Formation of Fold Defects in Permanent Mold Cast AE42 Magnesium Alloy

Application of magnesium alloys potentially plays a key role in weight reduction of automotive and aerospace components. Majority of magnesium components are manufactured via the high-pressure die-casting (HPDC) or permanent-mold casting (PMC) processes. In general, castability of magnesium alloys is comparable to aluminum alloys. However, unique defects related to the high susceptibility of magnesium to rapidly solidify, dissolve hydrogen or form oxides potentially contribute to material failure. In this research, AE42 magnesium alloy castings were manufactured via the PMC process. Formation of fold defects in regions of high melt turbulence was observed on the macro-scale as visible surface flow-lines. Microstructural analysis revealed that folds in the AE42 alloy we related to the rapid solidification and short alloy freezing range. Further, segregation of Al2RE intermetallics at the metal front hindered proper fusion of merging metal fronts.

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The Effect of LFC Process Variables on Solidification and Thermal Response of AZ91E Magnesium Alloy Castings

10.32920/ryerson.14652165 ◽

2021 ◽

Author(s):

Lukas Bichler

Keyword(s):

Thermal Analysis ◽

Magnesium Alloy ◽

Magnesium Alloys ◽

Metal Flow ◽

Mold Filling ◽

Second Phase ◽

Process Variables ◽

Pyrolysis Products ◽

Alloy Castings ◽

Non Equilibrium

Magnesium alloys are gaining in popularity as materials of choice for automotive and aerospace applications. Magnesium alloys have the lowest density of all structural metals, effectively making their specific properties highly attractive. Lost Foam Casting (LFC) is a novel near-net-shape manufacturing process utilizing expanded polystyrene (EPS) as a mold filler. Presence of the EPS in the casting cavity promotes formation of unique casting defects.These include misruns, folds, entrapped polystyrene pyrolysis products and potentially increased levels of gas porosity. There is very little published literature on the feasibility of casting magnesium alloys by the LFC process. This research was an attempt to evaluate the effect of selected LFC process variables on AZ91R magnesium alloy castings produced by the LFC process. In this work, the effect of melt superheat, casting section thickness, EPS foam properties and the application of vacuum during mold filling were investigated and correlated to the casting quality and molten flow behavior. Further, detailed thermal analysis was carried out to determine the solidification history of the castings. The results of the thermal analysis were used to determine the effect of the cooling rate on the development of the casting microstructure. Moreover, the morphology and the mode of second phase (Mg17Al12) precipitation were studied and quantified. The results suggest that application of vacuum during the mold filling process increased the metal flow lengths. However, the casting soundness deteriorated due to the applied vacuum. Variations in the density of the vacuum cast horizontal bars were explained through the presence of partially solidified metal. The molten metal flow was further influenced by the foam density and bead fusion. Greater flow lengths were observed in the high density 1.6 pcf foam castings. in the low density 1.3 pcf foam castings, numerous casting defects were associated with the presence of the liquid-EPS pyrolysis products. In general, the thermal analysis suggested that non-equilibrium alloy solidification promoted the formation of the lamellar non-equilibrium Mg17Al12 precipitate, and this was confirmed by optical microscopy.

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Magnesium Alloy Castings, Permanent Mold 9.0A1- 2.0Zn (AZ92A-T6) Solution and Precipitation Heat Treated

10.4271/ams4484 ◽

2000 ◽

Author(s):

Keyword(s):

Magnesium Alloy ◽

Permanent Mold ◽

Heat Treated ◽

Alloy Castings ◽

Precipitation Heat

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Effect of Sn Content on Heat Resistance of Mg-3%Al-1%Si Alloy for Casting

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.1071 ◽

2018 ◽

Vol 941 ◽

pp. 1071-1076

Author(s):

Seiji Saikawa ◽

Manabu Mizutani ◽

Nozomu Kawabe

Keyword(s):

Magnesium Alloys ◽

Optical Microscope ◽

Permanent Mold ◽

Power Train ◽

Suitable Material ◽

Specific Strength ◽

Heat Resistant ◽

High Specific Strength ◽

Mold Casting ◽

Mobile Industry

Magnesium alloys have the characteristic with high specific strength and lightweight property, it is widely used for auto mobile industry. Heat-resistant magnesium alloy is focused as a suitable material for weight reduction of the engine and power train parts in automotive field. In this study, microstructure and heat-resistant property in Mg-3mass%Al-1mass%Si (Mg-3%Al-1%Si) alloy with containing large amount of Sn (tin) were investigated. The alloys produced by permanent mold casting were investigated by optical microscope (OM), scanning electron microscopy (SEM) and measuring of bolt load retention at 423K. The heat-resistant property of Mg-3mass % Al-1mass % Si alloy with containing 6-13masss%Sn was higher compared with Sn free alloy and conventional Magnesium alloys (e.g. AZ91 and AM60 alloys).

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Magnesium Permanent Mold Castings Optimization

Materials Science Forum ◽

10.4028/www.scientific.net/msf.690.65 ◽

2011 ◽

Vol 690 ◽

pp. 65-68 ◽

Cited By ~ 51

Author(s):

Fady Refaat Elsayed ◽

Norbert Hort ◽

Mario Alberto Salgado Ordorica ◽

Karl Ulrich Kainer

Keyword(s):

Magnesium Alloys ◽

Casting Process ◽

Mold Temperature ◽

Holding Time ◽

Permanent Mold ◽

Melt Temperature ◽

Cast Part ◽

Mold Casting ◽

Permanent Mold Castings ◽

Inhomogeneous Properties

Permanent mold casting is a well-established route for casting large magnesium alloys components. Casting parameters like superheat, mold temperature, and holding time can often result in inhomogeneous properties, porosity, and segregation problems in the cast part. In order to optimize the casting process, control of the casting parameters including mold temperatures and holding times is essential to promote directional solidification, and ensure defect free homogenous structure. Binary Mg-9wt.%Al and Mg-10wt.%Gd alloys were used to investigate the effect of casting parameters such as melt temperature and holding time on the part macro and microstructure.

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