Solidification Curves for Commercial Mg Alloys Determined from Differential Scanning Calorimetry with Improved Heat-Transfer Modeling

Mirković, Djordje; Schmid–Fetzer, Rainer

doi:10.1007/s11661-007-9237-z

Cited by 28 publications

(11 citation statements)

References 45 publications

(92 reference statements)

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“…Thus, it may be deduced that in contrast to the AZ61 and AZ91 alloys, due to small volume fraction of γ precipitates in AZ31 Mg alloy, no significant signal related to precipitation of γ phase or γ eutectic melting would be detected. A similar behavior was observed in thermal analysis curve of AM50 magnesium alloy 16 . However, solidification process of Mg-Al-Zn system is far from an equilibrium condition even at extremely slow cooling rate of 1 K/min 11 , and coring in α-Mg solid solution occurs and γ phase forms in the microstructure of Mg-Al alloys with down to about 2 wt.…”

Section: Resultssupporting

confidence: 85%

An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy

2014

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In non-equilibrium conditions, the coring phenomena may occur in the α-Mg solid solution and γ-Mg 17 Al 12 phase forms in the microstructure of AZ magnesium alloy series. This eutectic phase may introduce detrimental effect on workability of wrought alloys. In the present work, the dissolution characteristics of γ phase have been investigated in AZ31 wrought magnesium alloy. Considering the eutectic temperature of AZ31 alloy, the homogenization treatment was executed in temperature range of 300-437 °C (i.e., somewhat below eutectic melting temperature of γ precipitate) and 437-500 °C (i.e., higher eutectic melting temperature of γ precipitate) for different durations. A thorough microstructural investigation and also thermodynamic calculations were executed. The results indicated that the dissolution rate of γ phase is very low even at temperatures just below the eutectic point of the alloy, whereas it dramatically increases at temperatures higher than eutectic point. Moreover, it is suggested that partial melting of γ phase due to eutectic melting reaction (α+γ→L) may lead to reduced formability.

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Section: Resultssupporting

confidence: 85%

An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy

2014

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“…One can found that f s(T) increases rapidly from about 0.2 at T ¼ 590 C (863 K) to about 0.5 to 0.6 when vibration starts at lower temperatures of T ¼ 570 C (843 K) and T ¼ 560 C (833 K). The calculated fraction solids are consistent with delicate measurements conducted in a differential scanning calorimeter with a mathematical heattransfer model 23) and thermodynamic prediction by the CALPHAD approach 24) for the AZ91D alloy. Moreover, good agreement can be found between this theoretical calculation and semisolid casting experiment, in which coarsening is assumed to be negligible from the semisolid state to the compete crystallization.…”

Section: Discussionsupporting

confidence: 77%

Effect of Vibration Timing on the Microstructure and Microtexture Formation of AZ91D Magnesium Alloys during Electromagnetic Vibration

Tamura

Omura

et al. 2009

Mater. Trans.

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For an electric conductor in a static magnet, electromagnetic vibration (EMV) is activated to take place when an alternating current flows through the conductor in the direction perpendicular to that of the magnetic field. Following the principle, in the present study we solidified the AZ91D magnesium alloys at various vibration timing moments and then examined the microtexture and microtexture. It is revealed that the decrease of the starting vibration temperature in the mushy zone results in coarse microstructures with large dendritic fragments and eventually with fully developed dendrites that are well oriented with their basal planes being perpendicular to the direction of magnetic field. It has been demonstrated that melt flow is responsible for structural refinement during EMV processing due to the electrical resistivity difference of the solid and liquid. In mushy zone, when vibration is imposed at a low temperature, the fraction solid of the primary phase prior to vibration has been large, which makes the semisolid slurry rather viscous. The intensity and scale of the melt flow is weakened and thus yielding coarse structures. Meanwhile, as the magnetic field is imposed throughout the entire experimental operation, the magnetization torque takes into effect to orient dendrites. The bridging of dendrites may have been accomplished at low vibration temperature before EMV is activated. In this case, the magnetization torque becomes predominant to align crystals along their preferential crystallographic orientation and thus resulting in highly oriented textures.

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“…[23,24] Nonferrous tube materials were also considered for application in this study, but were rejected for the reasons given in Section VII-A-1.…”

Section: B Alternative Nonferrous Tube Materialsmentioning

confidence: 99%

“…This temperature is only 42 K higher than the practical liquidus temperature of the alloy, defined by the start of the massive crystallization of the (Mg) phase. [24] After slow cooling in air, the cross section in Figure 3 shows an approximately 30-lm-thick contiguous intermetallic compound layer with a fairly constant aluminum composition of approximately 26 wt pct aluminum and 74 wt pct Fe, or Fe 58 Al 42 (at. pct).…”

Section: A Reaction Between Unprotected Steel Tube and Liquid Alloymentioning

confidence: 99%

Directional Solidification of Mg-Al Alloys and Microsegregation Study of Mg Alloys AZ31 and AM50: Part I. Methodology

Mirković

Schmid–Fetzer

2009

Metall Mater Trans A

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An appropriate method for the directional solidification (DS) of magnesium alloys AZ31 and AM50 was developed to enable the investigation of microstructures and microsegregation under controlled solidification conditions. These liquid alloys, containing both magnesium and aluminum, are highly reactive and attack both standard ceramic and metallic container materials. An integrated approach is developed that is comprised of the dedicated boron nitride (BN) protection of selected steel tube material and limitation of the melt temperature, with the retention of sufficiently high thermal gradients for DS. The well-known Scheil method for the thermodynamic calculation of segregation is extended to reflect the solute profiles of components in all precipitating phases. This ''Scheil-total'' profile is more realistic; its integral reflects the bulk composition of a multiphase alloy. It also predicts the primary crystallizing Al-Mn intermetallic phase experimentally detected in the microstructure. This prediction is also confirmed by the application of an advanced processing of quantitative electron probe microanalysis (EPMA) mapping data.

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Solidification Curves for Commercial Mg Alloys Determined from Differential Scanning Calorimetry with Improved Heat-Transfer Modeling

Cited by 28 publications

References 45 publications

An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy

An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy

Effect of Vibration Timing on the Microstructure and Microtexture Formation of AZ91D Magnesium Alloys during Electromagnetic Vibration

Directional Solidification of Mg-Al Alloys and Microsegregation Study of Mg Alloys AZ31 and AM50: Part I. Methodology

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