Fatigue properties of magnesium alloy AZ91 processed by severe plastic deformation

Fintová, Stanislava; Kunz, Ludvík

doi:10.1016/j.jmbbm.2014.11.019

Cited by 60 publications

(31 citation statements)

References 25 publications

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“…However, at the same time, increased surface roughness can dwindle the fatigue behavior by forming potential sites of stress concentration [43]. Moreover, the surface grain refinement can play a positive role in delaying crack initiation or change the crack initiation mechanism and, thus, promote fatigue strength enhancement [17,42]. Therefore, the contribution of all these parameters is expected to enhance the fatigue strength of the SSP treated material, although further experiments are required to accurately estimate these effects.…”

Section: Discussionmentioning

confidence: 99%

Effects of nanofeatures induced by severe shot peening (SSP) on mechanical, corrosion and cytocompatibility properties of magnesium alloy AZ31

et al. 2018

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The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Considering the sensitivity of both fatigue strength and corrosion rate to the surface characteristics of the material, apposite surface treatments could address these challenges. As a low cost and versatile severe plastic deformation technique aimed at inducing surface grain refinement, severe shot peening has been effective in enhancing mechanical properties and promoting cellular interactions on non-degradable biocompatible metallic materials. Herein, we treated the surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of surface grain refinement to enhance its functionality in a biological environment. The AZ31 samples were studied in terms of a wide variety of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of surface grain structure and surface morphology were investigated using optical as well as scanning and transmission electron microscopy. Surface roughness, wettability and chemical composition, as well as in depth-microhardness and residual stress distribution, and corrosion resistance were investigated. Successive light surface grinding was used after severe shot peening to eliminate the effect of surface roughness and separately investigate the influence of grain refinement alone. Cytocompatibility tests with osteoblasts (or bone forming cells) were performed using sample extracts. Results revealed for the first time that severe shot peening can significantly enhance mechanical properties without causing adverse effects to the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved by severe shot peening; nevertheless, slight grinding of the rough surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used.

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Section: Discussionmentioning

confidence: 99%

Effects of nanofeatures induced by severe shot peening (SSP) on mechanical, corrosion and cytocompatibility properties of magnesium alloy AZ31

et al. 2018

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“…The microstructural stability loss can occur during a thermal exposition 6,7 or mechanical loading (predominantly fatigue loading). 8,9 The instability can be manifested as grain coarsening connected with a decrease in the mechanical properties, which can be lower than the properties of an unprocessed, virgin material.…”

Section: Introductionmentioning

confidence: 99%

Microstructural changes of ECAP-processed magnesium alloy AZ91 during cyclic loading at different stress-amplitude levels

Štěpánek¹,

Pantělejev²,

Man³

et al. 2018

Mater. Tehnol.

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Microstructural changes of magnesium alloy AZ91 after fatigue loading in the EX-ECAP state were evaluated using EBSD. It was found that both the number fraction of low-angle boundaries and parameter KAM decreased after the testing at a stress amplitude of 160 MPa but started to increase with the increasing stress amplitude. This behaviour can be explained with a mutual influence of dislocation accumulation (which is stronger with a higher stress amplitude) and dynamic softening (which is weaker with a decreasing number of cycles/cycles to failure). The average grain size remained almost unchanged except at a stress amplitude of 180 MPa, which could have been caused by certain conditions allowing an ideal development of both mentioned phenomena. Keywords: magnesium alloy, ECAP, EBSD, fatigue loading V pri~ujo~em~lanku avtorji opisujejo ovrednotenje mikrostrukturnih sprememb magnezijeve zlitine AZ91 z EBSD metodo zaradi utrujanja po procesiranju z ECAP-postopkom. Ugotovili so, da se tako dele`malo kotnih mej kot tudi parameter razlik v kristalografski orientaciji kristalnih zrn (KAM; angl.: Kernel Average Misorientation) zni`ujeta po testiranju pri napetostni amplitudi toda pri~neta nara{~ati z nara{~ajo~o napetostno amplitudo. To obna{anje si je mo~razlo`iti z isto~asnim vplivom kopi~enja dislokacij, (ki je intenzivnej{e pri vi{jih napetostnih amplitudah) in dinami~nim meh~anjem, (ki je manj{e pri manj{em razmerju med dejanskim {tevilom ciklov in {tevilom ciklov do poru{itve). Povpre~na velikost kristalnih zrn je ostala skoraj nespremenjena pri napetostni amplitudi 180 MPa, kar je lahko posledica specifi~nih pogojev, ki omogo~ajo idealen potek obeh omenjeni pojavov (mehanizmov). Klju~ne besede: zlitina na osnovi magnezija, ekstremno mo~na plasti~na deformacija (SPD) dose`ena z enokanalnim pravokotnim procesiranjem (ECAP), preiskovalna metoda na osnovi uklona povratno sipanih elektronov (EBSD), utrujanje oz. dinami~no (cikli~no) obremenjevanje

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“…SPD introduces substantial changes in the grain structure including, but not limited to the texture, grain shape, grain size, subgrain dislocation structure, dislocation densities, deformation twinning, and grain boundary misorientations . These microstructural changes impact the mechanical properties, and aspects like strengthening effects, plastic anisotropy, ductility, fatigue, fracture behavior, creep, and conductivity have been probed . In many cases, the effects are profound, and intense studies on processing‐microstructure‐property relationships in SPD materials have been carried out for over the past three decades …”

Section: Introductionmentioning

confidence: 99%

Effect of Grain Shape on Texture Formation during Severe Plastic Deformation of Pure Copper

2017

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In this study, the authors use a combination of electron backscattered diffraction and polycrystal plasticity modeling to study the effect of grain shape on texture development in high pressure torsion and high pressure double torsion in high purity Cu. With varying applied pressures and after a large amount of strain corresponding to two to four turns, the average aspect ratios of the grains has changed from being elongated under higher pressures to nearly equiaxed for lower pressures, while keeping the average grain size similar among all samples analyzed. Polycrystal modeling is used to help isolating the deformation effect from the grain shape effect. The authors show that grains with elongated shapes form shear textures with a predominant C component, whereas those with largely equiaxed grains possess conventional shear textures.

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Fatigue properties of magnesium alloy AZ91 processed by severe plastic deformation

Cited by 60 publications

References 25 publications

Effects of nanofeatures induced by severe shot peening (SSP) on mechanical, corrosion and cytocompatibility properties of magnesium alloy AZ31

Effects of nanofeatures induced by severe shot peening (SSP) on mechanical, corrosion and cytocompatibility properties of magnesium alloy AZ31

Microstructural changes of ECAP-processed magnesium alloy AZ91 during cyclic loading at different stress-amplitude levels

Effect of Grain Shape on Texture Formation during Severe Plastic Deformation of Pure Copper

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