Enhanced Corrosion Resistance of AZ91 Alloy Produced by Semisolid Metal Processing

Mingo, B.; Arrabal, R.; Mohedano, M.; Pardo, Á.; Matykina, E.; Rivas, A.

doi:10.1149/2.0521504jes

Cited by 25 publications

(20 citation statements)

References 48 publications

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“…It has been shown that for a AZ91 alloy produced by rheocasting, the early stages of corrosion were located at the centre of α-Mg globules and more importantly at α-Mg/β-phase interfaces due to galvanic coupling. [41] Regarding galvanic coupling, corrosion around MnAl 2 inclusions is also reported to play a role in Mg-Al alloys. [60] Czerwinski et al [61] investigated the existence of chemical segregation within the primary grains.…”

Section: Resultsmentioning

confidence: 99%

“…[ 22,40 ] The corrosion resistance in a saline aqueous solution of a rheocast AZ91 alloy was ∼15 times higher in comparison with the same alloy produced via gravity cast. [ 41 ]…”

Section: Introductionmentioning

confidence: 99%

“…[22,40] The corrosion resistance in a saline aqueous solution of a rheocast AZ91 alloy was ∼15 times higher in comparison with the same alloy produced via gravity cast. [41] It was proposed that the best corrosion resistance observed for semisolid cast specimens is due to a continuous and small meshed Mg 17 Al 12 network, a homogeneous and small α-Mg grain size, a minimal extent of Al and Zn segregations and higher amount of β-phase in comparison to other production process. [42,43] Mathieu et al [43] investigated the corrosion behaviour of high-pressure die-cast and thixocast AZ91D alloys.…”

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confidence: 99%

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Thixomolded AZ91D and MRI153M magnesium alloys and their enhanced corrosion resistance

Buzolin

Volovitch

Maltseva

et al. 2020

Materials & Corrosion

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AZ91D and MRI153M alloys were produced by thixomolding. Their corrosion resistance is significantly higher than that of similar materials produced by ingot or die‐casting. A corrosion rate smaller than 0.2 mm/year in 5 wt% NaCl solution is measured for the thixomolded AZ91D alloy. The corrosion behaviour was evaluated using immersion tests, electrochemical impedance spectroscopy, hydrogen evolution, glow discharge optical emission spectroscopy, and atomic emission spectroelectrochemistry. A bimodal microstructure is observed for both alloys, with the presence of coarse primary α‐Mg grains, fine secondary α‐Mg grains, β‐phase, and other phases with a minor volume fraction. The amount of coarse primary α‐Mg is significantly higher for the AZ91D compared with the MRI153M. The network of β‐phase around the fine secondary α‐Mg grains is better established in the thixomolded AZ91D alloy. A combination of several factors such as the ratio of primary to secondary α‐Mg grains, localised corrosion or barrier effect due to other phases, as well as regions of preferential dissolution of the α‐Mg due to chemical segregation, are thought to be responsible for the high corrosion resistance exhibited by the thixomolded AZ91D and MRI153M.

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Section: Resultsmentioning

confidence: 99%

“…[ 22,40 ] The corrosion resistance in a saline aqueous solution of a rheocast AZ91 alloy was ∼15 times higher in comparison with the same alloy produced via gravity cast. [ 41 ]…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Thixomolded AZ91D and MRI153M magnesium alloys and their enhanced corrosion resistance

Buzolin

Volovitch

Maltseva

et al. 2020

Materials & Corrosion

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“…It may be noted that the α-Mg grain morphology in the studied RC AZ91D differs from the globular α-Mg morphology (with high aspect ratio) observed in the microstructure of a RC AZ91 material where the slurry was made by electromagnetic stirring. 38 EBSD mapping provided an opportunity to evaluate the low angle grain boundaries (LAGBs), boundaries with a misorientation < 15…”

Section: Resultsmentioning

confidence: 99%

“…However, there is limited knowledge on the microstructure and atmospheric corrosion behavior of the alloy RC AZ91D. Very recently, Mingo et al 38 studied the corrosion resistance of alloy AZ91 produced by RC process using electromagnetic stirring in 3.5 wt% NaCl at pH 6.5. They compared the corrosion results of the RC AZ91D with those of the alloy produced by gravity casting (GC) and reported a better corrosion resistance of RC AZ91D.…”

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confidence: 99%

Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by a Semi-Solid Casting Technique: The Influence of Microstructure

Esmaily

Mortazavi

Svensson

et al. 2015

J. Electrochem. Soc.

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The atmospheric corrosion behavior of alloy AZ91D produced by a semi-solid metal (SSM) technique and by conventional high pressure die casting (HPDC) was investigated for up to 1176 hours in the laboratory. Alloy AZ91D in the SSM state was fabricated using a rheocasting (RC) technique in which the slurry was prepared by the RheoMetal process. Exposures were performed in 95% RH air at 22 and 4 • C. The RC alloy AZ91D exhibited significantly better corrosion resistance than the HPDC material at two temperatures studied. The effect of casting technology on corrosion is explained in terms of the microstructural differences between the materials. For example, the larger number density of cathodic β phase particles in the HPDC material initially causes relatively rapid corrosion compared to the RC material. During later stages of corrosion, the more network-like β phase particles in the RC alloy act as a corrosion barrier, further improving the relative corrosion resistance of the RC material. Conventional magnesium-aluminum (Mg-Al) alloys, i.e., AZ91D, AM50A and AM60B, offer an exceptional combination of ambient temperature strength and ductility, and good die-castability.1-4 Cast components made of Mg-Al alloys are usually cast by conventional high pressure die casting (HPDC). Despite its advantages over many other casting techniques for producing cast Mg-Al components, there are some inherent problems associated with HPDC. For example, there is a tendency for hot tearing during HPDC due to a relatively wide freezing range and a low solidus temperature. Also, a relatively high fraction of trapped air porosity may form during the turbulent die filling, especially in thick-walled components. Additionally, insufficient resistance to atmospheric and aqueous corrosion sometimes limits Mg-Al alloys applications in the fields of automobiles, aerospace, electronics, etc.5-8 During the past two decades, there have been extensive efforts to increase the corrosion resistance of Mg-Al alloys. Much of the effort has concentrated on the use of various coating systems such as chemical conversion coatings, anodizing, gas-phase deposition processes electro-or electro-less plating, and organic coating. [9][10][11][12][13][14][15] Lowering the impurity levels, alloying, rare earth additions, and heattreatment have also been explored to increase the corrosion resistance of these alloys. [16][17][18][19][20] Alternative casting processes are being developed to resolve the mentioned problems and meet the requirements of future applications of Mg-Al alloys. Semi-solid metal (SSM) processing is a promising manufacturing route capable of producing castings with a high level of complexity. 21,22 The main advantage of SSM processing, compared to the conventional casting processes, is the possibility to have a laminar flow of metal during mold filling.23 This is a consequence of the higher viscosity of the semi-solid material, and it reduces air entrapment compared to die-casting. This results in components with enhanced microstructural proper...

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Biodegradable AZ91 magnesium alloy/sirolimus/poly D, L‐lactic‐co‐glycolic acid‐based substrate for cardiovascular device application

Mohanta,

Ramdhun,

Thirugnanam

et al. 2023

J Biomed Mater Res

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Biodegradable drug‐eluting stents (DESs) are gaining importance owing to their attractive features, such as complete drug release to the target site. Magnesium (Mg) alloys are promising materials for future biodegradable DESs. However, there are few explorations using biodegradable Mg for cardiovascular stent application. In this present study, sirolimus‐loaded poly D, L‐lactic‐co‐glycolic acid (PLGA)‐coated/ sirolimus‐fixed/AZ91 Mg alloy‐based substrate was developed via a layer‐by‐layer approach for cardiovascular stent application. The AZ91 Mg alloy was prepared through the squeeze casting technique. The casted AZ91 Mg alloy (Mg) was alkali‐treated to provide macroporous networks to hold the sirolimus and PLGA layers. The systematic characterization was investigated via electrochemical, optical, physicochemical, and in‐vitro biological characteristics. The presence of the Mg17Al12 phase in the Mg sample was found in the x‐ray diffraction system (XRD) spectrum which influences the corrosion behavior of the developed substrate. The alkali treatment increases the substrate's hydrophilicity which was confirmed through static contact angle measurement. The anti‐corrosion characteristic of casted‐AZ91 Mg alloy (Mg) was slightly less than the sirolimus‐loaded PLGA‐coated alkali‐treated AZ91 Mg alloy (Mg/Na/S/P) substrate. However, dissolution rates for both substrates were found to be controlled at cell culture conditions. Radiographic densities of AZ91 Mg alloy substrates (Mg, Mg/Na, and Mg/Na/S/P) were measured to be 0.795 ± 0.015, 0.742 ± 0.01, and 0.712 ± 0.017, respectively. The star‐shaped structure of 12% sirolimus/PLGA ensures the bioavailability of the drugs. Sirolimus release kinetic was fitted up to 80% with the “Higuchi model” for Mg samples, whereas Mg/Na/S/P showed 45% fitting with a zero‐order mechanism. The Mg/Na/S/P substrate showed a 70% antithrombotic effect compared to control. Further, alkali treatment enhances the antibacterial characteristic of AZ91 Mg alloy. Also, the alkali‐treated sirolimus‐loaded substrates (Mg/Na/S and Mg/Na/S/P) inhibit the valvular interstitial cell's growth significantly in in‐vitro. Hence, the results imply that sirolimus‐loaded PLGA‐coated AZ91 Mg alloy‐based substrate can be a potential candidate for cardiovascular stent application.

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Enhanced Corrosion Resistance of AZ91 Alloy Produced by Semisolid Metal Processing

Cited by 25 publications

References 48 publications

Thixomolded AZ91D and MRI153M magnesium alloys and their enhanced corrosion resistance

Thixomolded AZ91D and MRI153M magnesium alloys and their enhanced corrosion resistance

Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by a Semi-Solid Casting Technique: The Influence of Microstructure

Biodegradable AZ91 magnesium alloy/sirolimus/poly D, L‐lactic‐co‐glycolic acid‐based substrate for cardiovascular device application

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