Mg-Li Alloy Research Articles

Effects of graphene-based corrosion inhibition materials on the microstructure and corrosion resistance of Ni-based coating on Mg-Li alloys

Two kinds of layered double hydroxides inhibition materials were synthesized on graphene oxide, and applied to strengthen the Ni-based coating on Mg-Li alloy. The composition and release properties of corrosion inhibition materials were studied. The formation of passivated film and the corrosion resistance mechanism of coating were summarized. The results show that two kinds of corrosion inhibition materials had good release properties. The addition of corrosion inhibition materials was helpful to form Ni-based composite coatings with fine and dense cell clusters, which strengthened the corrosion resistance of the coating, especially for a long time.

Electrically conductive and corrosion resistant coating on Mg[sbnd]Li alloys, Part I: Chemical conversion coating

MgLi alloys are one of the lightest structural materials, but suffer from severe corrosion due to the hyperactivity of Mg and Li. In this work, an electrically conductive and corrosion-resistant chemical conversion coating was fabricated on a duplex MgLi alloy LA103Z by two different routes: the first route using a conventional immersion treatment (Im-PCCs); and the second route using a brushing conversion treatment (Br-PCCs). Results demonstrate that chemical composition of conversion coatings remained, but surface morphology was altered. The Im-PCC depicts many lamellar CaHPO4 when the immersion time was longer than 60 s. The Br-PCC shows no lamellas on surface till a treatment time of 120 s. These lamellar crystals are detrimental to the electrical contact resistance (ECR), and the ECR for the Br-PCC was one order of magnitude lower than that for the Im-PCCs. Corrosion resistance for Br-PCCs, however, was slightly lower than Im-PCCs.

When mussel meets lotus leaf and pitcher plant: A combinational biomimetic strategy for Mg-Li corrosion inhibition

Magnesium-lithium alloys hold immense promise as lightweight structural materials due to combination of unique properties. However, their widespread application is hindered by the inherent poor corrosion resistance. This research presents a novel and cost-effective approach to address this obstacle by utilizing metal-phenol networks inspired by mussel as surface modifiers. These networks facilitate the deposition of nanoparticle on magnesium-lithium (Mg-Li) alloys through chemical reactions between phenolic groups and metal ions. The resulting surface is further enhanced by spray-coating a sheet-like biomimetic superhydrophobic surface (SHS) of alkyl-ketone dimer (AKD), subsequently followed by lubricant infusion with dimethylsilicone oil to create a slippery liquid-infused porous surface (SLIPS). Characterization using multiple techniques confirms the chemical composition and morphology of the modified surface, which significantly improves the corrosion resistance of the magnesium-lithium alloy. Importantly, scanning Kelvin probe measurements reveal that SHS and SLIPS enhance the atmospheric corrosion resistance of the material. Further validation in 3.5 wt% NaCl solution demonstrates remarkable effectiveness of SLIPS. During the initial stages of immersion, the impedance magnitude |Z|0.01 Hz for SLIPS reaches a remarkable 3.78 × 107 Ω·cm2, exceeding those of the SHS, TA-LA141, and bare LA141 by 3, 3, and 6 orders of magnitude, respectively. This performance persists even after long-term immersion, with the SLIPS coating still exhibiting an impedance value one order of magnitude higher than the SHS after extended exposure. These results establish the effectiveness of SLIPS as a promising candidate for significantly upgrading the corrosion resistance of Mg-Li alloy, paving the way for their broader utilization in demanding fields.

Strengthening mechanism and interaction between nano precipitates and defects in wrought Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd alloys

Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd (x = 2.4, 6) alloys were subjected to multi-directional forging (MDF). The β1 coherent phase and β incoherent phase precipitated during the MDF process significantly improve the properties of the alloy. The results show that the orientation relationship between the β1 phase and the matrix is 022β1∥0002α and 111β1∥12¯10α.When the dislocations cut through the β1 phase, the {111} 〈110〉 slip system of the β1 phases is activated, forming anti-phase boundaries (APBs) by directional motion in the <110> direction, which provides strengthening effects. The APB structure leads to the increase of system energy, deformation resistance, and yield strength. Besides, the activation of the β1 phases slip system makes the alloys exhibit satisfactory plasticity and toughness. After MDF at 350 °C, Mg-5Li-1Zn-0.5Ag-0.5Zr-2.4Gd alloy has a yield strength of 270 MPa, a tensile strength of 295 MPa, and an elongation of 12.7%, respectively. The results are beneficial for the design and manufacture of high-performance MgLi alloys.

Effect of Corrosion Inhibitor Pyrovanadate Ions on Microstructure and Corrosion Resistance of MgAl Layered Double Hydroxide Films on LA43M Mg-Li Alloy

In order to explore the effect of corrosion inhibitor modification on the microstructure and corrosion resistance of MgAl layered double hydroxide (LDH) film on LA43M Mg-Li alloy, the LDH films were successfully obtained by ion exchange method at different hydrothermal temperatures. Microstructure of the MgAl LDH films with anion intercalation were characterized by SEM, EDS and XRD, and the corrosion resistance of the films were tested by EIS, polarization curve and hydrogen evolution experiments. The results showed that the modified LDH nanosheets are larger in size, denser and slightly thicker than that of MgAl LDH film. Electrochemical tests and hydrogen precipitation experiments demonstrated that the corrosion inhibitor modified LDH films can further enhance the corrosion resistance of the film. The LDH prepared at 60°C has the most uniform density and the maximum thickness. It has the lowest Icorr(1.754×10−8 A.cm2) and the most positive Ecorr(−1.147 V). Furthermore, it showed the best corrosion resistance in 3.5 wt% NaCl solution.

Effect of solid solution treatment on biomedical Mg-Li alloy with high Zn content

Microstructure, mechanical strength, corrosion resistance, and osteogenesis of as-cast Mg-11 wt% Li-12 wt% Zn alloy were investigated before and after solid solution treatment. Massive MgLiZn and MgLi2Zn phases were formed in the as-cast sample, resulting in micro-galvanic corrosion and high corrosion rate. After the solid solution treatment, the lath-shaped α-Mg phase remained in the β-Li matrix, whereas the large MgLiZn and MgLi2Zn phases dissolved in it, resulting in enhanced the corrosion resistance. Moreover, the yielding strength of the as-cast sample was improved from 136 to 260 MPa after treatment. In addition, the solid solution-treated Mg-Li-Zn exhibited improved induction of the alkaline phosphatase activity and osteogenesis-related gene expression in rBSMCs, confirming its promising potential for orthopedic applications.

Investigation of Wear Properties and Corrosion Resistance of Electrodeposited Ni-P-PTFE Nanocomposite Coating on Mg-Li alloy

Ni-P-polytetrafluorethylene nanocomposite coatings based on Mg-Li alloy were successfully prepared by utilizing electrodeposition method. The nanocomposite coatings were investigated employing scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The microstructure and composition of the coating were studied by friction, wear and corrosion tests. The experimental results reveal that when the concentration of PTFE is 3 g / L, deposition temperature is 70 °C, current density is 2 A/dm2, and pH of the plating solution is approximately 5.5, a uniform and dense Ni-P-PTFE nanocomposite coating is formed on Magnesium alloy substrate, and it exhibited a low coefficient of friction (∼1.5) and superior abrasion resistance. The co-deposition of PTFE particles can effectively reduce the friction coefficient and wear rate, and the wear mechanism is characteristic cutting wear. Under artificial seawater conditions, the experiments have demonstrated that the nanocomposite material possesses a corrosion current density of 3.9×10-5 A/cm2.

Fabrication of biodegradable superhydrophobic Zn-Fe coating on ultra-light Mg-Li alloy

As a typical biodegradable and biocompatible light metal, magnesium (Mg) and its alloys exhibit significant prospects for various applications, especially in biomedical materials. Unfortunately, their actual application fields have been restricted by too fast degradation/corrosion rate. Both zinc (Zn) and iron (Fe) are biodegradable and biocompatible but stabler thermodynamically. It's one of the considerable refreshing strategies for controlling the degradation rate of Mg substrate by constructing a ZnFe coating with superhydrophobicity on it. However, it's challenging and rarely reported due to the high chemical reactivity of Mg. This study reports the successful in-situ synthesis of ZnFe coatings with hierarchical micro-/nano-scale structures and superhydrophobicity on ultra-light MgLi alloy by employing an innovative weak alkaline aqueous bath followed by simple chemical modification. Their micromorphology, chemical and phase compositions as well as surface wettability were comprehensively analyzed by FE-SEM, EDS, XRD, XPS, FT-IR, and a contact angle measuring instrument. Furthermore, the degradation behavior of the typical samples was evaluated by modern electrochemical measurement technology. The results revealed that the coating comprised dense micro-papillary structures and nanosheets, exhibiting a static contact angle of droplets up to 161.5° and a sliding angle of 3.0°. In addition, the obtained sample demonstrated a significantly reduced degradation rate compared to the bare magnesium alloy.

The growth and corrosion resistance of MgAl layered double hydroxide films on the surface of LA43M Mg-Li alloy

ABSTRACT To investigate the effect of hydrothermal reaction time on the structure and properties of layered double hydroxides (LDH) films on the surface of Mg alloys, LDH films with different time (12, 18, 24, 30, 36 h) were prepared on the surface of LA43M Mg-Li alloy by an in-situ hydrothermal method. The morphology and phase structure of the film were studied by SEM, XRD and FT-IR, and the corrosion resistance of the film was investigated by electrochemical tests, hydrogen precipitation experiments and immersion tests. In addition, the growth mechanism and corrosion resistance mechanism of the LDH film were analysed. It was found that with longer hydrothermal reaction time, the density and thickness of the film were improved. However, excessive prolongation of hydrothermal time leads to poor film density. The hydrogen precipitation experiment showed that the corrosion rate of LDH-24 h is the smallest. The self-corrosion current density of the film prepared at 24 h was three orders of magnitude lower than the matrix. The best growth and performance of LDH was achieved at a hydrothermal time of 24 h.

Anti-icing and corrosion resistance of superhydrophobic coatings by precision machining and one-step electrodeposition on Mg-Li alloy

Corrosion induced by ice accumulation of liquid droplets causes property deterioration of metallic materials and economic loss. In this study, three microstructured surfaces were prepared on the surface of Mg-Li alloy using precision machining techniques. Superhydrophobic coatings with contact angles around 160° were then deposited on these microstructured surfaces. This was achieved through a one-step electrodeposition method. The rhombic microstructures demonstrated superior anti-icing behavior compared to the other surfaces. This was evidenced by the delayed freezing time of 187 s. The reason behind this behavior lies in the reduced contact area with cooling droplets and the increased air trapped at the interfaces, acting as an isolation barrier to diminish heat transfer efficiency. In corrosive environments, all the coatings exhibited remarkable corrosion resistance. Specifically, the corrosion current density of these coatings decreased by 2–3 orders of magnitude when compared to the substrate.

Quantifying the influence of microstructure on the corrosion of Mg-Li alloys by using X-ray CT

The microstructure of multi-component Mg-Li alloys played a decisive role in their corrosion properties due to the potential differences between the matrix and the secondary phases. In this study, the effects of secondary phases (AlLi, AlX(Gd, Y, Mn), and Mg2Sn) on the corrosion behavior of Mg-Li alloys have been quantified by using in situ X-ray CT. The microstructure-property correlation was established between the type, morphology, distribution, and dimensions of the secondary phases and the microscopic corrosion behavior. The corrosion parameters, such as average equivalent diameter, distance, number density, and volume fraction of the secondary phases and corrosion pits, were quantified as a function of corrosion time. The dominating secondary phase was identified by combining SKPFM analysis and electrochemical testing, giving quantitative information on corrosion control by designing secondary phases.

Machining-induced residual stress and deformation during Mg–Li alloy thin-walled rib-web parts milling

The deformation of thin-walled parts based on the lightweight Mg–Li alloy materials caused by machining-induced stress is an important factor hindering the further development of lightweight in the aerospace field. Prediction of the machining-induced residual stress is the key to understand the deformation and derive low-stress machining scheme. In this study, the equivalent cutting deformation loads were applied to substitute the strongly coupled thermal-mechanical behavior between the tool and part to realize the prediction of the machining-induced stress and deformation of thin-walled rib-web part under different milling conditions. The local regular and complex rib-web parts share a same deformation mode, both behave as in-plane bending deformation of the machined surface. The low-stress milling scheme of up milling combined with cryogenic cooling obtained based on the local regular four rid-web thin-walled part was applicable to the prediction of the complex Mg-Li alloy disk rib-web part. Compared with the initial scheme, the maximum stress and deformation displacement based on the low-stress scheme were reduced from 80 to 36 MPa and from 0.04060 to 0.00814 mm, respectively. Finally, the effectiveness of low-stress milling scheme were verified based on the milling and measurement experiments of the complex thin-walled disk rib-web part. These results indicate the effectiveness of the modeling method for thin-walled rib-web parts and prove the results obtained based on the local model can be extended and applied to large complex parts with the same structural type.

High-strength Mg-6Li-3Al-0.4Ce alloy fabricated by rotary swaging

Low strength is the key factor that keeps Mg-Li alloys from further applications. Herein, a Mg-6Li-3Al-0.4Ce alloy fabricated via rotary swaging exhibits an ultimate tensile strength of 411 MPa, yield strength of 335 MPa, uniform elongation of 11 %, and specific strength of 258 kN·m·kg-1, respectively. The high yield strength is attributed to the dislocations, twins, and stacking faults (SFs) strengthening contributions. The interactions between the twin and grain boundary enhance the strain-hardening capacity. Moreover, the <c + a> dislocations and soft β-Li phase with sufficient slip systems can effectively relax the stress concentration induced by twin-twin interactions, and therefore improve the ductility.

Effects of Friction Stir Processing on the Microstructure and Mechanical Properties of an Ultralight Mg-Li Alloy

Magnesium–lithium alloys are arguably the lightest metal structural materials but have low strength. In order to increase strength, friction stir processing (FSP) is applied to a hot-rolled Mg-10Li-3Al-3Zn (LA103Z) sheet to study the effects on the microstructure and mechanical properties. In this study, the strengthening mechanisms of various FSP regions of an Mg-Li alloy were clarified by a combination of numerical simulation and experimental method. Based on ANSYS APDL, a finite element model with a moving heat source is established. Rotational speeds of 800, 1000, and 1200 rpm and traverse speeds of 100, 110, and 120 mm/min were used in this research. The simulation results confirm that the influence of the rotation speed on the alloy temperature field is greater than that of the travel speed. The temperature of the processing area increases with an increase in rotation speed and decreases with an increase in travel speed. Then, hot-rolled LA103Z alloy plates are processed by FSP. The correspondence between the numerical simulation and experiment was verified by infrared thermography. The results indicate that FSP decreases the grain size significantly for the dynamic recrystallization and dramatic mechanical crushing of the stirring pin. The α-Mg and AlLi are solid soluted in the β-Li matrix. The tensile strength of the processing zone is 260.67 MPa (1000 rpm, 110 mm/min) versus the 170.47 MPa of the base metal. The SZ has the highest microhardness of 77.8 HV (800 rpm, 120 mm/min) and decreases gradually to the BM. The severe deformation, recrystallization, and solid solution of the α-Mg are important factors contributing to the improved mechanical properties.

Physical Simulation of Medium and Low Temperature Rolling of Mg-Li Alloy Sheet

In this paper, LZ91 magnesium-lithium alloy was taken as the research object. At the rolling temperature of room temperature and 453 K, the plane strain compression physical simulation experiment was carried out on the sample with one pass reduction of 15 % and three passes total reduction of 45 %. After each pass of rolling, the sample was annealed at 503 K for 30 min. Then the effects of different treatment processes on the microstructure of LZ91 magnesium-lithium alloy were studied by metallographic microscope, X-ray diffractometer and scanning electron microscope. The results show that under the same strain, the stress of room temperature rolling is larger than that of 453 K rolling; with the increase of annealing passes, the effect of work hardening gradually weakened. With the increase of rolling amount, the original mechanically mixed ' α ' phase and ' β ' phase will deform along the deformation direction, showing a streamline shape. Rolling at 453 K, the diffraction peak of the sample with 45 % total reduction of three passes changes the most.

Enhancing corrosion resistance in Mg[sbnd]Li alloy through plasma electrolytic oxidation coatings — Exploring the impact of ionic liquids (BmimBF4)

The wide application of MgLi alloys is limited by the poor corrosion resistance, which needs to be improved by surface treatment. Plasma electrolytic oxidation (PEO) method is one of the most promising methods for the formation of oxide coatings on MgLi alloys. However, the conventional PEO technique with high energy consumption causes poor coating compactness and hampers efforts to enhance corrosion resistance. In this study, various concentrations of ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, BmimBF4) are introduced into the concentrated alkaline electrolyte to facilitate the formation of a PEO coating on the surface of LA91 magnesium‑lithium (MgLi) alloy. The influence of BmimBF4 on PEO coatings has been investigated. The results indicate that a concentrated electrolyte significantly lowers the working voltage of PEO, thereby enhancing energy efficiency. Uneven adsorption on the substrate surface, resulting from the low concentration of BmimBF4 (≤20 mL/L) in the electrolyte, induces partial discharge, leading to high surface roughness and the formation of large pores. However, when an excessive amount of BmimBF4 (>20 mL/L) is present, it uniformly adsorbed onto the substrate surface during the initial stage of PEO process, forming a corrosion inhibitor layer. This leads to a consistent discharge on the surface of substrate throughout the entire PEO process, resulting in a reduction in both surface roughness and micropore size. Among these coatings, the one prepared in an electrolyte containing 20 mL/L BmimBF4 exhibits the highest contact angle (66.8° ± 3.8°) and the best long-term corrosion resistance (hydrogen evolution rates <0.02 mL·cm−2·h−1). These properties can be attributed to the physical and chemical adsorption of BmimBF4, which contains hydrophobic long alkyl chains, as well as the maximum thickness with extended discharging channels. This study offers a guiding strategy for further reducing energy consumption and enhancing the corrosion resistance of PEO coatings.

Effects of Nd/YAl2 on aging behavior of Mg-8Li-3Al-RE alloys

In this study, two Mg-Li alloys, LAY831–1.5YAl2p and LAY831–0.4Nd0.3YAl2p, with nice comprehensive mechanical properties were prepared. The differences in microstructure and mechanical properties, such as grain size, phase composition, hardness, tensile strength between the two alloys under different aging temperatures were analyzed comparatively to explore the correlation and micro-mechanism between the fine-tuning of Nd/YAl2 contents and the inhibition of over-aging in multiphase Mg-Li alloys. Our results indicate that both alloys underwent varying levels of β-phase decomposition and precipitation during aging, weakening lattice distortion and causing different magnitudes of strength attenuation. This means strength enhancement as well as lattice distortion caused by solution strengthening of rare earth elements are not stable, significantly affected by the aging temperatures and will gradually be weakened with the aging process. While the external added YAl2 particles, persistently dispersed in the matrix and bear the load, will not decompose during aging, playing a determining role in enhancing stability of the mechanical properties of Mg-Li alloys.

Tailoring the degradation rate of magnesium-lithium alloy with alloying elements of gadolinium and nickel

To explore lightweight degradable materials that are more suitable for fracturing ball, Mg-8Li-4Gd-xNi (x = 0, 0.5, 1, 1.5 wt%) alloys for fracturing ball in petroleum extraction were prepared by vacuum induction melting. The features and formation of long-period stacking ordered (LPSO) doped with gadolinium (Gd) and nickel (Ni) were characterized. And the relationship between the degradation rate of alloys and the structure of LPSO in duplex Mg-Li alloys is investigated. The results show that network 24 R LPSO phase and punctate GdNi3 phase are formed with the addition of Gd and Ni. With the increase of Ni content, the shape of LPSO changes from intermittent network to continuous network and turns into an intermittent network again. The Mg-8Li-4Gd-1.5Ni alloy shows a significant increment in weight loss rate compared with the Mg-8Li-4Gd alloy by 75 times. Atomic force microscope (AFM) results show that the addition of Ni increases the potential difference between the second phase and the β-Li phase from 220 mV to 504 mV. It is difficult for forming LPSO due to higher fault energy when the atomic ratio of Gd to Ni is lower than 4:3, which promotes the LPSO to intermittent network. LPSO and GdNi3 provide higher potentials as cathodes in corrosion, forming a loose and porous corrosion product layer in the alloy. With the increase of Ni content, micro-galvanic corrosion effect is increased which results in a significantly higher corrosion rate of the alloy.

Microstructural evolution and its influence on mechanical and corrosion behaviors in a high-Al/Zn containing duplex Mg-Li alloy after friction stir processing

Ultralight Mg-Li alloys offer promising applications across various fields. Mg-Li alloys enriched with Al and Zn hold theoretical potential for achieving excellent mechanical strength and corrosion resistance. However, the structural and performance characteristics of such Mg-Li alloys, particularly after thermomechanical processing, remain inadequately explored and understood. This study investigated the microstructural evolution of a Mg-9Li-5Al-4Zn alloy after friction stir processing and its consequent effects on the mechanical and corrosion performance. The grain size of the alloy was effectively refined and stabilized during friction stir processing at various heat inputs. The yield strength of the alloy increased by 86.4% after friction stir processing under the highest heat input condition, which was attributed to fine grain strengthening, solid solution strengthening and dispersion strengthening. Concurrently, the alloy experienced a slight decrease in elongation after the friction stir processing. The alloy subjected to friction stir processing with the highest heat input exhibited a minimal corrosion current density of 6.10 × 10−6 A/cm2, which was only 25% of the base metal. The enhanced anti-corrosion properties can be attributed to the dispersion and distribution of precipitated particles induced by friction stir processing, which hindered the micro-galvanic corrosion and promoted the generation of a compact surface film, leading to minimal and uniform corrosion. This investigation can be significant for understanding the metallurgical mechanisms and performance evolution of Mg-Li alloys during thermomechanical processes.

Optimization of Anodizing Condition for Mg-14mass%Li-3mass%Al Alloy

Mg-Li system alloys also has excellent cold-workability compared to commercial hcp-structured Mg alloys. However, Mg-Li alloys have poor corrosion resistance because not only that is Mg-based alloy but Li as a major alloying element is a less noble metal. For example, Mg-Li alloy sheet indicates high corrosion rate and exfoliation corrosion as a result of long-term corrosion test. The authors reported Mg-14 mass%Li-3 mass%Al alloy has the highest corrosion resistance in β-type solid solution alloy. Even though the optimized alloy composition, the alloy does not have enough corrosion resistance for practical use. In this study, anodized coating on Mg-Li alloy using phosphate solution was investigated. Anodizing of Mg-Li alloy facilitates the dissolution of substrate because of high Li concentration in this alloy. Therefore, the anodizing conditions were widely examined. As a result, the coating with approximately 15-20 μm of the surface layer was successfully formed. The surface layer was composed of MgAl2O4 and some phosphorus compounds. The thickness of anodized layer varied with the anodizing conditions. The dense surface layer was formed at a certain anodizing voltage and the corrosion resistance of anodized Mg-Li alloys was improved. However, the surface has some cracks and large flaky compounds. The formation mechanism of dense layer during anodizing were discussed.