scholarly journals Influence of Bifilm Defects Generated during Mould Filling on the Tensile Properties of Al–Si–Mg Cast Alloys

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 160
Author(s):  
Mahmoud Ahmed El-Sayed ◽  
Khamis Essa ◽  
Hany Hassanin
Keyword(s):  
Tensile Strength ◽  
Oxide Film ◽  
Hydrogen Content ◽  
Mould Filling ◽  
Cast Alloys ◽  
Alloy Castings ◽  
Factorial Design Of Experiments ◽  
Position Parameter ◽  
Hydrogen Level ◽  
Full Factorial

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this work, the effect of two important casting parameters (the filtration and hydrogen content) on the properties of Al–7 Si–0.3 Mg alloy castings was studied using a full factorial design of experiments approach. Casting properties such as the Weibull modulus and position parameter of the elongation and the tensile strength were considered as response parameters. The results suggested that adopting 10 PPI filters in the gating system resulted in a considerable boost of the Weibull moduli of the tensile strength and elongation due to the enhanced mould filling conditions that minimised the possibility of oxide film entrainment. In addition, the results showed that reducing the hydrogen content in the castings samples from 0.257 to 0.132 cm3/100 g Al was associated with a noticeable decrease in the size of bifilm defects with a corresponding improvement in the mechanical properties. Such significant effect of the process parameters studied on the casting properties suggests that the more careful and quiescent mould filling practice and the lower the hydrogen level of the casting, the higher the quality and reliability of the castings produced.

scholarly journals Effect of Casting Conditions on the Fracture Strength of Al-5 Mg Alloy Castings

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Fawzia Hamed Basuny ◽  
Mootaz Ghazy ◽  
Abdel-Razik Y. Kandeil ◽  
Mahmoud Ahmed El-Sayed
Keyword(s):  
Mechanical Properties ◽  
Oxide Film ◽  
Oxide Films ◽  
Bulk Liquid ◽  
Sand Cast ◽  
Mould Filling ◽  
Surface Turbulence ◽  
Film Content ◽  
Cast Alloys ◽  
Alloy Castings

During the transient phase of filling a casting running system, surface turbulence can cause the entrainment of oxide films into the bulk liquid. Previous research has suggested that the entrained oxide film would have a deleterious effect on the reproducibility of the mechanical properties of Al cast alloys. In this work, the Weibull moduli for the ultimate tensile strength (UTS) and % elongation of sand cast bars produced under different casting conditions were compared as indicators of casting reliability which was expected to be a function of the oxide film content. The results showed that the use of a thin runner along with the use of filters can significantly eliminate the surface turbulence of the melt during mould filling which would lead to the avoidance of the generation and entrainment of surface oxide films and in turn produce castings with more reliable and reproducible mechanical properties compared to the castings produced using conventional running systems.

An Investigation into Double Oxide Film Defects in Aluminium Alloys

2014 ◽  
Vol 783-786 ◽  
pp. 142-147 ◽  
Author(s):  
William D. Griffiths ◽  
A.J. Caden ◽  
M.A. El-Sayed
Keyword(s):  
Oxide Film ◽  
Sem Analysis ◽  
Rate Of Change ◽  
Al Alloy ◽  
Double Oxide ◽  
Air Bubble ◽  
Mould Filling ◽  
Analog Experiment ◽  
Alloy Castings ◽  
Mg Content

When the oxidised surface of a liquid metal is folded over onto itself and entrained double oxide film defects are formed, which form crevices or cracks in the solidified casting, of varying sizes and orientations. These defects not only reduce mechanical properties, but also increase the scatter of properties. This paper reports an analog experiment to study the behavior of the interior atmosphere of double oxide film defects in Al alloy melts of varying Mg content. Air bubbles were trapped in melts of liquid Al alloy which were then solidified after holding for varying periods of time. The composition of the bubbles was subsequently measured using mass spectroscopy. This showed the reaction of oxygen from the bubble atmosphere to form oxides, followed by the consumption of nitrogen to form AlN. Simultaneously, hydrogen from the melt diffused into the air bubble. The changes in composition were used to estimate the rate of change in composition of the interior atmosphere of a typical double oxide film defect of an estimated size. This suggested that double oxide film defects may quickly achieve an interior atmosphere that would consist of a mixture of mainly nitrogen and hydrogen, and that this atmosphere could exist for periods of time greater than the typical solidification times of light alloy castings. In other words, oxide film defects created during mould filling should persist into the solidified casting. In addition, SEM analysis of oxide film defects also suggested the presence of oxide whiskers, which seem to have formed during holding in the melt.

Study on Susceptibility of Hydrogen Embrittlement in a Tool Steel

2007 ◽  
Vol 561-565 ◽  
pp. 103-106 ◽  
Author(s):  
X.T. Wang ◽  
Tadeusz Siwecki
Keyword(s):  
Heat Treatment ◽  
Mechanical Property ◽  
Tensile Strength ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Tool Steel ◽  
Hydrogen Content ◽  
Tensile Tests ◽  
Hydrogen Level ◽  
Low Strain Rate

Susceptibility of hydrogen embrittlement of a super grade AISI 420 tool steel was studied. Tensile samples were cathodically charged to different hydrogen level. Hydrogen induced mechanical property degradation was measured by tensile tests at a low strain rate. Fractography of broken surfaces was observed using SEM. Relationship between hydrogen content and tensile strength and elongation were studied. Critical hydrogen contents were obtained for different heat treatment states. It was found that for annealed materials could stand for a 3.5ppm hydrogen for keeping 80% of original ductility, and the effect of hydrogen on strength was unobvious. However, for material quenched and tempered at 250°C, only 0.3ppm hydrogen could lead the ductility drop to 80% of original. The material quenched and tempered at 500°C was more sensitive on hydrogen, less than 1ppm hydrogen could lead the strength drop to 80% of original.

Modelling of the Effects of Entrainment Defects on Mechanical Properties in a Cast Al-Si-Mg Alloy

2013 ◽  
Vol 765 ◽  
pp. 225-229 ◽  
Author(s):  
Yang Yue ◽  
William D. Griffiths ◽  
Nick R. Green
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Mechanical Strength ◽  
Aluminium Alloy ◽  
Defect Concentration ◽  
Mg Alloy ◽  
Filling Process ◽  
Double Oxide ◽  
Mould Filling ◽  
Alloy Castings

Entrainment defects such as double oxide films and entrapped bubbles occur frequently in aluminium alloy castings during the mould-filling process, and are very detrimental to both mechanical properties, and reproducibility of casting properties. In this study a modelling algorithm was used to predict the formation and distribution of entrainment defects in Al-Si-Mg alloy castings. The tensile strength of cast test bars was compared with either the number of defects, or the defect concentration within the bars obtained from the simulation. A general relationship between the mechanical strength of the cast test bars and the quantity of estimated defects was apparent.

scholarly journals Modelling the temperature change of bifilm defects in Al cast alloys

2019 ◽  
pp. 13-17
Author(s):  
Mahmoud Ahmed El-Sayed
Keyword(s):  
Oxide Film ◽  
Fatigue Properties ◽  
Al Alloy ◽  
Heat Distribution ◽  
Cfd Model ◽  
Double Oxide ◽  
Cast Alloys ◽  
Alloy Castings ◽  
Film Defect ◽  
Surrounding Liquid

Double oxide films (bifilms) are significant defects in the casting of light alloys, and have been shown to decrease tensile and fatigue properties, and also increase their scatter, making casting properties unreproducible and unreliable. Recent research has suggested that the nature of oxide film defects may change with time, as the air inside the bifilm would react with the surrounding melt leading to its consumption, which may enhance the mechanical properties of Al alloy castings. It was suggested that in a pure Al melt, oxygen within the bifilm atmosphere would be consumed first to form alumina, then nitrogen would react to from AlN. A CFD model of the heat distribution associated with the reactions between the interior atmosphere of a double oxide film defect and the surrounding liquid alloy suggested that highly localized increases in temperature, up to 5000, could occur, over a scale of a few hundred micrometers. Such localized increases in temperature might lead to change the nature of the bifilm causing it to be less harmful to the properties of Al cast alloys.

scholarly journals Modification of Double Oxide Film Defects with the Addition of Mo to An Al-Si-Mg Alloy

2021 ◽  
Author(s):  
Qi Chen ◽  
W. D. Griffiths
Keyword(s):  
Liquid Metal ◽  
Oxide Film ◽  
Cross Sections ◽  
Focused Ion Beam ◽  
Spinel Phase ◽  
Ion Beam ◽  
Transmission Electron Microscopy Analysis ◽  
Double Oxide ◽  
Alloy Castings ◽  
Film Defect

AbstractIn this work, Mo was added into Al melt to reduce the detrimental effect of double-oxide film defect. An air bubble was trapped in a liquid metal (2L99), served as an analogy for double-oxide film defect in aluminum alloy castings. It was found that the addition of Mo significantly accelerated the consumption of the entrapped bubble by 60 pct after holding for 1 hour. 2 sets of testbar molds were then cast, with 2L99 and 2L99+Mo alloy, with a badly designed running system, intended to deliberately introduce double oxide film defects into the liquid metal. Tensile testing showed that, with the addition of Mo, the Weibull modulus of the Ultimate Tensile Strength and pct Elongation was increased by a factor of 2.5 (from 9 to 23) and 2 (from 2.5 to 4.5), respectively. The fracture surface of 2L99+Mo alloy testbars revealed areas of nitrides contained within bi-film defects. Cross-sections through those defects by Focused Ion Beam milling suggested that the surface layer were permeable, which could be as thick as 30 μm, compared to around 500 nm for the typical oxide film thickness. Transmission Electron Microscopy analysis suggested that the nitride-containing layer consisted of nitride particles as well as spinel phase of various form. The hypothesis was raised that the permeability of the nitride layers promote the reaction between the entrapped atmosphere in the defect and the surrounding liquid metal, reducing the defect size and decreasing their impact on mechanical properties.

Parameter Characterization for Elastic Energy Absorption of an Embedded Corrugated Wave Padding Concept

2016 ◽  
Author(s):  
Sean S. Tolman ◽  
Amanda Beatty ◽  
Anton E. Bowden ◽  
Larry L. Howell
Keyword(s):  
Energy Absorption ◽  
Cross Section ◽  
Peak Pressure ◽  
Force Distribution ◽  
Finite Element Analyses ◽  
Performance Metric ◽  
Physical Testing ◽  
Physical Tests ◽  
Factorial Design Of Experiments ◽  
Full Factorial

The parameters of an innovative padding concept were investigated using Finite Element Analyses (FEA) and physical testing. The concept relies on a compliant corrugation embedded in an elastic foam to provide stiffness for force distribution and elastic deformation for energy absorption. The shape of the corrugation cross section was explored as well as the wavelength and amplitude by employing a full factorial design of experiments. FEA results were used to choose designs for prototyping and physical testing. The results of the physical tests were consistent with the FEA predictions although the FEA tended to underestimate the peak pressure compared to the physical tests. A performance metric is proposed to compare different padding configurations. The concept shows promise for sports padding applications. It may allow for designs which are smaller, more lightweight, and move better with an athlete than current technologies yet still provide the necessary protective functions.

Effect of Oscillation Speed and Thrust Force on Cortical Bone Temperature During Sagittal Sawing

2013 ◽  
Author(s):  
Steven Micucci ◽  
Gerard Chang ◽  
Eric Smith ◽  
Charles Cassidy ◽  
Amrit Sagar ◽  
...  
Keyword(s):  
Haptic Feedback ◽  
Thrust Force ◽  
Cellular Damage ◽  
Bovine Bone ◽  
Joint Replacement Surgery ◽  
Replacement Surgery ◽  
Factorial Design Of Experiments ◽  
Saw Blade ◽  
Full Factorial ◽  
Cut Surface

Thermal necrosis of bone occurs at sustained temperatures above approximately 47°C. During joint replacement surgery, resection of bone by sawing can heat the bone above this necrotic threshold, thereby inducing cellular damage and negatively affecting surgical outcomes. The aim of this research was to investigate the effect of saw blade speed and applied thrust force on the heating of bone. A sagittal sawing fixture was used to make cuts in cortical bovine bone, while thermocouples were used to characterize the temperature profile from the cut surface. A full factorial Design of Experiments was performed to determine the relative effects of blade speed and applied thrust force on temperature. When comparing the effect of speed to force in the regression analysis, the effect of force on temperature (p < 0.001) was 2.5 times more significant than speed (p = 0.005). The interaction of speed and force was not statistically significant (p > 0.05). The results of this research can be used in the development of training simulators, where virtual surgeries with haptic feedback can be accompanied by the related temperatures in proximity to the cut. From a clinical perspective, the results indicate that aggressive cutting at higher blade speed and greater thrust force results in lower temperatures in the surrounding bone.

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