Influence of hydrogen levels on porosity and mechanical properties of Mg alloy castings

Wu, Siyu; Song, Xu; Fukuda, Y.; Nakaé, Hitoshi

doi:10.1179/136404608x361756

Cited by 6 publications

(4 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can be seen that the network eutectic phases distributed in the α-Mg grain boundaries. According to the EDS results in Table 2 and XRD analyses, the eutectic phase is identified as Mg 24 (Gd, Y) 5 . Figures 2(c) and 2(d) are the TEM images of the eutectic phase.…”

Section: Microstructurementioning

confidence: 99%

“…where N is the molar concentration of hydrogen, and P is the partial pressure of hydrogen. Taking N=1 and P=1.01×10 5 Pa as the standard state, the standard dissolution free energy of hydrogen in Mg melt can be expressed as: where R is the gas constant (R=8.314 J•mol -1 •K -1 ), and K is the equilibrium constant. The solute is dilute and according to the…”

Section: Formation Mechanism Of (Y Gd)hmentioning

confidence: 99%

“…The quality of Mg-Gd-Y-Zr alloy castings is closely related to melting condition, solidification process and humidity in the surrounding environment [3,4] . It is well known that magnesium alloy melt has a strong hydrogen absorption capacity, and it is easy to form shrinkage porosity defects during the casting process [5][6][7] . Therefore, degassing treatment during the melting process is essential.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

(Y, Gd)H2 phase formation in as-cast Mg-6Gd-3Y-0.5Zr alloy

Wang

Wang³

et al. 2021

China Foundry

View full text Add to dashboard Cite

In this work, a new (Y, Gd)H 2 precipitate was identified and systematically investigated in the ascast Mg-6Gd-3Y-0.5Zr alloy by XRD, SEM with EDS, TEM with EDS techniques and thermodynamics analysis. Results show that the as-cast alloy contains α-Mg, Mg 24 (Gd, Y) 5 , and (Y, Gd)H 2 phase. The (Y, Gd)H 2 phase usually forms near the eutectic phase Mg 24 (Gd, Y) 5 or in the α-Mg grains, displaying a rectangle-shape. The Mg 24 (Gd, Y) 5 and (Y, Gd)H 2 phases crystalize in bcc and fcc structure, respectively, and the (Y, Gd)H 2 phase has a semi-coherent relationship with α-Mg matrix. The thermodynamics calculation results reveal that the hydrogen dissolved in the melt leads to the formation of hydrides. It is also found that the (Y, Gd)H 2 hydride can form directly from the liquid phase during solidification. Additionally, it can precipitate by the decomposition of Mg 24 (Gd, Y) 5 phase due to absorbing hydrogen from the remaining melt.

show abstract

Section: Microstructurementioning

confidence: 99%

Section: Formation Mechanism Of (Y Gd)hmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

(Y, Gd)H2 phase formation in as-cast Mg-6Gd-3Y-0.5Zr alloy

Wang

Wang³

et al. 2021

China Foundry

View full text Add to dashboard Cite

show abstract

“…It was widely suggested that pore defects in Al-alloy and Mg-alloy castings contained hydrogen that diffused from the melt. [10,24,25,31] In addition, Campbell [10] conjectured that hydrogen was able to diffuse from an Al-alloy melt into an entrainment defect, resulting in expansion of the defect. Yue and Griffiths observed pore defect expansion when re-melting a liquid A356 alloy sample under Synchrotron X-rays.…”

Section: Pore Gas Analysermentioning

confidence: 99%

Consumption of Entrained Gases Within Bifilms During a Mg-Alloy Casting Process

Davies

Luo

2021

Metall Mater Trans B

View full text Add to dashboard Cite

The formation of entrainment defects, (also known as double oxide film defects or bifilms), caused by the entrapment of a doubled-over surface oxide film containing a small amount of local atmosphere, has been investigated by combining practical experiments using a commercial-purity Mg-alloy under protective gases, with theoretical thermodynamic calculations. Evolution of the entrainment defects was studied, and a double-layered structure of their oxide films was found, which was different from the single-layered structure of the Mg-alloy melt surface films that have been previously reported. A pore gas analyzer was used to analyze the gas trapped within the defects from which H2 and N2 (from the air) were detected. It was found that entrapped gases can be depleted through reactions with the surrounding liquid Mg-alloy, resulting in the oxide films growing together in the melt. Transformation of the entrained gas to solid-phase compounds could reduce the void volume of the defects, thus probably diminishing the negative effect of the entrainment defects on the quality of castings.

show abstract