consolidated after 5 turns of HPT [11,16]. On the other hand, machining chips of AZ91 were not consolidated in the same conditions [16].…”

Section: Discussionmentioning

confidence: 87%

“…It is worth noting that previous studies have shown that pure magnesium chips, pure or with the addition of alumina particles, could be consolidated after 5 turns of HPT [11,16]. On the other hand, machining chips of AZ91 were not consolidated in the same conditions [16]. Also, a recent paper showed the lack of consolidation of an AZ91-Bioactive Glass composite even after 50 turns of HPT [13].…”

Section: Discussionmentioning

confidence: 94%

“…Also, the majority of reports on consolidation of magnesium-based composites are related to commercially pure magnesium as the matrix material. Despite a report of full consolidation of a Mg-Zn-Y alloy [15], recent attempts to consolidate the AZ91 alloy did not produce sound samples [13,16]. Thus, the present paper aims to evaluate the tensile behavior of pure magnesium and a magnesium composite consolidated through HPT and to evaluate the effectiveness in consolidation of an AZ91 magnesium alloy.…”

Section: Introductionmentioning

confidence: 96%

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Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

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It is of great interest to produce magnesium-based composites through room temperature consolidation of particles using highpressure torsion. However, the lack of bonding between the particles compromises the integrity and ductility of such materials. The present work evaluates the microstructure of the composites involving pure magnesium and a magnesium alloy AZ91 with the incorporation of quasicrystal particles as a reinforcement phase. Thus, an Al-Cu-Fe icosahedral quasicrystalline alloy was produced by gas atomization and mixed with magnesium particles in a proportion of 80 % in weight of metal and 20 % of quasicrystal. The mix was processed by different number of turns of high-pressure torsion. The microstructure was observed using scanning electron microscopy and the mechanical behavior was evaluated using tensile testing. Generalized lack of bonding is observed in the AZ91 alloy matrix composite and localized lack of bonding in the pure magnesium matrix. High tensile strength has been achieved after consolidation of pure magnesium with and without quasicrystal reinforcement but all samples display limited ductility. The elongations are less than 5 % in all conditions. This is attributed to pre-existing areas with lack of bonding in the matrix, cracking of the hard particles and lack of bonding between the matrix and the reinforcement particles.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 96%

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Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

et al. 2019

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“…The effectiveness of the route depends on the nature of the materials being mixed. It has been shown that pure magnesium machining chips can be fully consolidated after 5 turns of HPT while the boundaries between the original chips of the magnesium alloy AZ91 are still visible after the same number of turns [20].…”

Section: Processingmentioning

confidence: 99%

“…The number of phases and their distribution in the microstructure depends upon the number of materials used in the mixing, the volume fraction of each material and their original size. Thus, the processing of particles of pure magnesium, without any additional phase, leads to a single phase disc after sufficient number of turns when the material is observed using optical microscopy [20]. It is, however, expected that the oxide layer of the original particles will be dispersed within the metallic matrix after consolidation.…”

Section: Microstructurementioning

confidence: 99%

Developing magnesium-based composites through high-pressure torsion

et al. 2019

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Magnesium and its alloys display interesting properties such as low density and biocompatibility but the lack of ductility and low strength compromise their performance in many applications. Fabrication of metal matrix composites may alleviate these challenges and improve overall performance. Magnesium matrix composites can be produced by cold consolidation of particles through high-pressure torsion and this paper summarizes recent findings in processing routes for the fabrication of composites, the microstructure developed, mechanical properties obtained and potential applications. It is shown that ductile materials can be mixed with magnesium by processing half samples placed side by side and hard and brittle materials can be incorporated by processing mixed particles. The distribution of phases may be controlled by the amount of rotation imposed during processing. Well-dispersed second phase particles within a continuous magnesium matrix can be obtained. Thus, it is possible to incorporate bioactive materials within a biodegradable magnesium matrix. Detailed characterization using transmission electron microscopy reveals the processing also refines the grain structure of the metallic matrix. The composites may display good ductility, improved strength and an ability to precipitate intermetallics through thermal treatment. The composites produced using high-pressure torsion have different potential applications including the development of bioactive and biodegradable biological implants.

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Inverse Hall–Petch Behaviour in an AZ91 Alloy and in an AZ91–Al₂O₃ Composite Consolidated by High‐Pressure Torsion

et al. 2019

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High-pressure torsion (HPT) is a significant procedure for achieving substantial grain refinement but it may be used also to consolidate metallic particles to form bulk samples or composites where two (or more) different phases are mixed and consolidated. Herein, the consolidation of particles of the magnesium AZ91 alloy and a composite with an AZ91 matrix combined with 1% alumina powder is investigated. The results show that it is possible to fully consolidate this alloy after a large number of turns. As a consequence of the severe plastic deformation, the grain structure is significantly refined, with average grain sizes of %116 and %98 nm in the unreinforced alloy after 20 or 50 HPT turns and %76 nm in the composite after 50 HPT turns, respectively. This grain refinement is associated with a decrease in hardness and an increase in the strain rate sensitivity due to the onset of a grain boundary diffusion-assisted creep mechanism at room temperature. The results are consistent with the theoretical prediction of a breakdown in the Hall-Petch relationship at very small grain sizes.

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Consolidation of Magnesium and Magnesium Alloy Machine Chips Using High-Pressure Torsion

Cited by 10 publications

References 34 publications

Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

Developing magnesium-based composites through high-pressure torsion

Inverse Hall–Petch Behaviour in an AZ91 Alloy and in an AZ91–Al₂O₃ Composite Consolidated by High‐Pressure Torsion

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Consolidation of Magnesium and Magnesium Alloy Machine Chips Using High-Pressure Torsion

Cited by 10 publications

References 34 publications

Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

Developing magnesium-based composites through high-pressure torsion

Inverse Hall–Petch Behaviour in an AZ91 Alloy and in an AZ91–Al2O3 Composite Consolidated by High‐Pressure Torsion

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Inverse Hall–Petch Behaviour in an AZ91 Alloy and in an AZ91–Al₂O₃ Composite Consolidated by High‐Pressure Torsion