Lithium Aluminum Research Articles

Effect of post-weld heat treatment on the microstructure, phase composition and mechanical properties of dissimilar Al-Mg-Li/Al-Cu-Li laser welded joints

Butt joints of the V-1461 and 1424 heat treated aluminum–lithium alloys of the third generation were welded with a CO2 laser and studied in detail for the first time. In particular, spatial distributions of the formed phases and their evolution upon post-weld heat treatment (PWHT), determining the mechanical properties of the joints, were investigated. The PWHT included quenching and subsequent artificial aging. The key factors, affecting the metallurgical processes in a weld pool, were the following: 1) the alloying elements and the thermal properties of the alloys, 2) the dynamics of the local non-equilibrium melting, the convective transfer of the molten metal in the weld pool and its subsequent solidification, 3) the cooling rate, and 4) the PWHT procedure. By using synchrotron radiation and scanning electron microscopy, new θ(Al2Cu), T1(Al2CuLi) and S1(Al2MgLi) phases were found in the weld metal that were absent in both base metals. This phenomenon reduced the mechanical properties of the joints to the levels, corresponding to about 50 % of the 1424 alloy as the weakest one. Quenching contributed to the formation of the δ′(Al3Li) strengthening phase in the weld metal. As a result, the ultimate tensile strength increased up to 70 % and elongation up to 95 % of the corresponding levels of the 1424 alloy. Artificial aging made it possible to form the T1(Al2CuLi) strengthening phase, to increase the content of the δ′(Al3Li) one, as well as to improve the mechanical properties of the joint. In this case, the ultimate tensile strength was 411 MPa, the yield point was 327 MPa and elongation was 1.7 %. These values were close to those for the 1424 alloy (about 80 %, 89 % and 23 %, respectively).

Effect of inhomogeneous microstructures on stress corrosion cracking sensitivity of 2050-T84 Al-Li alloy thick plate

Inhomogeneous microstructures in the thickness direction and stress corrosion cracking of 2050-T84 Al-Li alloy thick plate was investigated. The quarter layer of alloy thick plate exhibited the highest stress corrosion cracking sensitivity, which was related to AlCuMnFe IMPs, subgrains, orientation, T1 phase and dislocation density. In the quarter layer, the obstruction of subgrains to deformation bands resulted in significant stress concentration. Cracks originated from corrosion pits caused by AlCuMnFe IMPs around subgrains. The dealloying corrosion of T1 phase and the presence of Goss texture increased the brittleness of the alloy, further accelerating the stress corrosion cracking of the quarter layer.

Estimation of mode I quasi-static fracture of notched aluminum–lithium AW2099-T83 alloy using local approaches and machine learning

Aluminum–lithium (Al–Li) alloys offer superior performance under different conditions that involve mechanical loading, high temperature and corrosive environment. Therefore, Al–Li alloys are being used in the defense, aerospace, and aircraft industries, specifically in structural parts such as fuselage, empennage, and wings. By modifying the chemical composition, a third generation of Al–Li alloys has been introduced to overcome the mechanical and thermal shortcomings of previous Al–Li generations. As structural parts usually contain notches, it is of paramount importance to study the strength of the newly introduced alloys in the presence of such geometrical discontinuities to select the suitable alloy for a particular application. The aim of this work is to analyze the strength of U and V-notched specimens machined from extruded AW2099-T83 Al–Li alloys under quasi-static loading. The fracture stress of specimens with various notch radii and angles were estimated using strain energy density (SED) and the theory of critical distances (TCD) methods. A support vector machine (SVM) regression model was also implemented to assess the applicability of estimating fracture stress using machine learning approaches. The results show an average absolute discrepancy of 6.6 %, 7.8 % and 2.8 % for SED, TCD and SVM methods, respectively.

Microstructure evolution, mechanical response, and corrosion resistance for a 2195 Al-Li alloy under different rolling reductions during cryorolling

This study used cryorolling (CR) and room temperature rolling (RTR) with different rolling reductions to process the 2195 aluminum-lithium alloy (Al-Li alloy, AA2195) sheets. Subsequently, the AA2195 sheets were artificially aged to the peak aging stage. Their mechanical properties, corrosion resistance, and microstructural evolution sheets were investigated using methods such as hardness testing, tensile testing, intergranular corrosion (IGC) experiments, electrochemical experiments, transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). Compared to the RTR samples, the CR samples exhibited higher hardness, ultimate tensile strength, and elongation under the same rolling reduction conditions due to the combined effect of dislocation strengthening, grain boundary strengthening, and precipitation strengthening. The corrosion resistance of the RTR samples showed a declining trend with the increased rolling reduction. However, the corrosion potential of the CR samples exhibited a non-monotonic trend, first increasing and then decreasing, with the increased rolling reduction. The CR and RTR samples had similar microstructural evolution trends, leading to predominantly IGC morphologies in the IGC tests. The RTR and CR samples exhibited partial pitting morphologies at 70% rolling reduction, and the CR samples had more pronounced pitting characteristics than the RTR samples.

Photo-switchable Collectors for the Flotation of Lithium Aluminate for the Recycling of the Critical Raw Material Lithium.

Flotation of the mineral lithium aluminate by application of the natural product punicine from Punica granatum and some derivatives as collectors is examined. Punicines, 1-(2',5'-dihydroxyphenyl)-pyridinium compounds, are switchable molecules whose properties can be changed reversibly. They exist as cations, neutral mesomeric betaines, anions, and dianions depending on the pH. In light, they form radicals. Five punicine derivatives were prepared which possess β-methyl, β-chlorine, γ-tert.-butyl, and γ-acetyl groups attached to the pyridinium ring, and a pyrogallol derivative. On the other hand, LiAlO2 reacts with water to give species such as LiAl2(OH)7 on its surface. Flotations were performed applying the punicines in daylight (3000 lux), in darkness (<40 lux) and under UV-irradiation (4500 lux, 390-400 nm). The pH of the suspension, the collector's concentration, the conditioning time as well as the flotation time were varied. The recovery rates strongly depend on these parameters. For example, the recovery rate of lithium aluminate was increased by 116 % on changing the lighting condition from daylight to darkness, when the pyrogallol derivative of punicine was applied. UV, FTIR, TGA and zeta potential measurements as well as DFT calculations were performed in order to gain insight into the chemistry of punicines on the surface of LiAlO2 and LiAl2(OH)7 in water which influence the flotation's results.

Strain-dependent heterogeneity of microstructure and mechanical properties of 2195 Al–Li alloy during power spinning and heat treatment

The effect of thickness reduction (20 % in each pass) on microstructure evolution and mechanical properties of 2195 Al–Li alloy during hot power spinning and the subsequent heat treatment were investigated. As a result, high-performance 2195 Al–Li alloy tube with a thickness of 1.56 mm was successfully fabricated. The results showed that the strain localization of spinning led to the heterogeneity of microstructure and mechanical property along the wall thickness direction of the spun tube. With the increase of thickness reduction, dynamical recrystallization set up from the outer surface and propagated to the inner surface, and thus refined the microstructure, improved the mechanical properties, and reduced the heterogeneity in the microstructure and mechanical properties of the spun tube. However, after heat treatment, abnormal grain growth appeared in the microstructure near the inner surface of the spun tube with a moderate thickness reduction, triggering a severer inhomogeneity in the microstructure and mechanical properties. A large enough thickness reduction could induce sufficient dynamic recrystallization, which led to the disappearance of abnormal grain growth of spun tube during heat treatment. Grain boundary strengthening and precipitation strengthening were the dominant strengthening mechanisms of 2195 Al–Li alloy spun tube.

The precipitation and corrosion behaviour of cast Al–Mg–(0.7, 1.3) Li–Cu alloys

Achieving the development of ultra-light Al–Li alloys with high strength and excellent corrosion resistance is always a challenge. In this study, the precipitation characteristics and electrochemical corrosion behaviours after isothermal aging of cast Al–Li alloys with two different Li contents were comparatively analysed. The results showed that the increase in Li content from 0.7 wt-% to 1.3 wt-% retarded the peak hardening and improved the Al–Li alloy hardness and strength by promoting the precipitation of the S′ (Al2CuMg) and T1 (Al2CuLi) phases. Besides, the galvanic coupling corrosion of the alloying element Cu with the aluminium matrix was reduced by more Li addition, thus improving the corrosion resistance of the alloy.

Effect of impact-corrosion coupling damage on fatigue properties of 2198-T8 aluminum-lithium alloy

The peeling of aircraft surface paint due to foreign object impact can expose the aluminum–lithium alloy substrate to atmospheric corrosion, resulting in the fatigue performance being affected by the combined effect of impact damage and corrosion damage. In this work, the effects of impact damage and corrosion damage on the fatigue life of 2198-T8 aluminum–lithium alloy sheet were investigated. The strain field distribution of specimens with coupled impact and corrosion damage under cyclic loading was analyzed by Digital Image Correlation (DIC) technique, and the coupling relationship between impact and corrosion damage was analyzed based on the crack propagation path and fracture morphology. The results show that surface corrosion pits depth distribution of impact dents follows the same trend as residual stress distribution. For the coupling damage of the hemispherical punch, the coupled effect between impact damage and corrosion damage is most evident at low impact energy. At higher impact energies, the impact damage dominates the coupling damage. As the salt spray corrosion time increases, the fatigue life decrease rate gradually slows with increasing impact energy, and the impact damage has a greater effect on the fatigue life in the early corrosion stage. Compared to the salt spray corrosion environment at 35 °C, the fatigue life of the specimen at 25 °C increased by a maximum of 50.48 % as the impact energy increased from 10 J to 25 J.

The effect of pre-deformation on the mechanical properties of Al–Li–Cu + TiC/TiB2 alloy

In this study, Al–Li alloys containing TiC + TiB2 particles were successfully prepared by mechanical stirring method. The alloy organisation and nanoparticles were investigated by scanning electron microscopy (SEM) and electron probe microanalyser (EPMA). The number of T1 phases in the alloy matrix after different pre-deformation was investigated by transmission electron microscopy (TEM). The results showed that TiC and TiB2 acted as nucleation plasmas for grains during solidification, promoting non-uniform nucleation and refining the grains in the 0.5 samples, the main recrystallisation mechanism of the alloy during solidification was the particle-stimulated nucleation (PSN) mechanism, and the incorporation of nanoparticles improved the recrystallisation resistance of the alloy, while the yield strength of the alloy firstly increased and then decreased as the amount of pre-deformation increased, and the best tensile properties occurred The yield strength and tensile strength of 0.5 samples after 5% pre-deformation were 580 MPa and 603 MPa, respectively.

Research Progress of New Generation of Aluminum–Lithium Alloys Alloying

Aluminum–lithium alloy, being the lightest aluminum‐based alloy, holds significant potential for applications in the aerospace and military sectors. Currently, alloying treatment stands as a crucial method for enhancing the comprehensive performance of aluminum–lithium alloy. This article provides an overview of the production process of aluminum–lithium alloys, encompassing smelting and deformation processing characteristics. Additionally, it outlines the developmental history of the chemical composition for the primary grades of aluminum–lithium alloy, detailing the copper (Cu) and lithium (Li) content of the main alloying elements. And discusses the influence of various microalloying elements on the alloy's properties. Additionally, it summarizes the structure, properties, and precipitation morphology of the three primary strengthening phases formed by the alloying of aluminum–lithium alloys: T1 (), (), and (). The analysis also examines the impact of anisotropy on the mechanical properties of the primary dispersion. Finally, the article addresses the challenges involved in alloying aluminum–lithium alloys and proposes key research directions for element composition design.

Suppressing lithium dendrite via hybrid interface layers for high performance quasi-solid-state lithium metal batteries

The quasi-solid-state metal battery stands out as a promising candidate for the advancement of scalable, safe, and high-performance battery technologies. However, a major challenge remains in the form of short circuits arising from dendrite penetration, a consequence of uneven lithium deposition at the solid electrolyte/lithium anode interface. To address this issue, an in-situ constructed three-dimensional LiCl/Li-Al hybrid protective layer was implemented to inhibit the growth of dendrites. The enhanced interfacial dynamics were meticulously elucidated through a synergistic analysis of simulation and experimental results, highlighting the facilitation of Li+ flux distribution and uniform mass transfers introduced by the lithiophilic Li-Al alloy component. As a result, the modified Li anode enables stable Li stripping/plating cycling at a high current density of 1.0 mA·cm−2 and over 500 h at 0.2 mA·cm−2 for 0.2 mAh·cm−2 in the quasi-solid-state symmetric batteries. Additionally, the full cell with a LiFePO4 cathode maintains a high discharge capacity of 136.2 mAh/g after 400 cycles at 0.5C with a capacity retention of approximately 90 %. These findings demonstrate the application potential of Li anodes with a surface treatment for quasi-solid-state lithium metal battery applications.

Process parameters settings of friction stir welding using multi-response optimization for aluminum alloys

The defense and aerospace industries utilize the AA2050, an aluminum-lithium alloy of the third generation. Principal component analysis (PCA) and Taguchi-grey relational analysis (GRA) are utilized in this study to enhance the process constraints for friction stir welding (FSW). The quality of the weld can be influenced by various process factors such as the speed at which the weld is traversed, the speed at which the tool is rotated, the angle at which the tool is tilted, the diameter of the shoulder, and the shape of the tool pin. The combination of PCA and the well-known Taguchi-GRA approach enables the objective estimation of response weights. Here, a Taguchi L16 orthogonal array was designed, and sixteen tests were carried out using it. These experiments were conducted with various assessments including tensile strength, yield strength, elongation percentage, hardness of the weld zone, bending load, etc Through the utilization of Taguchi-GRA-PCA analysis, the most suitable process parameters were identified as a traverse speed (TS) of 160 mm min−1, a rotating speed (RS) of 900 rpm, a tilt angle (TA) of 2 degrees, a shoulder diameter (SD) of 16 mm, and with a straight square tool pin profile (TPP). ANOVA revealed the relevance of all five characteristics, with rotational speed being the most influential, accounting for 43.56% of the entire result. A confirmation experiment done under ideal conditions revealed a significant improvement in total weld quality of 19.06%.

Characteristics and properties of anode materials for lithium-ion batteries

Lithium-ion secondary batteries (LIBs) are battery systems with high energy densities. They are essential components of todays information-rich, mobile societys portable, entertainment, computing, and telecommunications technology. After 1981, most of the research on anode materials mainly focused on the anode containing Li, such as LiAl alloy, LiC alloy, etc. These materials have high prices, unstable cycling performance, and are difficult to be commercialized. The successful commercialization of LIBs began in 1991 with SONYs manufacturing of petroleum coke-based anode materials. Among them, anode plays a crucial role in LIBs. Anode materials that have been commercialized include carbon, alloys, and lithium titanate. Lithium-ion batteries using carbon anode materials and lithium titanate anode materials can meet the needs of electric vehicles (EVs) and large-scale energy storage applications to a certain extent, and alloy anode materials can promote the energy density of LIBs. The properties of the commercialized anode materials are covered in this paper. Next generation anode materials such as silicon anode materials are also introduced.

Unveiling the origin of severe hot cracking susceptibility in Al-Li alloys

This work reports a new mechanism for the severe hot cracking susceptibility (HCS) of cast Al-Li alloys. In contrast to the narrow vulnerable solidification temperature range increasing cracking resistance, alloys with high Li content or solute content, which are supposed to show lower HCS, instead exhibit anomalously high HCS. Results reveal that this phenomenon arises from a variety of Li-rich inclusions distributed in the interdendritic paths, including Li2O, LiAlO2, Li2CO3 and LiH. These particles can form spontaneously with O2, CO2 and H2O during solidification, deteriorating the interfacial bonding capacity. Meanwhile, the occupation of refilling channels for residual liquid increases the potential risk of microcrack initiation. These unfavorable factors promote the rapid propagation of cracks from the casting surface inward, which eventually leads to catastrophic fractures.

Insights for the strength and ductility of precipitation hardening Al–Li–Sc alloys

Al–Li alloys with high elastic modulus, low density and high specific strength have been widely used in aerospace industry. However, although Al3Li precipitates enhance the strength significantly, the appearance of shearable Al3Li precipitates usually decreases the ductility, leading to the strength-ductility trade-off. In this study, the strategy of microalloying is applied to fabricate an Al–2.46 Li–0.2 Sc (wt.%) alloy with tunable precipitate sizes by heat treatment. This alloy exhibits a good combination of strength and ductility when the precipitate radius is smaller than 6.7 nm or larger than 16.4 nm. The strengthening mechanisms in Al–Li–Sc alloy with different precipitate sizes are quantitatively discussed. With the increase of precipitate size, the dominant precipitation strengthening mechanism changes. The influence of precipitate on ductility is mainly achieved by influencing the dynamic recovery rate of dislocation which can be illustrated by a dislocation-based model. When the precipitate size is relatively small or large, the Al–Li–Sc alloy exhibits a higher ductility owing to a lower dynamic recovery rate. This study provides insight for understanding the strength and ductility in Al–Li–Sc alloy as well as potential theoretical guideline for designing novel high-performance Al–Li based alloys.

A novel high-strength Al–Li alloy printed by laser powder bed fusion: Microstructural evolution and strengthenin mechanism

This paper obtained an additively manufactured high-strength Al–Li alloy by laser powder bed fusion (LPBF) based on a third generation AA2195 alloy powder raw material. The relationship between the process optimization, microstructure evolution, and mechanical properties of the as-printed (AP) and heat-treated (HT) specimens was established for the first time to explain the intergranular fracture sensibility during LPBF and reveal the dominant precipitation strengthening mechanism induced by the subsequent heat treatment. The precipitation order of AP Al–Li alloy at the last stage of the solidification process was: L (Liquid phase) →T2 (Al6CuLi3) + θ′(Al2Cu) + δ′/β' (Al3(Li,Zr)) + T (LiAlSi) + Ω (AlCuMgAg). The micro-cracks caused by a relatively high grain boundary coverage of interconnected film-like eutectic phases, as well as micro-voids caused by the localized slip between the coarse T2-phases and soft precipitate-free zones, resulted in the high intergranular fracture sensibility. The well-designed T6 heat treatment of 515 °C/60 min solution treatment and 170 °C/6 h aging treatment was conducted to maximize the precipitation strengthening by T1-phases. The precipitation order of HT Al–Li alloy was supersaturated solid solution → GP zone + δ′/β' → θ′ + T1 (Al2CuLi) + ω (Al7Cu2Fe) + β′. The presence of continuously distributed T1-cells along the grain boundaries was not only capable of providing a pinning effect on dislocations movement and boundary migration, but also able to shorten the pile-up distance on the slip plane. Such phenomena improved the resistance ability of Al–Li alloys to mechanical damage and permitted a significant strength enhancement.

Microstructure and mechanical properties of Sc/Zr modified 1460 Al–Li alloy fabricated by laser powder bed fusion

The preparation of Al–Li alloy by laser powder bed fusion (LPBF) technology, especially Al–Li alloy with high Li content, is of great significance for lightweight of aerospace equipment. However, the significant susceptibility of Al–Li alloys to hot cracking during the process limits their advancement. This study starts from the two aspects of process control and composition modification, to achieve the production of crack-free and high-quality 1460 Al–Li alloys. Crack-free 1460 specimens can only be prepared at extremely low scanning velocity. The process window is markedly expanded by Sc/Zr modification. The heterogeneous nucleation of Al3(Li,Sc,Zr) results in significant grain refinement and effectively suppresses crack initiation and propagation. The unique bimodal heterogeneous microstructure endows the alloy with notable mechanical properties. After the addition of 0.6Sc-0.3Zr, the ultimate tensile strength (UTS), yield strength (YS), and elongation (δ) of 1460 alloy are increased by 104 %, 158 %, and 43.9 %, respectively. The strength-plasticity synergism is primarily attributed to grain refinement strengthening, precipitation strengthening, and hetero-deformation induced strain hardening resulting from its unique bimodal heterogeneous microstructure. The UTS and YS of 1.2Sc-0.6Zr modified 1460 alloy increased by 156 % and 279 %, respectively. However, this further increase in the Sc/Zr content significantly deteriorates the plasticity of the alloy. This work establishes a foundation for advancing the use of Al–Li alloys in high-performance, lightweight, and complex aerospace structures.

Effect of pre-rolling and aging temperature on the microstructure and mechanical properties of creep-aged 2050 Al–Li alloy

The influences of aging temperatures (160–200 °C) and 8% pre-rolling on the mechanical properties, and microstructures of the creep-aged AA2050 alloys were investigated. The results show that for the solid-solutioned alloys after the creep aging, the strength increased with an increase of aging temperatures. The ultimate tensile strength (UTS) and yield strength (YS) reached the highest value of 527 and 484 MPa at 200 °C, respectively, although the elongation (EL) reduced to 10.8%. At expense of σ phases, the temperature increase promoted the dislocation accumulation and the dense precipitation of θ′ and T1 phases, which increased the strength. It is noted that the strong oriented precipitation at 200 °C lost some strengthening effect. After the 8% pre-rolling, the strength of creep-aged alloys increased firstly and then decreased with the increase of temperature. The high strength (UTS = 574 MPa, YS = 535 MPa) at 180 °C was attributed to the dense precipitation of T1 phases under the action of diffusion kinetic and thermodynamic driving force. When the temperature reached 200 °C, the activated ledge mechanism significantly thickened T1 phases, thus decreasing the strength. The work revealed the critical roles of aging temperature and pre-rolling in tailoring precipitation behaviors and mechanical performance of Al–Li alloys, paving a way in designing creep-aged Al–Li alloys with the superb mechanical properties.

Formability of 2195-T4 Al–Li alloy sheet by electromagnetic forming

This study explored the efficacy of electromagnetic forming in addressing the limited formability of aluminum–Lithium (AlLi) alloy at room temperature, focusing on the AA2195-T4 sheet. Comparative analyses were conducted to assess the formability. The results indicated that the limit strains obtained through electromagnetic forming were at least 50%, 10%, and 50% higher compared with those obtained through rigid punch forming under the uniaxial tension, plane strain, and biaxial tension. Upon utilizing forming limit diagrams, the failure processes during electromagnetic flanging were predicted. Notably, electromagnetic flanging enabled the creation of hole-flanging structures with a 60% increase in the flanging limit strain around the circumference, surpassing the capabilities of rigid punch flanging. Moreover, the maximum time window for electromagnetic flanging was extended to 168 h. Analysis of the flanging strain path indicated that cracks were prone to occur near round corners during electromagnetic flanging, contrasting with rigid punch flanging where cracks tended to form near the edges of straight walls. This study offered valuable insights for aerospace component formation utilizing Al–Li alloys at room temperature.

A Review on Distribution of Reinforcement and tensile Strength of Aluminum Lithium Alloy based Nano Metal Matrix Composites Fabricated by STIR Casting

Aluminum Alloy (AA) parts are employed in lightweight engineering fields and have poor mechanical, wear, and corrosion resistance. Aluminum Matrix Composites (AMCs) are materials created by incorporating hard reinforcing particles into an aluminum matrix alloy. The new material has improved characteristics, including higher specific stiffness and strength, as well as higher corrosion resistance, elastic modulus, wear resistance, and low weight. Metal Matrix Composites (MMCs) are composite materials in which metal serves as the matrix and hard particles or ceramics serve as reinforcement. MMCs are used to improve the functionality of a wide range of technical materials. It could be used in many different fields, including aerospace, automotive, space travel, and medicine. In this paper, the reviewer investigates the distribution of reinforcement and Tensile Strength (TS) of Aluminum Lithium (Al-Li) Alloy/Nano Al2O3 MMC fabricated by stir casting. Finally, the authors provide a comparative analysis of prior reviewed research papers. After comparative analysis, TiB2/2195 composite has higher Tensile Strength (115.4%) than the other composite such as AA7010-TiB2 (260%), Al2O3 + SiC (72%), A356/SiC (21.87%), and Al-SiC (37%).