Inclusions in magnesium and its alloys: a review

Abstract

High volume application of lightweight materials is the key to improving fuel efficiency and vehicle performance, and decreasing exhaust emissions to address environmental concerns. Currently, magnesium alloys, which are the lightest structural materials, represent only y0?3% of an automobile weight. One of the most important parameters in controlling the properties of magnesium and its alloys is melt cleanliness, manifested mainly in inclusions. The presence of such inclusions will strongly influence the mechanical properties and corrosion resistance of structural components. This paper gives an overview of the current state of knowledge pertaining to magnesium melt cleanliness. It describes the nature and origin of the inclusions, the methods for assessing the cleanliness of magnesium, the methods used to control inclusions in the melt and the relationship between melt cleanliness and the properties of magnesium castings.

Melt Protection of Mg-Al Based Alloys

“…MgCl 2 can be used in Mg alloys containing Al, Zn and Mn alloying elements such as AZ91D, AM60, AM50 and AZ31 representing the majority of commercial Mg alloys. Flux entrapment, release of corrosive gas and melt losses are the major causes for the shift from flux to gas protective atmospheres [49].…”

“…Mirak et al [16] summarised the significant findings on protective gases in stagnant melts held isothermally under a mixture of a protective gas (e.g., SF 6 , SO 2 or 1,1,1,2-tetrafluoroethane (HFC-134a)) and a carrier gas (e.g., dry air or N 2 ), based on characterisation of the reaction layer formed on the melt surface by the use of various techniques, including SEM, TEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) and assessment of the corresponding oxidation behaviour. Mg melt protection in the context of the nature, origin and control of inclusions with regard to reactions with air, fluxes and protective gases during melt treatment, casting and alloying was later reviewed by Lun et al [49].…”

“…The reaction products between Mg melt and SF 6 , HFC-134a and FK are MgO and MgF 2 . Mg melt can react with SO 2 to form MgSO 4 , MgO or MgS [49].…”

“…The use of solid CO 2 can generate toxic CO [51]. BF 3 is not a GHG, however, is highly toxic, expensive and require the use of special storage conditions [49]. It should be noted that nowadays the use of SO 2 gas for Mg melt protection might require a SO 2 scrubber system (i.e., flue gas desulfurization (FGD) technology to comply with the environmental legislation) as well as additional costs associated with corrosion of equipment handling dilute SO 2 .…”

Influence of gas mixture during N+ ion modification under plasma conditions on surface structure and mechanical properties of Al–Zn alloys

“…Decrease in vehicle weight, leading as a consequence to limited energy consumption, is one of the most important challenges in the field of modern transport [1,2]. Among metal alloys, aluminum alloys [3][4][5][6][7][8] seem to be the most promising due to their unique combination of physicochemical and mechanical properties, such as low density, high strength to specific weight ratio, ductility and low melting temperature, causing relatively low prices of recycling [9,10]. Additionally, documented investigations [11][12][13][14] prove that the most promising aluminum alloys aimed for the elements exposed to high load and wear are, inter alia, the alloys of 2xxx and 7xxx series.…”