Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments

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Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments. / Xiao, Lei; Yang, Guangyu; Ma, Jiaqi; Qin, He ; LI, Jiehua; Jie, Wanqi.

in: Materials characterization, Jahrgang 168, 110516, 10.2020.

Publikationen: Beitrag in FachzeitschriftArtikelForschung(peer-reviewed)

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@article{cdbaf9d8c3f5457e8de039548b31f5c9,
title = "Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments",
abstract = "Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments were systematically investigated using SEM and TEM as well as tensile testing. It was found that the microstructure of the as-cast alloy consisted of α-Mg matrix, net-like eutectic compounds (α-Mg + Mg 3 (Gd, Zn)), cubic GdH 2 phases and lamellar 14H LPSO phases. After solution treated at 515 °C for 24 h, two different cooling processes were used to elucidate the effect of cooling rates on the precipitation microstructure. With a hot water quenching, those secondary phases were completely dissolved. Instead, grey-like patches were observed within the α-Mg matrix, which were proposed to be rod-like Zn 2Zr 3 phases around the α-Zr particle. In contrast, with a furnace cooling, the formation of 14H LPSO and several cubic Mg 3 (Gd, Zn) phases was observed. Furthermore, after hot water quenching, the subsequent ageing treatment parameters were also optimized to be 225 °C for 48 h. In the peak-aged condition, a denser and uniform distribution of basal precipitates γ″ and several basal precipitates γ′ together with Zn 2Zr 3 and ZnZr 2 phases were observed. The samples after the solution treatment (for both hot water quenching and furnace cooling) showed a much higher ductility than the as-cast alloy, while the tensile yield strength (TYS) and ultimate tensile strength (UTS) remained unchanged. After the peak-ageing, a significant increase in the TYS and UTS but a great loss in ductility was observed. In the as-cast alloy, the initiation of microcracks occurred from the net-like eutectic compounds, which was believed to be one of the most important reasons for the tensile fracture, and showed a co-existence of intergranular and transgranular fracture behavior. After the solution treatment, with a hot water quenching, the fracture can be mainly related with failures along contraction twins, and then showed a transgranular fracture behavior. While, with a furnace cooling, due to the presence of the kinked 14H LPSO phases, the fracture was caused by the broken of 14H LPSO phases, and then lead to a transgranular fracture. The peak-aged alloy exhibited a brittle intergranular fracture, which can be related with failures along soft precipitation free zones (PFZs). ",
keywords = "Heat treatment, Magnesium alloy, Mechanical properties, Rare earth elements, Tensile fracture behavior",
author = "Lei Xiao and Guangyu Yang and Jiaqi Ma and He Qin and Jiehua LI and Wanqi Jie",
year = "2020",
month = oct,
doi = "10.1016/j.matchar.2020.110516",
language = "English",
volume = "168",
journal = "Materials characterization",
issn = "1044-5803",
publisher = "Elsevier",

}

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TY - JOUR

T1 - Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments

AU - Xiao, Lei

AU - Yang, Guangyu

AU - Ma, Jiaqi

AU - Qin, He

AU - LI, Jiehua

AU - Jie, Wanqi

PY - 2020/10

Y1 - 2020/10

N2 - Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments were systematically investigated using SEM and TEM as well as tensile testing. It was found that the microstructure of the as-cast alloy consisted of α-Mg matrix, net-like eutectic compounds (α-Mg + Mg 3 (Gd, Zn)), cubic GdH 2 phases and lamellar 14H LPSO phases. After solution treated at 515 °C for 24 h, two different cooling processes were used to elucidate the effect of cooling rates on the precipitation microstructure. With a hot water quenching, those secondary phases were completely dissolved. Instead, grey-like patches were observed within the α-Mg matrix, which were proposed to be rod-like Zn 2Zr 3 phases around the α-Zr particle. In contrast, with a furnace cooling, the formation of 14H LPSO and several cubic Mg 3 (Gd, Zn) phases was observed. Furthermore, after hot water quenching, the subsequent ageing treatment parameters were also optimized to be 225 °C for 48 h. In the peak-aged condition, a denser and uniform distribution of basal precipitates γ″ and several basal precipitates γ′ together with Zn 2Zr 3 and ZnZr 2 phases were observed. The samples after the solution treatment (for both hot water quenching and furnace cooling) showed a much higher ductility than the as-cast alloy, while the tensile yield strength (TYS) and ultimate tensile strength (UTS) remained unchanged. After the peak-ageing, a significant increase in the TYS and UTS but a great loss in ductility was observed. In the as-cast alloy, the initiation of microcracks occurred from the net-like eutectic compounds, which was believed to be one of the most important reasons for the tensile fracture, and showed a co-existence of intergranular and transgranular fracture behavior. After the solution treatment, with a hot water quenching, the fracture can be mainly related with failures along contraction twins, and then showed a transgranular fracture behavior. While, with a furnace cooling, due to the presence of the kinked 14H LPSO phases, the fracture was caused by the broken of 14H LPSO phases, and then lead to a transgranular fracture. The peak-aged alloy exhibited a brittle intergranular fracture, which can be related with failures along soft precipitation free zones (PFZs).

AB - Microstructure evolution and fracture behavior of Mg-9.5Gd-0.9Zn-0.5Zr alloy subjected to different heat treatments were systematically investigated using SEM and TEM as well as tensile testing. It was found that the microstructure of the as-cast alloy consisted of α-Mg matrix, net-like eutectic compounds (α-Mg + Mg 3 (Gd, Zn)), cubic GdH 2 phases and lamellar 14H LPSO phases. After solution treated at 515 °C for 24 h, two different cooling processes were used to elucidate the effect of cooling rates on the precipitation microstructure. With a hot water quenching, those secondary phases were completely dissolved. Instead, grey-like patches were observed within the α-Mg matrix, which were proposed to be rod-like Zn 2Zr 3 phases around the α-Zr particle. In contrast, with a furnace cooling, the formation of 14H LPSO and several cubic Mg 3 (Gd, Zn) phases was observed. Furthermore, after hot water quenching, the subsequent ageing treatment parameters were also optimized to be 225 °C for 48 h. In the peak-aged condition, a denser and uniform distribution of basal precipitates γ″ and several basal precipitates γ′ together with Zn 2Zr 3 and ZnZr 2 phases were observed. The samples after the solution treatment (for both hot water quenching and furnace cooling) showed a much higher ductility than the as-cast alloy, while the tensile yield strength (TYS) and ultimate tensile strength (UTS) remained unchanged. After the peak-ageing, a significant increase in the TYS and UTS but a great loss in ductility was observed. In the as-cast alloy, the initiation of microcracks occurred from the net-like eutectic compounds, which was believed to be one of the most important reasons for the tensile fracture, and showed a co-existence of intergranular and transgranular fracture behavior. After the solution treatment, with a hot water quenching, the fracture can be mainly related with failures along contraction twins, and then showed a transgranular fracture behavior. While, with a furnace cooling, due to the presence of the kinked 14H LPSO phases, the fracture was caused by the broken of 14H LPSO phases, and then lead to a transgranular fracture. The peak-aged alloy exhibited a brittle intergranular fracture, which can be related with failures along soft precipitation free zones (PFZs).

KW - Heat treatment

KW - Magnesium alloy

KW - Mechanical properties

KW - Rare earth elements

KW - Tensile fracture behavior

UR - http://www.scopus.com/inward/record.url?scp=85088752324&partnerID=8YFLogxK

U2 - 10.1016/j.matchar.2020.110516

DO - 10.1016/j.matchar.2020.110516

M3 - Article

VL - 168

JO - Materials characterization

JF - Materials characterization

SN - 1044-5803

M1 - 110516

ER -