TY - GEN
T1 - CALPHAD Modeling and Microstructure Investigation of Mg–Gd–Y–Zn Alloys
AU - Meier, Janet
AU - Caris, Josh
AU - Luo, Alan A.
N1 - Publisher Copyright:
© 2020, The Minerals, Metals & Materials Society.
PY - 2020
Y1 - 2020
N2 - In this study, CALPHAD (CALculation of PHAse Diagrams) modeling was used to design and optimize Mg–Gd–Y–Zn alloys containing long period stacking order (LPSO) phases. The selected compositions were evaluated using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction to identify major phases and determine their area fractions. It was seen in as-cast samples that a blocky LPSO 14H phase formed at the grain boundaries while a filament-type LPSO 14H formed in the Mg grains. As the rare earth (RE) and Zn concentrations increased, eutectic Zn-rich intermetallics and more of the RE-rich blocky LPSO formed along grain boundaries. After annealing, an increase in the Zn-rich intermetallic area fraction, decrease in bulky LPSO area fraction, and increase in filament-type LPSO were observed. In higher alloyed samples, a Zn- and Y-rich phase was observed that was not consistent with the predicted or reported phase. These results indicate the present CALPHAD databases well represent the LPSO 14H formation in the Mg–Gd–Y–Zn system studied and can be used to tailor the microstructure to potentially improve the strength and ductility in these alloys. Further investigation is needed to determine if the existing reliably databases model the other secondary phases.
AB - In this study, CALPHAD (CALculation of PHAse Diagrams) modeling was used to design and optimize Mg–Gd–Y–Zn alloys containing long period stacking order (LPSO) phases. The selected compositions were evaluated using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction to identify major phases and determine their area fractions. It was seen in as-cast samples that a blocky LPSO 14H phase formed at the grain boundaries while a filament-type LPSO 14H formed in the Mg grains. As the rare earth (RE) and Zn concentrations increased, eutectic Zn-rich intermetallics and more of the RE-rich blocky LPSO formed along grain boundaries. After annealing, an increase in the Zn-rich intermetallic area fraction, decrease in bulky LPSO area fraction, and increase in filament-type LPSO were observed. In higher alloyed samples, a Zn- and Y-rich phase was observed that was not consistent with the predicted or reported phase. These results indicate the present CALPHAD databases well represent the LPSO 14H formation in the Mg–Gd–Y–Zn system studied and can be used to tailor the microstructure to potentially improve the strength and ductility in these alloys. Further investigation is needed to determine if the existing reliably databases model the other secondary phases.
KW - Alloy development
KW - CALPHAD
KW - Long period stacking order (LPSO)
KW - Magnesium alloys
KW - Microstructure
UR - http://www.scopus.com/inward/record.url?scp=85081653410&partnerID=8YFLogxK
U2 - 10.1007/978-3-030-36647-6_12
DO - 10.1007/978-3-030-36647-6_12
M3 - Conference contribution
AN - SCOPUS:85081653410
SN - 9783030366469
T3 - Minerals, Metals and Materials Series
SP - 61
EP - 69
BT - Magnesium Technology 2020
A2 - Jordon, J. Brian
A2 - Miller, Victoria
A2 - Joshi, Vineet V.
A2 - Neelameggham, Neale R.
PB - Springer
T2 - Magnesium Technology Symposium held at the 149th Annual Meeting and Exhibition, TMS 2020
Y2 - 23 February 2020 through 27 February 2020
ER -