LetterThe solution and room temperature aging behavior of Mg–9Li–xAl(x = 3, 6) alloys
Introduction
During the past decade, increasing attention has been paid to Mg alloys for their applications in automobile, aviation and electronic industries [1], [2]. As the lightest metallic engineering materials, Mg–Li alloys have some impressive advantages, such as high specific strength and stiffness, excellent electromagnetic shielding and damping properties [3]. Mg–Li alloy has a density of 1.3–1.6 g/cm3, which is twenty-five percent lighter than that of conventional magnesium alloys [4], [5]. Moreover, when Li content is between 5.7 and 10.3 mass%, Mg–Li alloys possess two-phase structures that consist of the α-Mg (hcp) and β-Li (bcc) phases at room temperature [6], [7], [8]. However, Mg–Li alloys have the drawbacks of low strength, poor corrosion resistance, and thermal instability, which are not beneficial for their application. To overcome these drawbacks, various third elements (such as Al, Zn) have been added to Mg–Li alloy systems [9], [10], [11], [12], [13], [14].
From previous works, it is known that Mg–Li–Al alloys are typically aging hardening alloys at room temperature (RT). RT aging behavior of Mg–(11–14)Li–Al alloys (with the matrix of β-Li) has been reported by many authors [15], [16]. As for the Mg–5Li–3Al–2Zn alloy (with the matrix of α-Mg), it has been reported that the Ag addition can cause the formation of θ-MgLi2Al and reduce the amount of AlLi, resulting the better aging hardening [17]. In this paper, Mg–9Li–xAl alloys (with the matrix of α-Mg and β-Li) with a high Al content (3 and 6 wt.%) were prepared, and the solution and RT aging behavior of the alloys were investigated.
Section snippets
Materials preparation
Two alloys with nominal compositions of Mg–9Li–3Al(LA93) and Mg–9Li–6Al (LA96) were prepared by melting purity metals, magnesium(99.95 wt.%), lithium (99.90 wt.%), pure aluminum (99.90 wt.%), in an induction melting furnace under the ambient of argon gas. After melting, the melt was poured into a steel mold to obtain as-cast specimens. Then the specimens were cut into small ones and were solid solution-treated for 1 h under an argon atmosphere. The solution temperatures are 350 and 400 °C,
Microstructure of as-cast alloys
Fig. 1 shows the light microstructure of as-cast Mg–9Li–xAl(x = 3, 6) alloys. It reveals that Mg–9Li–xAl alloys are mainly composed of α-Mg and β-Li. In LA93, the shape of α phase (white) is block-like shape, and there exist a few small spheric particles inside the β phase (gray), as shown in Fig. 1a. In LA96 (Fig. 1b), both block-like α phase (white) and block-like compounds (black) can be seen. In more details, some white particles distributes evenly in the β phase (gray).
The XRD patterns of
Conclusions
In the as-cast alloys, Mg–9Li–3Al is composed of α(Mg), β(Li) and AlLi, and Mg–9Li–6Al is composed of α(Mg), β(Li), AlLi and θ(MgLi2Al). After solution treatment, AlLi phase is completely solutionized into the matrix, while the θ phase in LA96 alloy cannot be fully dissolved in the matrix. In the RT aging process, plentiful AlLi phase precipitates from matrix and aggregates together after 48 h. The morphology of AlLi phase is small spheric particles in β phase in as-cast alloy. However, in RT
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 51001034), the Fundamental Research funds for the Central Universities (HEUCF201210004), the Research Fund for the Doctoral Program of Higher Education (20092304120020) and the Project for Heilongjian Province General Institution of Higher Education Young Scientific Key Teacher (1252G018).
References (17)
- et al.
Mater. Sci. Eng. A
(2010) - et al.
Mater. Sci. Eng. A
(1999) - et al.
Scr. Mater.
(1998) - et al.
Mater. Sci. Eng. A
(2009) Mater. Sci. Forum
(2005)- SAE International TM. Magnesium for automotive components. Warrendale (PA), Society of Automotive Engineers,...
- et al.
Magnesium and Magnesium Alloys-ASM Specialty Handbook
(1999) - et al.
Rev. Adv. Mater. Sci.
(2010)
Cited by (60)
Achieving ultrahigh specific strength of an ultrafine grained Mg–9Li–1Al alloy via the combined processing of ECAP with repeated annealing and rolling
2023, Journal of Materials Research and TechnologyVariable precipitation behaviors of Laves phases in an ultralight Mg-Li-Zn alloy
2023, Journal of Magnesium and AlloysInfluence of various initial microstructures on microstructure and mechanical property of ECAP processed Mg-8.4Li-3.58Al-0.36Si-0.05Ti-0.01B alloys
2023, Materials Science and Engineering: AHot deformation behavior of Mg-5Li-3Al-2Zn-0.2Zr alloy based on constitutive analysis, processing map, and microstructure evolution
2023, Journal of Alloys and CompoundsLithium mapping in a Mg-9Li-4Al-1Zn alloy using electron energy-loss spectroscopy
2023, Journal of Magnesium and AlloysMicrostructure and mechanical properties of heat-treated Mg–6.2Li–3.5Al–3Y alloy
2022, Materials Science and Engineering: ACitation Excerpt :Besides, the solid solubility of aluminum in magnesium is large, and the solid solubility changes significantly as the temperature decreases. Therefore, the effect of solid solution strengthening is obvious [24–26]. Li et al. [27] found that the microhardness of Mg–35Li alloy increased by 50% to 1.63 GPa with the addition of Al element.