Microstructural characterization of the Mg–Al alloy AM50 produced by a newly developed rheo-casting process

Esmaily, Mohsen; Shahabi-Navid, Mehrdad; Mortazavi, N.; Svensson, Jan‐Erik; Halvarsson, Mats; Wessén, Magnus; Jarfors, Anders E. W.; Johansson, Lars

doi:10.1016/j.matchar.2014.06.001

Cited by 36 publications

(41 citation statements)

References 33 publications

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“…The role of casting technology on the area fraction of intermetallic phase particles is discussed elsewhere. 31 From mechanical properties point of view, while considering the α-Mg grain size and intermetallic characteristics, requirements are contradictory. For instance, fine grains are beneficial for fatigue, but coarse grain enhances creep resistance, see Refs.…”

Section: Discussionmentioning

confidence: 99%

“…Further, since the semi-solid slurry contains a large content of solid phase (typically around 30-40%), the solidification shrinkage will be smaller. 31 Although the deteriorating influence of porosity on the mechanical properties of the Mg alloys is well-known, the effect of porosity on the atmospheric corrosion behavior of Mg-Al alloys is not known. Thus, further research on the relationship between casting porosity and the corrosion of Mg-Al alloys is warranted.…”

Section: Discussionmentioning

confidence: 99%

“…The strategy to quantify all the microstructural features such as fraction of pore, inter-dendritic regions, intermetallic phase particles, and aspect ratio of α-Mg grains is provided in. 31 The aspect ratio was defined as F = 4 πA/P 2 , where A is the area and P is the peripheral length of a grain.…”

Section: Methodsmentioning

confidence: 99%

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Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Esmaily

Mortazavi

Shahabi-Navid

et al. 2014

J. Electrochem. Soc.

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The corrosion behavior of magnesium-aluminum (Mg-Al) alloy AM50 produced by a rheocasting (RC) technique was examined in the presence and absence of CO 2 at three temperatures −4, 4 and 22 • C. The slurry preparation in the RC material was performed with the newly developed RheoMetal process. For reference, 99.97% Mg was included in the corrosion exposures. The influence of the microstructure on the atmospheric corrosion of alloy AM50 produced by RC and high pressure die casting (HPDC) was investigated. The RC AM50 alloy showed better corrosion resistance than HPDC AM50 in all the exposure environments studied. For both materials, there was a strong positive correlation between temperature and the atmospheric corrosion rate. The superior atmospheric corrosion behavior of RC AM50 compared to HPDC AM50 is carefully discussed in relation to differences in the as-cast microstructure. This study demonstrates that producing the alloy AM50 by this type of RC technique opens the door to Mg-Al alloys as a promising candidate for various applications where corrosion resistance is of importance. Magnesium-aluminum (Mg-Al) alloys are being employed in the automotive and many other engineering sectors owing to their high specific strength, high specific stiffness, good castability and recycleability, excellent machinability and abundant resources.1-4 Thus, they offer several advantages from the weight reduction and energy savings points of view. However, the more widespread use of MgAl alloys is limited by their low corrosion resistance and poor high temperature mechanical properties. [5][6][7][8] The corrosion properties of MgAl alloys have therefore attracted scientific attention. Currently, the majority of Mg-Al cast components are produced by conventional high-pressure die casting (HPDC). One of the main problems of thickwalled Mg-Al components made by HPDC is the relatively high fraction of porosity caused by the turbulent die filling. The pores function as local stress concentrators and can severely degrade mechanical properties and porosity also interferes with the heat-treatment of cast components. 9,10 Semi-solid casting is an alternative manufacturing technique that can be used to produce castings with a high level of complexity. In this process, a semi solid slurry is used, which shows non-turbulent or thixotropic flow behavior. Semi-solid cast alloys offer some advantages over their HPDC counterparts. For instance, porosity is lower due to laminar mould-filling and lower solidification shrinkage. 11,12Thixo-forming and rheocasting (RC) are the main semi-solid manufacturing processes. In thixo-forming, a near-net shape forming process is achieved using a partially melted, non-dendritic alloy slug. 12In contrast, RC involves preparation of a semi-solid slurry from the liquid alloy by cooling. In the RheoMetal process (also called the RSF process or the Rapid S process) cooling is performed by using an enthalphy exchange material (EEM) attached to a stirrer. 13 Thus, the metal is cooled internally which eliminates t...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Esmaily

Mortazavi

Shahabi-Navid

et al. 2014

J. Electrochem. Soc.

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“…Many kinds of alloying elements have been studied including Zn, manganese (Mn) and aluminum (Al) [8][9][10]. Among these elements, Zn has great application prospects, since it is an essential trace element in a physiological environment, and can participate in bone metabolism and growth [11].…”

Section: Introductionmentioning

confidence: 99%

Influence of Alloying Treatment and Rapid Solidification on the Degradation Behavior and Mechanical Properties of Mg

Chen

Wang

et al. 2016

Metals

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Magnesium (Mg) has drawn increasing attention as a tissue engineering material. However, there have been very few studies of laser-melted Mg-Zn alloys. In this study, four binary Mg-xZn (x = 2, 4, 6 and 8 wt. %) alloys were fabricated by laser melting. The influence of zinc (Zn) content and technique on the degradation behavior and mechanical properties of Mg were discussed. Results revealed that Mg-xZn alloys consisted of an α-Mg matrix and MgZn phases, which dispersed at the grain boundaries. In addition, the MgZn phase increased with the increase in Zn content. The laser-melted alloy had fine homogenous grains, with an average grain size of approximately 15 µm. Grain growth was effectively inhibited due to the precipitation of the MgZn phase and rapid solidification. Grain refinement consequently slowed down the degradation rate, with Zn content increasing to 6 wt. %. However, a further increase of Zn content accelerated the degradation rate due to the galvanic couple effect between α-Mg and MgZn. Moreover, the mechanical properties were improved due to the grain refinement and reinforcement of the MgZn phase.

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“…However, Mg alloys are sensitive towards corrosion and exhibit the lowest corrosion potentials among the engineering metals. [1][2][3][4] Also, Mg and Mg-Al alloys exhibit high corrosion rates when immersed in NaCl (aq) solution, corrosion being more severe compared to other engineering alloys, including carbon steel. Nevertheless, Mg alloys exhibit somewhat better corrosion properties than steels under atmospheric conditions.…”

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confidence: 99%

The Influence of SO₂on the Corrosion of Mg and Mg-Al Alloys

Esmaily

Blücher

Lindström

et al. 2015

J. Electrochem. Soc.

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The SO 2 -induced atmospheric corrosion of some magnesium-aluminum (Mg-Al) alloys, including Mg alloy AZ91D, and commercially pure Mg (CP Mg) was investigated using well-controlled laboratory exposures and included real-time measurements of SO 2 deposition. The influence of SO 2 concentration, alloy composition, humidity, and ppb level additions of O 3 or NO 2 on the rate of SO 2 deposition was investigated. SO 2 accelerates the corrosion of Mg and Mg alloys causing localized corrosion, MgSO 3 6H 2 O being the dominant corrosion product. At 60% RH, traces of O 3 or NO 2 strongly increased both the SO 2 deposition and the corrosion rate. The rate of SO 2 deposition was strongly dependent on humidity; at 70% RH and higher the SO 2 deposition rate was very rapid and constant in time while it was transient below 50% RH. At 60% RH, a change from transient to rapid, steady-state, SO 2 deposition occurred. The sudden activation is explained by the onset of electrochemical corrosion. The activation behavior was shown to depend on SO 2 concentration, the thickness of the surface film and by the presence of ambient O 2 . © The Author Magnesium-aluminum (Mg-Al) alloys are widely used as structural materials in many engineering sectors as a result of their good castability and good mechanical properties at room temperature. Due to their low weight/strength ratio, these types of Mg alloys have found widespread applications; from portable microelectronics to automobiles and aircraft. However, Mg alloys are sensitive towards corrosion and exhibit the lowest corrosion potentials among the engineering metals.1-4 Also, Mg and Mg-Al alloys exhibit high corrosion rates when immersed in NaCl (aq) solution, corrosion being more severe compared to other engineering alloys, including carbon steel. Nevertheless, Mg alloys exhibit somewhat better corrosion properties than steels under atmospheric conditions. [5][6][7][8] The causes behind the relatively slow corrosion of Mg-Al alloys in the atmosphere are still not fully clear.Because Mg-Al alloys are often used in atmospheric conditions, a better understanding of the atmospheric corrosion properties is of importance. A large number of parameters affect the atmospheric corrosion process of Mg-Al alloys. Therefore, systematic studies are required to clarify their role on the corrosion. There have been extensive researches on the atmospheric corrosion behavior of Mg alloys using field studies that correlate corrosion rate to selected environmental parameters. [9][10][11][12][13][14][15][16][17][18][19] The variability and complexity of the outdoor atmosphere constitute a major problem when trying to correlate the corrosion rate of a metal to the concentration of, e.g., a particular trace gas in the environment. Laboratory studies under controlled conditions provide the opportunity to study the effect of a specific parameter and/or the synergic effects of atmospheric variable on the corrosion of metallic materials. For example, laboratory investigations have shown that carbon dioxide (CO 2 ...

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Microstructural characterization of the Mg–Al alloy AM50 produced by a newly developed rheo-casting process

Cited by 36 publications

References 33 publications

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Influence of Alloying Treatment and Rapid Solidification on the Degradation Behavior and Mechanical Properties of Mg

The Influence of SO₂on the Corrosion of Mg and Mg-Al Alloys

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Microstructural characterization of the Mg–Al alloy AM50 produced by a newly developed rheo-casting process

Cited by 36 publications

References 33 publications

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Influence of Alloying Treatment and Rapid Solidification on the Degradation Behavior and Mechanical Properties of Mg

The Influence of SO2on the Corrosion of Mg and Mg-Al Alloys

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Product

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The Influence of SO₂on the Corrosion of Mg and Mg-Al Alloys