The effect of na and Sr modification on surface tension and volumetric shrinkage of A356 alloy and their influence on porosity formation

In this paper, Sr modifier (300 ppm) was added to 2L99 alloy sand castings to investigate its effect on bifilm defects in the castings. Two different sand molds were used in this study, with good and bad running system designs, to introduce different amounts of bifilm defects into the castings. The mechanical properties of the modified 2L99 castings were compared to the properties of unmodified castings and showed that with high bifilm defect contents (H) the Sr addition reduced the Weibull modulus of the UTS by 67 pct and the Position Parameter by 5 pct, and introduced a bimodal distribution into the Weibull plot of the pct Elongation. However, for castings with low bifilm defect content (L), the Weibull moduli of both the UTS and pct Elongation were significantly improved (by 78 and 73 pct, respectively) with the addition of Sr. The Position Parameter of the pct Elongation was improved by 135 pct. The results suggested that a desirable modification effect can only be achieved while the bifilm defect content in a casting was low.

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“…The cumulative distribution function of the two-parameter Weibull distribution used here is given by Eq. [1]:…”

Section: Methodsmentioning

confidence: 99%

“…[1][2][3] Ba and Ca [4,5] are also reported to have a similar but reduced effect on Si. Of the commonly used modifiers, Sr remains longer in the melt than Na but is well known for its association with enhanced gas porosity.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Sr Modifier Additions on Double Oxide Film Defects in 2L99 Alloy Castings

Chen

Griffiths

2017

Metall Mater Trans A

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“…Emadi et al studied the effect of Sr modification on surface tension of A356 alloy, and found the addition of Sr to A356 alloy decreased the surface tension of the liquid by about 19 pct to 0.64 N/m. 28) The viscosity of A356 melt at eutectic temperature (565…”

Section: Discussionmentioning

confidence: 99%

A Mechanism of Porosity Distribution in A356 Aluminum Alloy Castings

Chang

2002

Mater. Trans.

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The problem of porosity and shrinkage defects in metal casting is complex. Over the years there have been debates on the mechanisms responsible for their formation. In this study A356 aluminum alloy with different hydrogen contents in the melts were cast in a permanent mold and the porosity content and thermal parameters were measured. A simple mechanism was proposed to explain the porosity distribution in the casting. In the mechanism both the roles of interdendritic feeding resistance by Darcy's law and kinetic hydrogen diffusion into the pore are involved. By differentiating one factor in the model, and comparing the prediction with the experimental data, the study suggests that both factors should be taken into consideration to satisfactorily explain the porosity distribution in the castings.

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“…Na could also have an indirect influence via melt properties such as surface tension (i.e., reduced) and solidification contraction (increased) but the exact mechanisms are not known. 37 …”

Section: Expansionmentioning

confidence: 99%

Suitability of various complex hydrides for foaming aluminum alloys

et al. 2013

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Some hydrides that could replace TiH 2 as the hitherto most suitable blowing agent for foaming aluminum alloys were investigated. Hydrides taken from the group MBH 4 (M 5 Li, Na, K) and LiAlH 4 were selected since these have not been studied in the past although their decomposition characteristics appear to be suitable. Foamable precursors of alloy AlSi8Mg4 were manufactured by pressing blends of metal and blowing agent powders. Powders, precursors and precursor filings were studied by mass spectrometry to obtain the hydrogen desorption profile. Foaming experiments were conducted with simultaneous x-ray radiographic monitoring. Two Li-containing blowing agents were found to perform well and can be considered alternatives to TiH 2 .

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The effect of na and Sr modification on surface tension and volumetric shrinkage of A356 alloy and their influence on porosity formation

Cited by 124 publications

References 6 publications

The Effect of Sr Modifier Additions on Double Oxide Film Defects in 2L99 Alloy Castings

The Effect of Sr Modifier Additions on Double Oxide Film Defects in 2L99 Alloy Castings

A Mechanism of Porosity Distribution in A356 Aluminum Alloy Castings

Suitability of various complex hydrides for foaming aluminum alloys

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