Dissolution of Eutectic β-Mg17Al12 Phase in Magnesium AZ91 Cast Alloy at Temperatures Close to Eutectic Temperature

Zhu, Tianping; Chen, Zhan W.; Gao, Wei

doi:10.1007/s11665-009-9539-y

Cited by 31 publications

(11 citation statements)

References 24 publications

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“…The lamellae structure (position 3) involves the lamellar growth of Mg 17 Al 12 into the α-Mg grains, corresponding to the discontinuous precipitation [12] . Zhu et al [16] also found the similar β-lamellae structure that mostly appeared to grow near the eutectic Mg 17 Al 12 . This is because these regions have relatively higher Al contents.…”

Section: As-cast Microstructurementioning

confidence: 71%

Effect of solution treatment on microstructure and hardness of rheo-forming AZ91-Y alloy

2016

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M g-Al series alloys have been recognized as ideal materials for lightweight applications in the automotive industry with great development potential because of their low density, high specific strength and stiffness, and excellent cast-ability [1][2] . But their applications are still limited due to the intermetallic phase Mg 17 Al 12 of easy brittleness and unstable structure at elevated temperatures [3][4] . Some efforts have focused on adding some elements like Ca, Si, rare earth (RE) into the alloy matrix for generating new phases to limit the growth of β-Mg 17 Al 12 and modify its microstructure, and eventually improve the mechanical properties of Mg-Al series alloys [4][5][6][7] . Simultaneously, T6 treatment that can also achieve similar goals has attracted more attention due to its low cost and convenience. This is done by making Mg 17 Al 12 dissolved into α-Mg matrix and then precipitated once again.Semisolid metal (SSM) processing is recognized as Abstract:The microstructure and hardness of rheo-forming AZ91-Y alloy before and after solution treatment (ST) have been investigated by means of optical microscope (OM), scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Vickers. The experimental results showed that the β-Mg 17 Al 12 phase of alloy was nearly dissolved after ST for 5 min. With the increasing of ST duration to 28 h, both the primary and secondarily solidified α-Mg grains faded away. At the same time, the alloy exhibited a much smoother surface due to the diffusion of solute atoms (Al). During ST, the thermal stable phase of Al 2 Y produced by ultrasonic vibration retained its size and morphology. As the ST duration was increased, the alloy hardness decreased sharply at first, and then gradually reached a minimum level. an outstanding technique for Mg alloys. Its advantages are compared to the conventional die casting processes, including the potential of producing near-net shape and high-integrity components, low processing temperature that resolved the problem of oxidation, and effective burning in Mg alloys processing [8] . Several works have studied the microstructure evolution of AZ91D alloy fabricated by SSM processing during heat treatment [9][10] , but few studies related to the SSM processed Mg-Al series alloys containing RE have been reported. Also, it is well known that different casting processes will result in a variation of the microstructure, which could influence dissolution and precipitation kinetics of Mg 17 Al 12 during subsequent heat treatment. In this present study, solution treatment (ST) at 410 °C was used to process a rheo-forming AZ91-Y alloy. The aim was to detail the alloy's microstructure and hardness before and after ST, and to acquire the appropriate solution duration for subsequent aging treatment. The effect of RE (Y) on kinetics of Mg 17 Al 12 dissolution and the effect of the rheo-forming technique on alloy composition homogenization were also analyzed.

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Section: As-cast Microstructurementioning

confidence: 71%

Effect of solution treatment on microstructure and hardness of rheo-forming AZ91-Y alloy

2016

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“…Turen [9] investigated that, 0.5 wt.% Sn addition to AZ91 alloy, transformed the lamellar eutectic structure into fully divorced β eutectic, forming fine Mg 2 Sn phase that distributed throughout α-Mg matrix, which could block the movement of dislocation by Orowan looping. Li et al [10] also reported that Sn addition could suppress the formation of discontinuous precipitation at grain boundary in aged AZ91D alloy and there was no discontinuous precipitation up to 2.0 wt.% Sn addition. Moreover, Sn is an inexpensive alloying element that can strengthen the AZ91 alloy by solid solution hardening and precipitation strengthening by the formation of new intermetallic Mg 2 Sn phase, besides it has a high hydrogen voltage that can improve the corrosion resistance [9,11].…”

Section: Introductionmentioning

confidence: 94%

Mechanical characterization and corrosion behavior of newly designed Sn and Y added AZ91 alloy

et al. 2015

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“…The amount of β phase presents in HPDC Mg components can have a significant impact on the material properties and kinetics of dissolution during solution treatment. Some analytical [19,20] and numerical [21,22] models for second phase dissolution kinetics have been developed, but there are few systematic, quantitative studies on the HPDC Mg alloys.…”

Section: Introductionmentioning

confidence: 99%

An ICME Method for Predicting Phase Dissolution During Solution Treatment in Advanced Super Vacuum Die Cast Magnesium Alloys

Yao

Berman

Allison

2020

Integr Mater Manuf Innov

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An integrated computational materials engineering (ICME) methodology was applied in this study to systematically and quantitatively study the second phase dissolution kinetics during the solution treatment process of a high pressure die cast magnesium sample. The study was conducted on Mg-9 wt% Al, Mg-5 wt% Al, and Mg-11 wt% Al binary alloys after isothermal solution treatments ranging from 380 to 420 °C. The experimental measurements revealed an exponential decrease of the volume fraction of the second β-phase (Mg 17 Al 12) during the solution treatment. A CALPHAD-based computational tool (Thermocalc DICTRA Diffusion Module) was used to simulate the dissolution process. In this study, measurements from as-cast samples were used as input parameters to improve the accuracy of the predicted results. An analytical, physics-based micro-model, based on the Johnson-Mehl-Avrami type equation, was also applied to study the dissolution kinetics. Both the simulation and micro-model quantitatively agree with the experimental results at all solution treatment temperatures. Calibration and verification of a few input parameters help to understand the assumptions made in the modeling, improve the accuracy of the prediction, and can be applicable in different Mg-Al binary alloys. Adopting such an ICME methodology for modeling development and verification in predicting the dissolution kinetics during solution treatment will allow for more rapid optimization of solution treatments procedures to be used in industrial applications.

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Dissolution of Eutectic β-Mg17Al12 Phase in Magnesium AZ91 Cast Alloy at Temperatures Close to Eutectic Temperature

Cited by 31 publications

References 24 publications

Effect of solution treatment on microstructure and hardness of rheo-forming AZ91-Y alloy

Effect of solution treatment on microstructure and hardness of rheo-forming AZ91-Y alloy

Mechanical characterization and corrosion behavior of newly designed Sn and Y added AZ91 alloy

An ICME Method for Predicting Phase Dissolution During Solution Treatment in Advanced Super Vacuum Die Cast Magnesium Alloys

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