Lithium Aluminum Research Articles

Influence of post-weld rolling and artificial aging on microstructure and mechanical properties of friction stir welded 2195-T4 Al-Li alloy joints

Fiction stir welding (FSW) of a naturally aged (T4) 2195 Al-Li alloy was conducted to study the effect of post-weld artificial aging (AA) and rolling+artificial aging (R+AA) on microstructure and mechanical properties of the FSW joints. Grain features were analyzed by electron back scattered diffraction (EBSD) technology, and precipitates were characterized using transmission electron microscopy (TEM) along [011]Al and [001]Al zone axes. Mechanical properties of the joints were evaluated through micro-hardness and tensile testing. The results indicate that grain development, including grain orientation, grain boundary components and dislocation density, varies within different regions of the As-welded joints due to complicated thermal-mechanical history. The alloying elements mostly exist as Guinier-Preston zones in the base material (BM) with a few formations of δ'/β', and slightly precipitate into T1 in the heat affected zone (HAZ), form σ in the thermal-mechanical affected zone (TMAZ), as well as develop T1 and S' in the nugget zone (NZ) after FSW. The lowest hardness zone (LHZ) exhibits elevated precipitation levels, generating coarse T1 and grain boundary precipitates with evident σ and precipitate free zone. The overall precipitation level of the As-welded joints remains minor, resulting in a slight decrease in hardness at the LHZ. Post-weld AA promotes many T1 formations, enhancing the joint strength and hardness. As a result, the ultimate tensile strength (UTS) of the joints increases from 440 MPa to 506.5 MPa, while the elongation decreases from 13.5% to 3.4%. Furthermore, hardness profiles transform from a low-amplitude wave curve to a high-amplitude W-shaped curve, generating a significant LHZ due to the minimal precipitation of T1. Pre-rolling deformation can enhance dislocation density and low angle grain boundaries (LAGBs), promoting the nucleation of high-density, fine T1 during artificial aging, and especially improves precipitation ability of the LHZ, leading to an elevated hardness increment in the region after AA. Compared to the Joint-AA, both strength and elongation of the Joint-R+AA increase, obtaining 530.5 MPa and 3.9%, respectively.

Effect of Rolling and Artificial Aging Treatment on the Microstructure and Mechanical Properties of a 2195 Al–Li Alloy by Ultrasonic Casting

Effect of Rolling and Artificial Aging Treatment on the Microstructure and Mechanical Properties of a 2195 Al–Li Alloy by Ultrasonic Casting

Crack analysis in laser powder bed fusion-fabricated 2195 Al-Li alloy: An in-depth examination of influential variables

Laser powder bed fusion (LPBF) of high-strength 2195 Al-Li alloys offers significant industrial potential, yet the process is hindered by a high susceptibility to hot cracking. This study systematically investigates the hot cracking mechanisms and the key processing parameters influencing crack formation in LPBF-fabricated 2195 Al-Li alloys. Extensive experimental analysis revealed that crack density is significantly affected by scanning velocity and laser power, with scanning velocity identified as the most critical factor through a neural network model and a crack susceptibility model. The study demonstrates that achieving crack-free samples requires extremely low scanning velocities, as higher velocities exacerbate crack formation, particularly at high-angle grain boundaries (HAGBs). The findings also highlight the limitations of preheating in reducing crack susceptibility, emphasizing the importance of precise control over processing parameters to mitigate cracking in LPBF-fabricated 2195 Al-Li alloys.

Effect of ultrasonic surface rolling on the microstructure and mechanical properties of 2195 Al-Li alloy fabricated by laser powder bed fusion in various build directions

To address the challenges of poor forming quality in the laser additive manufacturing of lightweight alloys, this paper explores an approach that integrates a laser additive manufacturing strategy for lightweight alloys with surface deformation strengthening. The study investigates the combined effects of build direction (BD) and ultrasonic surface rolling (USR) on the microstructure, residual stress, and mechanical properties of 2195 Al-Li alloy processed by laser powder bed fusion (LPBF). The results indicate that changes in BD significantly affect the growth direction of columnar grains (CGs) in the formed specimens and lead to the formation of a gradient microstructure with different characteristics under the influence of USR. When BD is 0°, the post-USR specimen exhibits the most significant deformation strengthening effect, with the high dislocation density reaching depths of up to 720 μm and compressive residual stress amplitudes up to −159 MPa. When BD is 90°, the sample shows excellent tensile performance with an ultimate tensile strength (UTS) of 386 MPa and an elongation (EL) of 8.2 %. After USR treatment, the UTS of the sample increases to 438 MPa, but the EL decreases to 5.1 %. CGs exhibit varying deformation resistances in different directions, thereby influencing the deformation strengthening effect of USR and altering the crack propagation mechanism during the tensile process.

Effect of pulse current on the creep ageing behavior of pre-strained 2195 Al-Li alloy

Pre-strained aluminum lithium (Al-Li) alloy plates have ultra-high strength and comprehensive performance after aging treatments, and are widely used in the aerospace industry. The initial increase in dislocation density caused by these pre-strains will significantly affect the evolution of deformation, microstructure, and mechanical properties during the pulse current assisted creep ageing forming process. Therefore, the effect of pulse current on the creep ageing behavior of 2195 Al-Li alloy with different pre-strains (0%, 4%, and 8%) was investigated. As the pulse current increases within the first 1h creep aging process of the various pre-strain samples, the 1h creep strain significantly increases and the subsequent steady-state creep rate slightly reduce. Moreover, the larger the pre-strain, the higher the total creep strain. Pulse current promotes the movement and recovery of initial dislocations, and promotes the fine formation of T1 phase and suppresses the nucleation of θ' and phase, thereby improving mechanical properties. Compared with the conventional creep ageing process, the pulse current acting on pre-strained 2195 Al-Li alloy significantly increased the peak aged strengthen and shorten the peak aging time. Meanwhile, the peak time platform period has also been significantly extended. It is evident that the application of pulse current assisted creep ageing forming process to pre-strained 2195 Al-Li alloy plates can significantly improve formability and mechanical properties, enlarges the forming process window and realize collaborative manufacturing of Al-Li alloy component shape and performance.

Effect of bath temperature on corrosion resistance of electroless Ni-P coating on 5A90 Al-Li alloy

Abstract The Al-Li alloy exhibits outstanding characteristics, including remarkable specific strength, elevated specific stiffness, and heightened susceptibility to localized corrosion. Electroless Ni-P coating is extensively applied over the appearance of aluminum alloys to enhance their corrosion resistance. Electroless Ni-P coating was applied to 5A90 Al-Li alloy at various plating temperatures for the study presented in this publication. The coating’s surface, composition, and cross-sectional morphology were examined using SEM/EDS. The corrosion behavior of coating was studied using the potentiodynamic polarization curve. Results showed that coating on the surface of 5A90 Al-Li alloy was uniform and smooth. Ni and P elements were evenly distributed in the coating. The thickness of coatings at 80°C, 85°C, 90°C and 95°C was about 3.98 μm, 5.5 μm, 11.2 μm, and 10.29 μm, respectively. As the temperature of the bath increased, the corrosion resistance of the coating first increased and afterward decreased. The corrosion resistance of the coating might be correlated with its thickness.

Precipitation behavior of Al2CuLi, Al3Li and Al3Zr in A2060 aluminum-lithium alloys and mechanical behavior of their microinterfaces

The precipitated phase of Al-Li alloy is a major factor determining the properties of Al-Li alloy. Al2CuLi phase(T1 phase), Al3Li phase and Al3Zr phase are all important enhanced precipitated phases. In this paper, the properties of the matrix, the precipitated phase and the interface formed between each phase are calculated. The (111) crystal face of Al, (111) of Al3Li, (111) of Al3Zr, and (210) of Al2CuLi are the surfaces with the lowest surface energy of these phases. Al3Li/Al3Zr has the lowest interfacial energy (0.01961ev), so its thermodynamic stability is the best. The interface with the maximum bonding strength is the interface of Al3Zr/T1, and its adhesion work is 0.61878ev. A2060 aluminum-lithium alloy was thermally insulated at 580 °C for 2h and then hot rolled. After hot rolling, it was cooled to room temperature for cold rolling. Then the samples were treated with solid solution and aging, and different cooling methods were selected to obtain four kinds of samples: non-heat treatment, aging, air cooling and water quenching. It is found that the strength and hardness of Al-Li alloy are determined by the grain thickness of precipitated phase, and the ductility and hardness of Al-Li alloy are determined by the number of precipitated phase and the degree of dislocation density.

Role of alloying and heat treatment on microstructure and mechanical properties of cast Al-Li alloys: A review

Role of alloying and heat treatment on microstructure and mechanical properties of cast Al-Li alloys: A review

Laser additive manufacturing of Ti and Ce co-modified 2195 difficult-to-process aluminum alloy: Grain refinement, cracking suppression and enhanced mechanical properties

High cracking susceptibility of Al-Li alloys with Ti/CeB6 addition is thoroughly suppressed in laser powder bed fusion (LPBF) processing of Ti/Ce co-modified 2195 alloys at relatively high scan speeds, while the cracking suppression mechanism and phase formation in these composites are not clarified. In this work, microstructure evolution and mechanical performance of the LPBF-fabricated Ti/Ce co-modified 2195 are investigated to reveal their cracking suppression and strengthening mechanisms. The results show that apparent grain refinement of the composites is ascribed to high supercooling from rapid formation of constitutional supercooling zone in front of solid–liquid interfaces by high-Q-value Ti solute, and heterogeneous nucleation of in situ formed Al3Ti and Al11Ce3 precipitates. Their synergistic interactions promote formation of fine equiaxed grains and thus inhibit crack initiation. The composites exhibit high microhardness of 100 ± 5 HV0.2, nano-hardness of 1.6 ± 0.1 GPa and elastic modulus of 97 ± 3 GPa, where the elastic modulus increases by ∼27% and ∼31% compared to those of LPBF-processed and conventionally manufactured 2195 alloys, respectively. A tensile strength of ∼336 MPa and an elongation of ∼3% are obtained from in-situ synchrotron X-ray diffraction measurement. The improved properties are derived from grain refinement and Orowan strengthening. Based on the optimal processing parameter and composition, a bracket component filled with lattice structures is designed and manufactured with good manufacturing quality and processing accuracy.

Influence of friction stir welding on the localised corrosion behaviour of AA2060 T8E30 and AA2099 T83 Al-Li alloys

The effect of friction stir welding (FSW) on the microstructure and localised corrosion behaviour of the dissimilar weld of AA2099 T83 and AA2060 T8E30 alloys is investigated. FSW results in a drastic change in the microstructure thus altering their corrosion behaviour. The heat-affected region exhibits similar attack morphology to their respective base metal but is the most protected region. The stir zone (SZ) is the most susceptible to attack. During immersion of the entire weld, attack initiation occurs from the AA2060 SZ due to galvanic activity within the region caused by the overlap of the grains in the weld zone.

In-situ study on the effect of Li concentration on hydrogen microporosity evolution in Al-Li alloys by synchrotron X-ray radiography

The nucleation and growth of hydrogen microporosity during the solidification of Al-Li alloys were in situ observed by synchrotron radiation X-ray radiography, and the effect of initial Li concentration on its evolution kinetics was investigated. The results show that the high Li concentration effectively contributes to the high-temperature nucleation effect of hydrogen microporosity during the solidification of Al-Li alloys, and significantly increases the nucleation and growth rates of hydrogen microporosity. When the initial Li concentration was 2.0 wt%, the nucleation supersaturation of hydrogen microporosity was 1.96, which was 3.5 times higher than that at low Li concentration (1.5 wt%), and the growth rate was up to 2.61 μm/s. In addition, the quantitative results of the final size, morphology, and distribution of the hydrogen microporosity based on 3D X-ray computed tomography (X-CT) showed that high Li concentration not only increased the volume of monolithic hydrogen microporosity, and increased the total number of microporosities, but also increased the degree of irregularity of hydrogen microporosity. The in-situ observation results can provide a new dataset for the establishment and validation of the hydrogen microporosity model of Al-Li alloys.

Microstructural Evolution, Precipitation Behavior, and Mechanical Property Response of Cast Al–Li–Cu–Cd–Mn–Zr–Ti Alloy

The microstructural evolution and mechanical properties of cast Al–Li–Cu–Cd–Mn–Zr–Ti alloy during heat treatment are investigated systematically. In these findings, it is shown that the as‐cast alloy exhibits fine and equiaxed grains. During the solid solution treatment, Al20Cu2Mn3 dispersoids effectively restrict grain growth, and reducing the solid solution time has a similar effect. Subsequently, the precipitation behavior and its effect on the mechanical properties during the aging process are revealed. Al3(Ti, Zr) particles are uniformly distributed throughout the matrix, acting as nucleation sites for δ′, θ′, and T1 precipitates. Overtime, δ′ precipitates gradually coarsen and decrease in number, and some δ′ precipitates attach to Al3(Ti, Zr) particles, forming core–shell Al3(Li, Ti, Zr) phases. At the same time, plate‐shaped θ′ and T1 precipitates emerge and coarsen. After aging at 160 °C for 24 h, the alloy exhibits an excellent combination of strength (yield strength =293.3 ± 4 MPa, ultimate tensile strength =468.0 ± 3 MPa) and ductility (elongation =9.6 ± 0.4%), surpassing those reported in other cast Al–3Li–2Cu–X alloys. Critically, the underlying mechanisms behind the microstructure and mechanical properties are discussed extensively, providing valuable insights for the advancement of cast Al–Li alloys.

Thermodynamic re-assessment of the Al-Li-Zn system

Aluminum-lithium alloys are a kind of highly promising material due to low density, high strength and excellent modulus properties. The proper addition of Zn can effectively promote the precipitation of the main metastable strengthening phase δ′(Al3Li). As a crucial sub-system of Al-Li alloys, literature data on phase diagram and thermodynamic properties of the Al-Li-Zn system as well as the Al-Li and Li-Zn binary systems were comprehensively evaluated by the CALPHAD approach. The Li-Zn system was reassessed mainly by considering the newly reported data on formation enthalpy and activity and a 2-sublattice (SL) model was applied to describe the βLiZn4 phase. The Al-Li system was modified by considering AlLi2 and describing the metastable phase δ′(Al3Li) with interconvertible 4SL and 2SL ordered-disordered models. The predicted metastable fcc solvus was in perfect agreement with the measurements. Considering the available experimental data, the ternary Al-Li-Zn system was then re-optimized and a self-consistent thermodynamic description of the ternary Al-Li-Zn system was presented. The predicted metastable two-phase region of (Al)+δ’(Al3Li) in Al-Li-Zn system can be coupled with the accessible experimental data, which can be expected to well assist in designing high-strength Al-Li alloys.

Microstructural evolution and dynamic mechanical behavior of PM 2195 Al-Li alloy with resistance to shear instability in high strain rate deformation

The risk of adiabatic shear instability is common in traditional alloys covering high-strength steels, copper alloys and aluminum alloys during high strain rate deformation. However, the research on shear instability of 2195 Al-Li alloy prepared by powder metallurgy (PM) at high strain rates is still blank. The purpose is to explore its microstructure evolution and dynamic compression behavior. In this work, the 2195 Al-Li alloy prepared by PM amazingly demonstrates excellent resistance to shear instability at high strain rates during Split-Hopkinson pressure bar (SHPB) experiment. The microstructural evolution of grains and T1 (Al2CuLi) precipitate phase, and dynamic compression behavior of PM 2195 Al-Li alloy at various strain rates from 3000 s−1 to 9000 s−1 are investigated in detail employing correlative electron-backscatter diffraction (EBSD) and transmission electron microscopy (TEM). During high strain rate deformation, the alloy undergoes grain fragmentation and rotation, increasing dislocation density around the grains. When the strain rate is from 3000 s−1 to 7500 s−1, the Kernel Average Misorientation (KAM) value increases, indicating intensified localized strain. At a strain rate of 9000 s−1, a small number of grains are surrounded by nanocrystals (around 200 nm) that undergo stress release, while the average size of micrometer-sized grains is 0.81 μm. As the strain rate increases, the T1 phases in the alloy extends, vibrates, and fractures before dissolving in the matrix, while high-rate deformation promotes dislocation entanglement and defects, leading to the decomposition or ordering of precipitated phases through rapid plastic deformation. By virtue of energy dissipation strategy via the formation of nanocrystallines and dislocation behavior induced by the dissolution of T1 phases, the "positive-positive" effect is observed. The PM 2195 Al-Li alloy undergoes no shear failure even at the strain rate of 9000 s−1, showing great prospects in future applications in dynamic-loading conditions.

Study on the effect of rare earth elements La, Ce, Y and Sc doping on the mechanical properties of aluminum–lithium alloys

In this paper, the effects of rare earth elements La, Ce, Sc, and Y on the bond strength of the aluminum–lithium alloy δ’ (Al3Li)/Al interface are investigated using first-principles calculations. The results show that the interfacial energy decreases after substitutional doping of Al atoms on both sides of the interface by rare earth elements, respectively, with values ranging from −2.0664 eV/Å2 to −1.9720 eV/Å2. The interfacial energy decreased by 2.0841 eV/Å2 and 2.0709 eV/Å2 when Ce and Sc elements replaced Al in the matrix, respectively. Uniaxial interfacial tensile simulations of Al/ Al3Li showed that the strain elongation of the material increased from 24 % to 42 % for the pure interface after doping with Sc elements at the interface. The same tensile tests yielded a maximum elongation at break of 3.25 % for Al-Li alloy after artificial aging at 0.6 % Sc content. Observation of the microstructure of the materials before and after rare earth doping using TEM reveals that the content of nanoscale Al3(Sc, Li) composite particles increases with the increase of Sc content after artificial aging at 185 °C for 10 h. Moreover, the presence of Al3Sc refines the precipitated phase of the alloy and improves the plastic toughness of the material.

Compositional Engineering of Lithium Metal Anode for High-Performance Garnet-Type Solid-State Lithium Battery.

Garnet-type solid-state lithium batteries (SSLBs) possess excellent potential owing to their safety and high energy density. However, fundamental barriers are deficient cycling stability and poor rate capability. The main concern lies in generating voids at the Li|garnet interface during Li stripping, stemming from the sluggish diffusion of Li atoms inside the bulk Li metal. Herein, a composite anode (AN@Li) containing Li-Al alloy, Li3N, and LiNO2 is designed by introducing aluminum nitrate into molten Li. The lower interfacial formation energies exhibited by Li-Al alloy, Li3N, and LiNO2 with garnet solid-state electrolyte (SSE) enhance the wettability of AN@Li toward SSE. Meanwhile, it affords efficient conductive pathways that facilitate Li+ diffusion in the bulk anode (not just on the surface). Impressively, the resulting symmetric cell with AN@Li electrodes achieves high critical current density (1.95mA cm-2) and long cycle life (6000h at 0.3mA cm-2). The SSLB coupled with LiFePO4 cathode and AN@Li anode enables stable cycling for 200 cycles at a high rate of 1 C with a retention of 96% and exhibiting outstanding rate capability (145.9 mAh g-1 at 2 C). This work provides practical insights for producing high-performance lithium metal anode for advanced garnet-type SSLBs.

Investigation of Al-Li particle ignition dynamics with different Li content

Promoting the ignition of aluminum powder is considered an effective method to inhibit the agglomeration of aluminum powder in propellants and enhance combustion efficiency. This study utilizes laser ignition technology and high-speed photography to investigate the ignition and combustion processes of single aluminum particles and aluminum-lithium alloy particles. The focus is on comparing the effects of the diameter of micron-sized metal particles and the lithium content in aluminum-lithium alloy particles on the ignition and combustion processes of metal particles. The results show that the ignition delay time is directly proportional to the diameter of the metal particles and inversely proportional to the lithium content. For the aluminum-lithium alloy particle with a lithium content of 3.5 %, even if the diameter is close to 300 μm, the ignition delay time is only 125.5 ms, which is much smaller than that of the pure aluminum particle with a diameter of 208 μm. Compared to aluminum particles and aluminum-lithium alloy particles, there is basically no difference between the two during the combustion stage. However, in the ignition stage, aluminum-lithium alloy particles sequentially exhibit a red gas-phase flame corresponding to lithium and a yellow gas-phase flame corresponding to aluminum. This indicates that during the ignition process of aluminum-lithium alloy particles, lithium first reacts with the oxidative atmosphere and releases heat, providing a heat source for the subsequent ignition of aluminum particles. This also explains why the ignition delay time of metal particles is inversely proportional to the lithium content. An ignition model for aluminum particles in a multi-component atmosphere is established, which further considers the chemical reactions between lithium and oxidative gases, making the model applicable to aluminum-lithium alloy particles. This ignition model effectively describes the impact of particle diameter and lithium content on the ignition process of metal particles. The model is further verified, and the results show that the calculated ignition delay is in good agreement with the experimental data. Overall, this study provides deeper experimental and theoretical insights into the ignition and combustion processes of aluminum-lithium alloys, and the findings can guide the application of aluminum-lithium alloys in propellants.

Microstructure and mechanical properties of 2195 Al-Li alloy via friction stir additive manufacturing with different stirring paths

Friction stir additive manufacturing (FSAM) is increasingly becoming a feasible method for aluminum alloy structure due to the unique forming characteristics. In this study, two different stirring paths were explored for 2195 Al-Li alloy and the microstructure evolution and mechanical properties were ‌investigated. An ultrafine grained microstructure was formed in the FSAMed zone with an average grain size ranging from 1 to 5μm. The microstructure in the FSAMed zone at the bottom exhibited a consistent direction trend and a significant increase in dislocation density. Different stirring paths had minimal impact on the phase distribution. Frictional heating led to the re-dissolution and re-precipitation of precipitates, resulting in T1, θ', and δ'/β' were distributed within the grains. The samples of intersecting stirring path showed similar mechanical properties in different directions, while the UTS of LD was 52.56 MPa higher than TD of the reciprocating path samples. The microhardness range for the intersecting stirring path ranged from 87.0 HV0.2 to 126.6 HV0.2, while the reciprocating stirring path exhibited a microhardness range of 83.8 HV0.2 to 132.4 HV0.2. In summary, this study provides valuable insights into designing processing paths for FSAM of 2195 Al-Li alloy.

Effect of temperature on creep aging behavior of the nugget zone of AA2195 Al[sbnd]Li alloy produced by friction stir welding

This paper aims to study the effect of temperatures on the creep aging behaviors of the nugget zone (NZ) of AlLi alloy by friction stir welding (FSW). The results suggest that the creep strain of the NZ experiences a significant increase as the temperature rises, surpassing that of the base material (BM) at equivalent temperatures. In the case of NZ, the elevation of temperature from 160 to 190 °C induces a pronounced increase in both the size and volume fraction of the T1 phase, which results in a substantial enhancement in the strength. In contrast, the peak-aged strengths of the BM exhibit minimal variation in this temperature range. As the temperature increases, the time required for the BM to reach its peak aging state significantly decreases, whereas the changes in the NZ are less pronounced. For the NZ, the time required to reach the peak aging state is obviously longer than that for the BM. Although the average length of the T1 phase in the NZ is markedly greater than that in the BM, its volume fraction and number density in the NZ are considerably lower than those in the BM, resulting in inferior strength reinforcement in the NZ compared to the BM after creep aging.

Efficient and Controllable Preparation of Super-Hydrophobic Alumina-Based Ceramics Coating on Aviation Al-Li Alloy Surface for Corrosion Resistance and Anti-Icing Behavior

Al-Li alloys have been widely applied in aircraft structural component and shell material. However, Al-Li alloys are prone to corrosion failure, which leads to a considerable safety risk in the aerospace field and greatly limits their industrial application. Herein, a simple, low-cost, and large-scale air-spraying technique is developed for the preparation of an alumina-based ceramics coating with enhanced corrosion resistance and anti-icing behavior. The results show that the static contact angle of the as-prepared coating is 157.2 ± 0.4°, and the rolling angle is only 9.8°, suggesting a super-hydrophobic surface. Meanwhile, the electrochemical corrosion potential of the coating is 70 mV higher than that of the substrate, and the corrosion current density of the coating also decreases by 1 order of magnitude, indicating a significantly improved corrosion resistance. In addition, the fabricated super-hydrophobic coating also shows excellent anti-pollution and anti-icing characteristics. This work provides positive guidance for expanding the application of hydrophobic coating in the aerospace industry, especially in some complex corrosion, icing, and pollution environments.