Tensile mechanical properties and failure behaviors with the ductile-to-brittle transition of the α + β-type Mg–Li–Al–Zn alloy

doi:10.1016/j.scriptamat.2009.08.037

Scripta Materialia

Volume 61, Issue 12, December 2009, Pages 1141-1144

https://doi.org/10.1016/j.scriptamat.2009.08.037 Get rights and content

This study focuses on investigating the tensile mechanical properties and failures of the α + β two-phase Mg–10.3Li–2.4Al–0.7Zn (wt.%) alloy at testing temperatures from −25 to 250 °C. The tensile stresses and elongations are sensitive to the deformation temperatures. A significant ductile-to-brittle transition temperature is recognized at about 50 °C. The failures, which occurred from brittle fracture with evident cleavage to ductile dimpled ruptures, is related to the transition of slip systems with increasing temperatures and the cavitation between α/β-phase interface.

References (29)

B.L. Mordike et al.
Mater. Sci. Eng. A
(2001)
N. Saito et al.
Scripta Mater.
(1997)
Z. Drozd et al.
J. Alloy Compd.
(2004)
T.C. Chang et al.
Mater. Lett.
(2006)
M.C. Lin et al.
Scripta Mater.
(2007)
D.K. Xu et al.
Scripta Mater.
(2007)
S.P. Lynch et al.
Acta Mater.
(2001)
A.M. Russell et al.
Scripta Mater.
(1998)
G.S. Song et al.
Mater. Sci. Eng. A
(2004)
W.A. Counts et al.
Acta Mater.
(2009)

D.H. Kim et al.

Scripta Metall. Mater.

(1994)

D.H. Bae et al.

Acta Mater.

(2002)

R. VanFleteren

Adv. Res. Process.

(1996)

H. Haferkamp et al.

Mater. Trans.

(2001)

Cited by (45)

Effect of icosahedral phase formation on the stress corrosion cracking (SCC) behaviors of the as-cast Mg-8%Li (in wt.%) based alloys
2024, Journal of Magnesium and Alloys
Through exploring the stress corrosion cracking (SCC) behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution, it revealed that the SCC susceptibility index (I_SCC) of the Mg-8%Li alloy was 47%, whilst the I_SCC of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%. Surface, cross-sectional and fractography observations indicated that for the Mg-8%Li alloy, the α-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process. With regard to the Mg-8%Li-6%Zn-1.2%Y alloy, the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li and α-Mg/β-Li, and the preferential propagation paths were the I-phase/β-Li and α-Mg/β-Li interfaces. Moreover, the SCC of the two alloys was concerned with hydrogen embrittlement (HE) mechanism.
Achieving ultra-high stiffness by solidifying and precipitating micro-compounds in HCP/BCC dual matrix of a new Mg-Li alloy
2023, Journal of Alloys and Compounds
One of the major obstacles restricting the wide applications of Mg alloys is their low Young's modulus at ∼45 GPa, which is uncompetitive to Al alloy over 60 GPa. To resolve this issue, we proposed a new strategy of designing ultra-light Mg-Li alloys by employing the microscale compounds in both HCP and BCC grains to achieve high Young’s modulus. HCP or BCC alone cannot achieve a high modulus due to the segregation of solutes at the grain boundaries and the formation of brittle intermetallics in the interdendritic region. We designed chemistry that is so perfect to arrest the excess solutes inside the BCC matrix during solidification and engulf pre-solidified rare earth particles by HCP primary grains which have such a lean chemical composition that has almost no segregation. During solution heat treatment, the dissolution of solutes pushes the BCC boundary towards HCP grains by Ostwald ripening (BCC structures are interconnected but the HCP structures are isolated). During low-temperature aging heat treatment, nucleation of HCP structure on the rare earth particles inside the BCC grain is found, degrading the strength. Therefore, a novel Mg-Li-Al-Zn-Y-Mn-Gd (LAZWMV) alloy with a very high modulus was designed which reaches Young's modulus as high as 61.4 GPa. Micro-compounds (AlLi and Al-X) with average equivalent diameters of 3.76 µm and 6.55 µm were quantified in 3D using X-ray computed tomography and nanoindentation tests for establishing the microstructure-modulus correlation. The influence of Li addition on Mg-Mg was calculated by DFT calculations and the mechanism of modulus improvements has been proposed.
Microstructure and mechanical properties of heat-treated Mg–6.2Li–3.5Al–3Y alloy
2022, Materials Science and Engineering: A
To further improve the mechanical properties of Mg–Li alloys, the microstructure evolution and mechanical properties of Mg–6.2Li–3.5Al–3Y alloy after different heat treatment processes (holding at 250 °C, 300 °C, 350 °C and 400 °C for 30 min, 60 min and 120 min, respectively) have been investigated in this study. It is found that the Mg₂Y eutectic disappears after heat treatment, and the volume fraction of Al₂Y precipitated phase decreases first and then increases with increasing heat treatment time. In addition, The tensile test results reveal that the tensile strength of the alloy increases first and then decreases with the increase of heat treatment time. The tensile strength and ductility of the alloy reach 182 MPa and 12.7%, respectively, after heat treatment at 400 °C for 30 min, which are 35.8% and 36.5% higher than those of as-cast alloy. The evolution of Mg₂Y eutectic and Al₂Y phase during heat treatment processes at different time and temperatures are analyzed in detail. It can be concluded that the tensile strength of the alloy is improved by the combined effects of precipitation hardening due to the formation of Al₂Y phase, and the solid solution strengthening due to the decomposition of Mg₂Y eutectic and Al₂Y precipitated phase.
Tailoring the microstructure and texture of a dual-phase Mg–8Li alloy by varying the rolling path
2022, Materials Science and Engineering: A
Dual-phase Mg–Li alloys exhibit better formability than conventional Mg alloys. However, conventional processing methods, such as rolling and extrusion, usually result in a lamellar structure, which will generate a strong planar anisotropy. In the present study, an as-extruded dual-phase Mg-8Li plate was rolled along two different directions, extrusion direction (ED-rolling) and transverse direction (TD-rolling), with the aim to investigate the effect of rolling path on the microstructure, texture and in-plane mechanical anisotropy. The results show that the lamellar α+β structures in the initial plate well remained after 20% or 50% ED-rolling and subsequent annealing at 250 °C for 4 h. In contrast, this lamellar structure completely disappears after TD-rolling and subsequent annealing. The basal poles of grains close to the TD in α phase in the initial plate slightly rotate from TD towards the normal direction (ND) during ED-rolling, while are largely parallel to the ND after TD-rolling. The variation of rolling path hardly alters the texture of β phase. For both α and β phases, annealing does not change the type of texture, only reduce the maximum intensity of texture. The mechanisms for texture evolution during rolling were studied using visco-plastic self-consistent (VPSC) simulations. It is shown that the main texture features of rolled plates are determined by the activated deformation modes in each phase, while α/β phase boundaries will retard the texture evolution. After ED-rolling, there is an obvious anisotropy in work hardening behavior and elongation for tension along the TD and RD, while this mechanical anisotropy disappears after TD-rolling. The corresponding mechanism were discussed.
Charpy impact behavior and deformation mechanisms of Cr<inf>26</inf>Mn<inf>20</inf>Fe<inf>20</inf>Co<inf>20</inf>Ni<inf>14</inf> high-entropy alloy at ambient and cryogenic temperatures
2022, Materials Science and Engineering: A
Stacking fault energy (SFE) of high- and medium-entropy alloys (HEAs and MEAs) can be tuned by tailoring the constituent. In this work, we prepared a non-equiatomic Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄ HEA with low SFE and investigated the Charpy impact behavior at 298 and 77 K, respectively. The Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄ HEA performs an inverse temperature dependence of absorbed impact energy, in contrast to the slight decrease of the equiatomic CrMnFeCoNi HEA. Detailed microstructural investigation along the cracks reveals that dislocation pilling-up and nano-twinning are the dominant strengthening mechanisms for the Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄ HEA at 298 K and the CrMnFeCoNi HEA at 298 and 77 K. For Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄ HEA at 77 K, except for the enhanced twinning and dislocation storage, additional hexagonal close packed (HCP) structured ε phase transformation also occurred, contributing to the higher strain hardening ability and impact toughness. This study provides experimental evidence for designing HEAs for potential cryogenic applications.
Corrosion behavior characterization of as extruded Mg-8Li-3Al alloy with minor alloying elements (Gd, Sn and Cu) by scanning Kelvin probe force microscopy
2020, Corrosion Science
The effects of Gd, Sn and Cu on the corrosion behavior of as extruded Mg–8Li–3Al (LA83) alloy were characterized by scanning Kelvin probe force microscopy, weight loss, hydrogen evolution, and electrochemical measurements. Result revealed that many Al₂Gd, Mg₂Sn, and AlCuMg particles were discovered in modified alloys, respectively. The combined experimental results of weight loss, hydrogen evolution, and electrochemical analysis indicated that the addition of Gd and Sn improve the corrosion resistance of as extruded LA83 alloy while the addition of Cu weaken its corrosion resistance. The corrosion mechanisms of different elements in as extruded samples were discussed.

View all citing articles on Scopus

View full text

Tensile mechanical properties and failure behaviors with the ductile-to-brittle transition of the α + β-type Mg–Li–Al–Zn alloy

Mater. Sci. Eng. A

Scripta Mater.

J. Alloy Compd.

Mater. Lett.

Scripta Mater.

Scripta Mater.

Acta Mater.

Scripta Mater.

Mater. Sci. Eng. A

Acta Mater.

Scripta Metall. Mater.

Acta Mater.

Adv. Res. Process.

Mater. Trans.