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Process Mechanics and Surface Integrity Induced by Dry and Cryogenic Machining of AZ31B-O Magnesium Alloy

Process Mechanics and Surface Integrity Induced by Dry and Cryogenic Machining of AZ31B-O Magnesium Alloy

Keywords: Magnesium AZ31B-O; Cryogenic Machining; Process Mechanics; Surface integrity; Modelling. 1. Introduction Magnesium (Mg) alloys are emerging lightweight materials for automotive, aerospace and medical applications. The major challenge of the Mg alloys has been their unsatisfactory corrosion resistance in a saline media [1]. Past research have shown the beneficial effects of some surface integrity (SI) parameters (such as compressive residual stress, grain refinement, strong intensity of basal texture) on the improvement of the corrosion resistance of Mg alloys [2, 3]. Therefore, the control of the corrosion rate of Mg alloys via adjusting SI, seems to be an inexpensive and effective way to produce the next generation of Mg alloys components.
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In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy

In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy

The aim of the current work was to use the model proposed in [ 7 ] to describe flow stress curves reflecting various modes of deformation (1) only by slip, (2) domi- nated by tensile twinning followed by slip and (3) domi- nated by contraction twinning followed by slip. A novel continuous process of severe plastic deformation (SPD), called incremental equal channel angular pressing (I- ECAP) [ 11 , 12 ], was used in this work to produce fine- grained billets from AZ31B magnesium alloy [ 13 ]. Addi- tionally, bars processed by four passes of I-ECAP were subjected to side upsetting. Finally, tensile testing and microstructural characterisation were conducted for three types of flat samples (1) extruded (as-supplied), (2) I-ECAPed and (3) I-ECAPed followed by side upsetting. The in situ and ex situ tensile tests were performed to investigate effects of twinning on the strain hardening rate and fracture in the billets obtained by different deformation paths.
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In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy

In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy

Sonia Boczkal • Lech Olejnik Abstract The influence of twinning on the strain hard- ening rate and fracture mechanism in AZ31B magnesium alloy was studied in this work by in situ microstructural analysis during tensile testing in a chamber of scanning electron microscope. Three types of samples used in this study were obtained by (1) extrusion (as-supplied), (2) I-ECAP and (3) I-ECAP followed by side upsetting. Microstructures, textures and mechanical properties were examined after each processing step. An analytical equa- tion was used to describe flow stress curves of the samples which exhibited various modes of deformation (1) only by slip, (2) dominated by tensile twinning followed by slip and (3) dominated by contraction twinning followed by slip. It was shown that tensile twinning increases strain hardening rate, while the opposite is observed for contraction
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Prediction of the Ductility Limit of Magnesium AZ31B Alloy

Prediction of the Ductility Limit of Magnesium AZ31B Alloy

It is well known that FLDs are strongly influenced by the mechanical properties of the used sheet metal, such as plastic anisotropy and hardening parameters. Hence, two hardening laws are applied with the combined yield function (Cazacu–Barlat). In the current study, a generic Mathematica script is developed to couple the M–K approach with the reduced-order crystal plasticity model. The numerical predictions are compared with experimental results of (Kondori et al. 2018) to validate the im- plementation of this reduced-order model. Then, the ductility limit of the AZ31B magnesium alloy is analyzed. Furthermore, the effect of the activated deformation mode on the ductility limit is also investigated.
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Prediction of the ductility limit of magnesium AZ31B alloy

Prediction of the ductility limit of magnesium AZ31B alloy

It is well known that FLDs are strongly influenced by the mechanical properties of the used sheet metal, such as plastic anisotropy and hardening parameters. Hence, two hardening laws are applied with the combined yield function (Cazacu–Barlat). In the current study, a generic Mathematica script is developed to couple the M–K approach with the reduced-order crystal plasticity model. The numerical predictions are compared with experimental results of (Kondori et al. 2018) to validate the im- plementation of this reduced-order model. Then, the ductility limit of the AZ31B magnesium alloy is analyzed. Furthermore, the effect of the activated deformation mode on the ductility limit is also investigated.
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Sensitivity Analysis of Cryogenic Cooling on Machining of Magnesium Alloy AZ31B-O

Sensitivity Analysis of Cryogenic Cooling on Machining of Magnesium Alloy AZ31B-O

[6] Outeiro JC, Batista AC, Marques MJ. Residual stresses induced by dry and cryogenic cooling during machining of AZ31B magnesium alloy. Adv. Mater Research 2014; 996: 658-63. [7] Denkena B, Lucas A. Biocompatible magnesium alloys as absorbable implant materials – adjusted surface and subsurface properties by machining processes. CIRP Ann - Manuf Techn 2007; 56: 113-16. [8] Wang H, Estrin Y, Fu H, Song G, Zuberova Z. The effect of pre-

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Constitutive Modelling of AZ31B-O Magnesium Alloy for Cryogenic Machining

Constitutive Modelling of AZ31B-O Magnesium Alloy for Cryogenic Machining

* Corresponding author. Tel.: +3-324-120-7394 ; fax: +3-324-120-7320 .E-mail address: eliane.giraud@ensam.eu Abstract The success of a FE model for metal cutting process is strongly dependent on the accurate characterization of the workpiece material, under similar conditions as those found in metal cutting. In this paper, dynamic shear tests using a Gleeble machine have been performed on 4 mm thickness disks of AZ31B-O magnesium alloy, using a special designed tool. In order to include the effects of the cryogenic cooling in the material behavior, the specimens have been submitted to temperatures ranging from -25ºC to 400ºC. A Johnson-Cook constitutive model has then been identified in order to describe the flow stress in machining.
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Dislocation-driven recrystallization in AZ31B magnesium alloy imaged by quasi-in situ EBSD in annealing experiments

Dislocation-driven recrystallization in AZ31B magnesium alloy imaged by quasi-in situ EBSD in annealing experiments

Previous works on the recrystallization of deformed AZ31B alloys have reported di fferent phenomena: (i) texture evolution due to the preferential growth of grains with prismatic planes {11-20} parallel to the extrusion direction [ 15 –17 ], interpreted as a result of the anisotropy of the grain boundary mobility [ 18 ], (ii) recrystallization kinetics mainly controlled by the presence of twins and shear bands in the de- formed microstructure [ 19 –21 ], and (iii) evolution of the misorienta- tion pro files across grain boundaries [ 18 , 21 ]. Two studies have ex- plored the evolution of Mg alloys during annealing using quasi-in situ EBSD, one focusing on the relationship between twins and nucleation [ 21 ] and the other, on the e ffect of solute segregation on grain boundary mobility [ 22 ]. None of these studies, however, focused on the driving forces controlling grain boundary migration during the an- nealing of highly deformed materials, and, when analysing the evolu- tion of grain boundary misorientation, the recrystallization front was not distinguished from the grain boundaries separating two deformed or two recrystallized grains. This is problematic since recent studies on highly deformed cubic materials, based on cutting-edge techniques, have shown only little (if any) effect of the misorientation or plane normal on the grain boundary mobility [ 6 , 23–27 ], but rather concluded that the spatial variations in stored energy and the local grain boundary curvature represent the two dominant factors controlling the migration of the recrystallization front.
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Residual Stresses Induced by Dry and Cryogenic Cooling during Machining of AZ31B Magnesium Alloy

Residual Stresses Induced by Dry and Cryogenic Cooling during Machining of AZ31B Magnesium Alloy

Experimental Techniques and Parameters Orthogonal cutting tests were performed on Mg alloy AZ31B-O disks (95 mm diameter and 4 mm thickness) using uncoated cemented carbide cutting tools. The selected tool geometry according to the ISO Standard 3002/1-1982 [10] was as follows: normal rake angles (γ) equal to -6º and 5º; normal relief (flank) angle (α) equal to 6º; cutting edge radii (r n ) 35 and 70 μm. The cutting speed

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Mechanical Properties and Microstructure of AZ31B Magnesium Alloy Processed by I-ECAP

Mechanical Properties and Microstructure of AZ31B Magnesium Alloy Processed by I-ECAP

A strong texture is produced in magnesium alloys processed by ECAP. [ 13 , 26 ] Mukai et al. [ 24 ] suggested that majority of grains change their orientation in a way such that their basal planes are coincident with a shear plane. This observation was later confirmed by textural mea- surements. [ 25 ] Textural development is believed to be responsible for the decrease of yield stress and enhance- ment of ductility in ECAPed Mg alloys despite the significant grain refinement. Nevertheless, Mukai et al. [ 24 ] also showed that ECAP followed by annealing can remarkably improve room temperature ductility of AZ31 magnesium alloy. The mean grain size obtained measured about 1 lm after ECAP and 15 lm after subsequent annealing. Agnew et al. [ 25 ] reported that annealing had not changed the texture developed during ECAP. Therefore, enhancement of ductility was explained by recrystallization effects and grain growth during heat treatment.
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Al-O-N AND Al-O-B-N THIN FILMS APPLIED ON Si-O-C FIBERS

Al-O-N AND Al-O-B-N THIN FILMS APPLIED ON Si-O-C FIBERS

presented in table 1. These last observations may be explained by a de-mixing process in gradually taking place in the coating as the nitridation temperature was increased, leading to the formation of Al 2 O 3 while liberating nitrogen. Conversely, in the case of the Al-O-N- B coatings, such phenomena were not observed (table 2). Finally, high resolution TEM showed that both thin films were homogeneous, amorphous (no ring patterns of selected- area electron-diffraction were observed) and adhere to the fibers.

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Thermodynamic Modeling of Aluminum-Magnesium-Rare Eearth Systems

Thermodynamic Modeling of Aluminum-Magnesium-Rare Eearth Systems

 1.738 g/cm 3 ). Magnesium is 35% lighter than aluminum (  2.698 g/cm 3 ), 62% lighter than titanium (  4.540 g/cm 3 ), and 78% lighter than iron (  7.874 g/cm 3 ). Its high strength-to-weight ratio makes it even more attractive than steel in many applications. Due to limited fossil fuel resources and environmental issues, there is a compelling tendency in the automotive industry to make cars lighter to reduce fuel consumption and greenhouse gas emission. World consumption of magnesium alloys in the automotive industry increased 15% per year for more than a decade (Liu, 2008). Moreover, magnesium is easily recycled; it also has high thermal conductivity, good electromagnetic shielding characteristics, high damping characteristics, good machinability, high dimensional stability and favorable environmental properties (Froes et al., 1998). These advantageous properties make Mg alloys an excellent choice for a number of applications, like computer housings and cell phone cases. Magnesium – aluminum – based alloys are widely used because of their low density, high strength-to-weight ratio, specific rigidity, satisfactory salt- spray corrosion resistance and good ductility. Although magnesium alloys offer light weight, high stiffness, excellent machinability and the best alternative for weight reduction, their use for engineering applications is restricted to a few structural parts in the automotive and other transport industries due to their poor creep resistance at elevated temperatures (above 150 ° C), which has made them inadequate for engine blocks or powertrain applications. Automatic transmission cases can operate up to 175 ° C, engine blocks up to 200 ° C, and engine pistons up to 300 ° C (Yang et al., 2008). Adding rare earth (RE) elements in Mg–Al alloys (i.e. AE41, AE42 alloys) may improve the creep resistance (Pettersen et al., 1996) and strength at elevated temperatures due to the precipitation of the intermetallic phases (eg. Al 11 RE 3 ) and suppression of
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Effect of vitamin B6 supplementation, in combination with magnesium, on severe stress and magnesium status: secondary analysis from an RCT

Effect of vitamin B6 supplementation, in combination with magnesium, on severe stress and magnesium status: secondary analysis from an RCT

3 Unité de Nutrition Humaine, INRA, Université Clermont Auvergne, Clermont-Ferrand, France Abstract Introduction: Evidence from a recent randomised controlled trial 1 suggests that in severely stressed subjects with low magnesemia, supplementation with magnesium (Mg) in combination with vitamin B6 (B6) provides greater benefits than Mg alone. B6 was reported to facilitate Mg absorption and its cellular uptake and to exert synergistic effect with Mg. The current secondary analysis explored the relationship between Mg-B6 combination and erythrocyte Mg concentration, used as a biomarker of body Mg status. Material and Methods: An 8-week, Phase IV, controlled, single-blinded, parallel-group trial (EudraCT Number 2015-003749-24) stra- tified by sex was conducted in adults (n = 264) with a Depression Anxiety Stress Scales - stress subscale score (DASS-42SS) > 18 and serum Mg of 0.5 –0.85mmol/L, randomised 1:1 to daily oral Mg-B6 (Magne B6®, Mg 300 mg; B6 30mg) or oral Mg alone (Magnespasmyl®, Mg 300mg). Outcomes were stress score, serum Mg (mmol/L), erythrocytes Mg (mmol/L), and serum B6 (nmol/L) from baseline to Week4 and Week8. Data are given as mean(SD) values.
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Theoretical isotopic fractionation of magnesium between chlorophylls

Theoretical isotopic fractionation of magnesium between chlorophylls

Δ E rel is a correction due to relativistic effects for metal centers, and ΔE geom is a correction due to geometry relax- ation for H 2 O during the formation of the clusters. The magnitude of “−ΔE zp + ΔE rel + ΔE geom ” was reported to be negligibly small (a few kcal/mol) 18 , and hence these corrections were not included in our calculation. The calculated value of ΔH° hyd is shown in Table  1 . The hydration enthalpy of metal cations has been determined by

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Epidemiology of Low Magnesium Intake and Status

Epidemiology of Low Magnesium Intake and Status

Faculty of Medicine, University in Belgrade, Institute of Pharmacology, Clinical Pharmacology and Toxicology, Belgrade, Serbia. 17:35 - 17:45[r]

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3D molding simulation of semi-solid magnesium alloys

3D molding simulation of semi-solid magnesium alloys

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB. READ THESE T[r]

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Impregnation of magnesium oxychloride cement with sulfur

Impregnation of magnesium oxychloride cement with sulfur

1) Impregnation of magnesium oxychloride cement with sulfur increases microhardness and modulus of elasticity. The decrease in these mechanical properties on exposure to water is l[r]

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Structuration of Magnesium Surface by Acoustic Cavitation

Structuration of Magnesium Surface by Acoustic Cavitation

This study focuses on the sonication effect on extended magnesium surfaces at low (20 kHz), intermediate (100-200 kHz) and high (1 MHz) frequency ultrasound in dilute oxalic acid. Sonication effects are followed by means of SEM, 3D image reconstruction, wetting behavior analysis, mass spectrometer and ICP-AES. Investigations revealed a strong ultrasonic frequency dependency of the effects generated at the metallic samples. 20 kHz leads to strong erosion and transformation of the surface with the formation of large pits, holes and channels (Fig. 1.a). 1 MHz sonication results in a smooth surface devoid of pitting. By contrast, golf- ball like extended craters and new spherical micrometric structures can be observed for intermediate frequencies (Fig. 1.b and c.). Such crater structuring is characterized by a high wetting behavior and a roughness of 170 nm measured by a 3D reconstruction program. The investigations showed that such architectures result from the ultrasonically controlled dissolution of the Mg surface. Heterogeneous nucleation provided by the creation of defects by ultrasound and the release of H 2 gas are supposed to be at the origin of the crater formation.
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Impact of magnesium supplementation, in combination with vitamin B6, on stress and magnesium status: secondary data from a randomized controlled trial

Impact of magnesium supplementation, in combination with vitamin B6, on stress and magnesium status: secondary data from a randomized controlled trial

Correspondence : Lionel Noah Global Medical Nutritionals, Consumer Healthcare, Sanofi, 82 Avenue Raspail, 94255, Gentilly Cedex, France. <Lionel.Noah@sanofi.com> Abstract. Background: Primary findings from a recent study reported that magnesium supplementation significantly reduced stress in severely stressed subjects with low magnesemia, and additional vitamin B6 enhanced this effect. The mechanism by which combining magnesium and vitamin B6 leads to reduced stress in these subjects remains to be elucidated. This secondary analysis investigated the impact of magnesium and vitamin B6 supplementa- tion and perceived stress on erythrocyte magnesium levels, as a marker of body magnesium status. Methods: This was a secondary analysis from an 8-week randomized controlled trial comparing oral magnesium (300 mg) and magne- sium-vitamin B6 (300 mg + 30 mg) supplementation. Stress level and erythro- cyte magnesium level at baseline, and change in erythrocyte magnesium and serum vitamin B6 levels at weeks 4 and 8, were analyzed. Results: Overall, 264 subjects were randomized to treatment and had evaluable Depression Anxiety Stress Scale scores (132 in each treatment arm). At baseline, stress scores, and mean serum magnesium, erythrocyte magnesium, and serum vitamin B6 concentrations were similar between arms. Although not significant between groups, a significant increase over time in erythrocyte magnesium levels was observed in the subgroup of subjects with low baseline erythrocyte magnesium levels (<1.6 mmol/L) following treatment with magnesium and magnesium- vitamin B6 (week 4:0.21 mmol/L [95% confidence interval (CI), 0.10 to 0.31], p = 0.0003; and 0.13 mmol/L [95% CI, 0.02 to 0.23], p = 0.0233, respectively). Change from baseline in circulating vitamin B6 levels at weeks 4 and 8 in the magnesium-vitamin B6 supplemented group (314.96 nmol/L [95%CI, 294.61 to 335.31]) was significantly different (p < 0.0001) compared with the magnesium supplemented group (-0.39 nmol/L [95% CI, -20.73 to 19.94]). Conclusion: Magnesium alone and magnesium-vitamin B6 provided statistically significant increases in erythrocyte magnesium in subjects with low magnesium status
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Mold Filling Simulation of Semi-Solid Magnesium Alloys

Mold Filling Simulation of Semi-Solid Magnesium Alloys

Mold Filling Simulation of Semi-Solid Magnesium Alloys Ilinca, Florin; Hétu, Jean-Francois; Ajersch, Frank; Moisan, Jean-Francois https://publications-cnrc.canada.ca/fra/droits L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

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