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

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.

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

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.

Effects of Strain Rate and Heat Treatment on the Tensile Property of 1Mn1Zn4Y Magnesium Alloy

2011 ◽  
Vol 311-313 ◽  
pp. 583-586
Author(s):  
Xiu Zhi Zhang ◽  
Ying Jie Li ◽  
Yi Shuai Zhang
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Grain Size ◽  
Magnesium Alloy ◽  
Strain Rate ◽  
Magnesium Alloys ◽  
Tensile Property ◽  
Tensile Tests ◽  
Second Phase ◽  
Dispersed Particles

In this paper, the effect of heat treatment and strain rate on the tensile property of extruding magnesium alloys 1Mn1Zn4Y is studied by using tensile tests. It can be concluded that because the grain size of the sample with solid solution (T4) is coarser than that of the sample without heat treatment，the elongation and the strength of the specimen treated with solid solution are lower. However, owing to many fine and dispersed particles of the second phase precipitated from the solid solution, the strength of sample treated with solid solution + aging (T6) is the highest.

Formation of Fold Defects in Permanent Mold Cast AE42 Magnesium Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1591-1595
Author(s):  
Lukas Bichler ◽  
Comondore Ravindran
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Microstructural Analysis ◽  
Surface Flow ◽  
Rapidly Solidify ◽  
Permanent Mold ◽  
Process Formation ◽  
Mold Casting ◽  
Macro Scale ◽  
Alloy Castings

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.

Structural Stability of Welded Joints of Magnesium Alloy EZ33A-T5

2014 ◽  
Vol 782 ◽  
pp. 408-414
Author(s):  
Robert Kocurek ◽  
Janusz Adamiec
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Welded Joints ◽  
Welded Joint ◽  
Research Work ◽  
Structure And Properties ◽  
Alloy Casting ◽  
Shrinkage Cracks ◽  
Lack Of Information ◽  
Alloy Castings

Magnesium alloys of Mg-Zn-RE-Zr group are characterized by creep resistance up to 250°C, good castability, absence of the microporosity and gas corrosion resistance. Defect of these alloys are low mechanical properties at ambient temperature. Magnesium alloys are used in the automotive, aerospace and defense industries, mainly as gravitational casts to sand moulds or die-casting. Casting defects often appear in these casts (misruns, micro-shrinkage, cracks), especially for large-size castings. The welding technologies are most often applicable to repair of casts, mainly non-consumable electrode welding in the inert-gas cover. Welded joints made of magnesium alloys should have properties at least the same as the ready cast, in particular it should ensure stability of the structure and properties of all welded joint in working temperature. In the literature there is a lack of information about stability and properties of welded joints of Mg-4E-3Zn (EZ33A-T5 acc. to ASTM B80) alloy castings. In research work determined the structure of welded joints of Mg-4RE-3Zn alloy casting after stress-relief annealing and defined changes of structure and properties during long-term annealing at the temperature of 250°C. It was found that the structure of welded joint of casting alloy Mg-4RE-3Zn is stable at the temperature of 250°C through at least 1000 hours. The hardness of tested joints equal 80 HV. Therefore welding technologies can be used for repair of magnesium alloy casts with addition of zinc and rare earth elements.

The Repair Welding Technology of Casts Magnesium Alloy QE22

2013 ◽  
Vol 212 ◽  
pp. 81-86 ◽  
Author(s):  
Robert Kocurek ◽  
Janusz Adamiec
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Research Work ◽  
Inert Gas ◽  
Repair Welding ◽  
Welding Technology ◽  
Alloy Castings ◽  
Stable Connection

Alloys from group Mg-Ag-RE-Zr are characterized by creep resistance up to 200°C, good casting and mechanical properties. Defects of magnesium alloys are propensity to cracks and deformations during heat treatment, low corrosion resistance. Welding technologies are most often use to repair of casts, mainly nonconsumable electrode welding in inert gas cover. About possibility repair or regeneration of magnesium alloy castings by welding depends on their weldability. Weldability of most magnesium alloys is good however, welding and surfacing cast elements create many problems. The purpose of this research work was develop a repair welding technology of casts magnesium alloy. Research project consisted of weldings and padding trials, microstructure and mechanical properties tests. Presented research results in this paper support conclusion that casts alloy QE22 reveal susceptibility to stable connection.

Effect of Cryogenic Treatment on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

2011 ◽  
Vol 686 ◽  
pp. 53-56 ◽  
Author(s):  
Jie Li ◽  
Xian Quan Jiang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Cryogenic Treatment ◽  
Optimal Combination ◽  
Az31 Magnesium Alloy ◽  
Second Phase ◽  
Microstructure And Mechanical Properties ◽  
Az31 Magnesium Alloys

The microstructure and mechanical properties of AZ31 magnesium alloys were investigated in this paper. AZ31 magnesium alloys were cryogenically treated at -196°C for 1, 5 and 24 hours, respectively. The results showed the grains of AZ31 were initially refined and grew up with the increase of cryogenic time, the second phase decreased gradually, and the rigidity and tensile strength decreased drastically and then increased. As a result, AZ31 magnesium alloys with 1 hour cryogenic treatment were able to obtain the optimal combination properties.

Warm Forging Characteristics of AZ31 Alloy

2007 ◽  
Vol 26-28 ◽  
pp. 437-440 ◽  
Author(s):  
Yong Nam Kwon ◽  
Young Seon Lee ◽  
Jung Hwan Lee
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Industrial Application ◽  
Az31 Alloy ◽  
Significant Activity ◽  
Process Variables ◽  
Flow Uniformity ◽  
Processing Variables ◽  
Experimental Works ◽  
Warm Forging

Industrial application of magnesium alloys has increased significantly recently. However, wrought magnesium alloys still have a lot of technical challenges to be solved for more applications. First of all, low formability of wrought alloys should be improved by optimizing the processing variables. In the present study, the effect of process variables such as forging temperature and forging speed were investigated to forgeability of magnesium alloy. To understand the effect of process variables more specifically, both numerical and experimental works have been carried out on the model which contains upsetting geometry. Forgeability of AZ31 alloy was found to depend more on the forging speed rather than temperature. Forged sample showed a significant activity of twinning, which was found to be closely related with flow uniformity.

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