Pore Formation In Cast Metals And Alloys

EXPERIMENTAL INVESTIGATION AND NUMERICAL …

to microporosity formation, and to quantify the pore nucleation kinetics at given casting conditions. Furthermore, this model was applied to study the effect of oxide inclusions on pore nucleation kinetics. Castings were prepared under different casting conditions aimed at manipulating the tendency to form and entrain oxides in the melt.

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Casting defect - Wikipedia

A casting defect is an undesired irregularity in a metal casting process. Some defects can be tolerated while others can be repaired, otherwise they must be eliminated. They are broken down into five main categories: gas porosity, shrinkage defects, mould material defects, pouring metal defects, and metallurgical defects.

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(PDF) Physics of microporosity formation in casting alloys ...

In the case of aluminum alloys, pore formation is mainly attributed to inadequate feeding of solidification shrinkage and the rejection of dissolved hydrogen during the solidification of the alloy ...

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Assessment of Mechanism of Pore Formation in Directionally ...

The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means of bifilm content, size and distribution in A356 alloy.

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Oxide Film and Porosity Defects in Magnesium Alloy AZ91

20 years. More recently, new mechanisms of pore formation based on entrainment of oxide films during the filling of aluminum alloy castings have been identified and documented [2-7]. Oxide film defects are formed when the oxidized surface of the liquid metal is folded over …

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Investigation on Double Oxide Film Initiated Pore ...

Abstract. The most common, and in fact, the most deleterious defects of aluminum casting alloys are the so-called double oxide films or bifilms, which have a central role in porosity formation, as they can easily unfurl and inflate into pores during the solidification of the alloys.

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Reducing the Porosity in Die-Cast Magnesium Alloys during ...

The characteristic of gas source in die-cast magnesium alloys and the process of pore formation during laser welding are studied by some experiments including analysis of characteristic parameters ...

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Mechanisms of porosity formation in aluminum. - Free ...

Sep 01, 1992· Q.T. Fang, P.N. Anyalebechi, "Effects of Solidification Conditions on Hydrogen Porosity Formation in Aluminum Alloy Castings," TMS Annual Meeting of Light Metals, p 477 (1988). 3. K.J. Brondyke and P.D. Hess, "Interpretation of Vacuum Gas Test Results for Aluminum Alloys," Transactions of AIME, vol 230, p 1542 (1964).

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Investigation on Double Oxide Film Initiated Pore ...

The most common, and in fact, the most deleterious defects of aluminum casting alloys are the so-called double oxide films or bifilms, which have a central role in porosity formation, as they can ...

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Materials | Free Full-Text | Intrinsic and Extrinsic ...

The metallurgy of cast aluminum alloys has always been considered to be different from that of wrought alloys. Metallurgists have been taught that pores are intrinsic in cast aluminum alloys and that mechanical properties in cast aluminum alloys are controlled by dendrite arm spacing, the presence of Fe-bearing particles, and the size of Si particles in Al–Si alloys, which fracture and ...

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Kinetic analysis of pore formation in die-cast metals and ...

The mechanism of gas pore formation during the vacuum die casting was analyzed. • With the reduction of absolute pressure, the number and size of porosity defects were significantly reduced. • Kinetic analysis was used to confirm the influence of vacuum on the formation of vortices and pores.

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Welding of Magnesium Alloys | IntechOpen

Nov 17, 2011· a) Pores in die-cast AM60B alloy welded using a 1.5 kW CW Nd:YAG laser (Zhao and Debroy, 2001), and (b) Formation of large pores in the FZ due to the expansion and coalescence of the preexisting pores in base die-cast AM60B alloy (Cao et al., 2006).

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Modeling of porosity formation and feeding flow during ...

Porosity is one of the most important defects in metal casting. To quantitatively predict the porosity formation during casting two numerical models are developed for steel and aluminum alloys respectively. For steel, a multi-phase model is developed that predicts melt pressure, feeding flow, porosity (both microscopic and macroscopic), and riser pipe formation during casting.

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Direct observation of the effect of strontium on porosity ...

(2000). Direct observation of the effect of strontium on porosity formation during the solidification of aluminium-silicon alloys. International Journal of Cast Metals Research: Vol. 13, No. 4, pp. 185-198.

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Impurity Effects on Pore Formation at Al2O3/Alloy Interfaces

metal surface by plastic flow to avoid pore formation and scale separation [11]. Experimental A Fe-40at%Al alloy containing 27.6 wppm of sulfur impurity, from Oak Ridge National Laboratory, was used for the study. The alloy was received as a ~ 1 mm thick hot-rolled sheet from an arc melted casting. It was annealed in He at 1100°C for

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Porosity in Metals | Defects | Solidification | Metallurgy

The gas-bubble formation is also dependent on the local pressure in the liquid. If a liquid metal solidifies under sufficiently high pressure, such as in pressure die-casting process (liquid metal is forced under high pressure into steel-dies), the gas is made to remain dissolved in the metal (Sieverts Law), gas evolution is prevented.

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Aluminium-Silicon Casting Alloys

The copper is used for precipitation hardening (Al 2 Cu, Al 5 Mg 8 Cu 2 6), should that be necessary.Iron is to be avoided if possible, since it can form plate-like precipitates (Al 5 FeSi) which embrittle the casting and can block the flow of liquid metal in the mould. The strontium, when added delibrately, helps to modify the shape of the silicon, rather as does sodium.

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Pore formation in cast metals and alloys | SpringerLink

The observations are in support of a non-nucleation mechanism of pore formation playing a major role in the occurrence of such defects in cast metals. Further, in gas-containing alloy melts the critical amounts of gas required for single and multiple pore nucleation …

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Casting properties [SubsTech]

May 31, 2012· Dr. Dmitri Kopeliovich Foundry is a process of producing metal castings.. Casting is an operation of shaping metal by pouring it in the liquid state into a mold followed by solidification. Casting is also a metal detail, produced as a result of pouring a metal into a mold. In some cases casting is the only method of shaping a metal or alloy: when the alloy is not malleable and therefore it’s ...

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Gas Pore Formation in Lost Foam Casting of AZ91H Mg Alloy ...

The lower porosity was caused by the extra hydrogen solubility. The pore formation mechanism of the AZ91H alloy in LFC was similar to that of the A356 alloy but the critical temperature for generating a different mechanism of pore formation is higher in the A356 alloy by as much as about 323 K.

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Process to manufacture pore-free cast-on-strap joints for ...

From further experiments where different parameters like chemical composition and thickness of plate lugs, temperature of lead-based strap alloys, and different cast-on-strap joint types were tested, it was found that the main mode to avoid the formation of pores in the cast-on-strap joints was to eliminate the residues of lead oxides, grease ...

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Solidification of Metals and Alloys | Metals Handbook Desk ...

Solidification is a comprehensive process of transformation of the melt of metals and alloys into a solid piece, involving formation of dendrites, segregation which involves change in composition, zone formation in final structure of the casting, and microporosity formation during shrinkage.

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Modeling the influence of multi-component alloying ...

Modeling the influence of multi-component alloying additions on microstructure and pore formation in cast aluminum alloys By Peter D. Lee, Junsheng Wang and Robert C. Atwood

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Manufacturing Chapter 10 Flashcards | Quizlet

Consider an alloy poured into a mold, where the exterior solidified and a solidification front progresses towards the casting center. In an alloy with a large freezing range, the presence of a large mushy zone is more likely to occur and, thus, the formation of microporosity. However, in an alloy with a short freezing range, the formation of gross

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Modeling of Porosity Formation in Aluminum Alloys

Keywords: porosity, aluminum alloys, hydrogen diffusion Abstract A new approach based on microsegregation of gas dissolved in the melt is used to model pore formation during the solidification of aluminum alloys. The model predicts the amount and size of the porosity in a solidified casting. Computation of the micro-/macro-scale gas species

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Chapter 10 Fundamentals of Metal Casting

Fundamentals of Metal Casting 10.1 Introduction One of the oldest processes used to shape metals is the casting process (CP) which basically involves: 1. Pouring molten metal into a mold cavity (patterned after the part to be mfg), 2. Allowing it to solidify (cool), and 3. Removing the part from the mold.

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Analysis of Pore Formation at Oxide–Alloy Interfaces—II ...

Jan 08, 2005· Abstract. Oxidation of Metals, Vol. 59, Nos. 1/2, February 2003 ( 2002) Analysis of Pore Formation at Oxide–Alloy Interfaces—II: Theoretical Treatment of Vacancy Condensation for Immobile Interfaces F. Gesmundo† and P. Y. Hou* Receiûed December 4, 2001; reûised May 21, 2002 Void generation at scale–alloy interfaces during the oxidation of binary alloys as a result of matter …

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Microporosity Formation during the - The Minerals, Metals ...

The same two alloys, Al-4Cu and Al-12Cu, were also cast into an instrumented permanent mold wedge casting rig using the methodology described in Reference 3 and the conditions listed in Table I. From a location at the middle of the wedge in thickness, and 100 mm from the bottom, a 2 mm diameter cylinder was machined and analyzed using the same ...

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Pore structure and mechanical properties of directionally ...

Pore structure and mechanical properties of directionally solidified porous aluminum alloys * Hao Hai Male, born in 1969, Ph.D., Professor. His research interests mainly focus on solidification control, casting technology of light metals, porous materials. He has published more than ninety technical papers. E-mail: [email protected]

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Modeling microporosity in aluminum–silicon alloys: a ...

Feb 01, 2001· The modeling of pore formation during the solidification of aluminum alloys has changed tremendously over the past four decades, ranging from analytic solutions to highly complex simulations of evolving porosity and microstructure with stochastic nucleation and growth.

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