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The impact of erbium (Er) on grain refinement in Al–Cu–Li alloys is limited by the thermodynamic instability of Al3Er inoculants. Nevertheless, the concurrent addition of both Er and Zr to Al–Cu–Li alloys results in a marked refinement of the average grain size. Er exerts a significant influence on the precipitation sequence within Al–Cu–Li alloys, promoting a complete transition from δ′ (Al3Li) and θ′ (Al2Cu) to T1 (Al2CuLi) precipitates during aging at 120 °C, thereby substantially enhancing both strength and ductility. Through high-resolution transmission electron microscopy (HRTEM), the underlying mechanism of the T1 nucleation by Er microalloying has been elucidated. It has been demonstrated that the presence of Er leads to the formation of solute enrichment regions (SERs) comprising Cu, Zn, Mg and Er. These SERs serve as catalysts for the development of Cu-rich atomic planes along the {111}Al, providing a direct precursor structure for T1 nucleation. Consequently, the synergistic microalloying of Zr and Er not only effectively refines the grain structure but also facilitates the elimination of the δ′ phase. The addition of Er facilitates the complete transformation of the δ′ phase into the strong and ductile T1 phase, resulting in a significant enhancement of the alloy's strength and ductility. Following 100 h of aging at 120 °C, the ultimate tensile strength has increased from 373 to 457 MPa, and the elongation after fracture has risen from 2.8% to 4.9%.

In this study, particle-reinforced aluminium matrix composites (PRAMCs) of an Al–Cu–Li alloy were prepared using nano-sized TiB₂+TiC particles. The relationship between TiB₂+TiC nanoparticles and T1 precipitates during the ageing process, as well as the influence of TiC + TiB₂ particles on the growth process of T1 precipitates during the ageing process, were investigated. The grain sizes of the A0 and A1 samples were found to be 249.89 μm and 86.42 μm, respectively. The dislocation density is greater in the deformed A1 sample. The coefficient of thermal expansion (CTE) effect generated by TiC and TiB₂ particles stimulates the precipitation process of T1 precipitates. The A1 alloy reached the peak ageing state in a shorter time and yielded a greater number of T1 precipitates. The precipitation process of T1 precipitate is: SSSS→T1P→T1. The transition from T1P (face-centered cubic, FCC) to T1 (hexagonal close packing, HCP) entails a modification in the order of packing. The recently formed T1P precipitate is attached to the established T1 precipitate and extends along the c-axis through the shared copper-rich layer that has formed on both sides of the mature T1 precipitate. The mechanical properties of sample A1 are optimal at T = 22h, with a yield strength, tensile strength, and elongation of 520 MPa, 553 MPa, and 8.2%, respectively. In comparison to the A0 sample, the yield strength and tensile strength exhibited an increase of 5.05% and 5.13%, respectively.

The fatigue crack propagation (FCP) behavior of a new Al–Cu–Li alloy under different aging treatments including T3, T8, and non-isothermal aging (NIA) was investigated. It was detected that the T8-24h sample exhibited the highest FCP resistance and the best mechanical performance. Compared with the T3-40D sample, the crack paths of the T8-24h sample and the C150 (non-isothermal peak-aged) sample were more tortuous and the crack width was narrower. Furthermore, the T8-24 sample had the lowest decreased FCP rate by an order of magnitude at the stress intensity factor (ΔK) of 30 MPa·m1/2. A large number of nano-scale T1 phases were precipitated in the T8-24h sample and their number density was also increased compared with the other sample. The presence of the tiny T1 phase plays a crucial role in impeding crack propagation as it can be sheared by dislocations without accumulating damage. This resulted in a substantial improvement both in the mechanical and fatigue properties of the alloy. Moreover, in the Paris stage of FCP, factors such as the size and concentration of precipitates within the grain and grain boundary play a vital role in determining the extent of crack growth. The results of transmission electron microscopy (TEM) bright field images on grain boundaries (GBs) analysis show that the variations in strength between the grain boundary and intragranular regions have a direct influence on the alloy's susceptibility to fatigue and corrosion resistance.

T1 (Al2CuLi) nano-phase precipitation has been a major focus in developing new multi-microalloyed Al–Cu–Li alloys. Nevertheless, more understanding is required. This work investigated the effect of Zn alloying on the microstructure and mechanical properties of multi-element Al–Cu–Li alloys with a high Cu/Li ratio using a combination of advanced electron microscopy and first-principles calculations. Zn alloying (i) induced a higher density of geometrically-necessary dislocations after solid-solution treatment, which increased the T1 nucleation rate during the early aging stage; (ii) promoted T1 growth by substituting Al or Cu atoms in the T1 structure; and (iii) profoundly increased the aging kinetics, the age hardening response, and the strength. In addition, the co-segregation of Zn, Mg and Cu at the T1/Al interface helped to stabilize the fine T1 nano-platelets. These structural insights into T1 precipitation and age hardening by Zn alloying can help to guide the optimal design of high-performance Zn micro-alloyed multi-element Al–Cu–Li alloys.

The thermal stability of Al–Cu–Li alloy is critical to the quality and reliability of aerospace structural components. In this work, the microstructure and properties of rapidly solidified Al–Cu–Li alloy (T84) thermally exposed at 150 °C, 175 °C, 200 °C and 225 °C for 500 h were systematically studied. The results show that the T84 alloy exhibits excellent thermal stability with increased strength after thermally exposed at 150 °C, which is attributed to the increased number density of the T1 phase -Al2CuLi. With the further increase of thermal exposure temperature, the size of the T1 phase increases, the number density decreases significantly, and coarse precipitates such as T2 phase-Al6CuLi3 are formed. Meanwhile, the grain boundary precipitates coarsen and the precipitation free zones widen. The strengthening mechanism of the T1 phase transforms from shear mechanism to by-passing mechanism, and its contribution to yield strength decreases dramatically. In addition, the calculated activation energy indicates that coarsening of the T1 phase is controlled by the diffusion of Cu atoms.

In the present work, the anisotropic creep aging (CA) behavior and microstructural evolution of Al–Cu–Li alloy are investigated under different stress levels. The results indicate that as the stress level increases, the anisotropic creep behavior of Al–Cu–Li alloy changes significantly. As the applied stress level increases, the in-plane anisotropy (IPA) value of creep strain decreases and then increases. In addition, the strength also exhibits significant anisotropy, and as the applied stress level increases, there are differences in the strength changes of samples with different orientations at different creep aging times. Electron backscatter diffraction (EBSD), Energy-dispersive x-ray spectroscopy (EDS) and transmission electron microscopy (TEM) methods are used to study the evolution of texture and microstructure, as well as their effects on the anisotropy evolution of materials. Microscopic observation reveals that the anisotropy changes in creep and strength can be attributed to the difference in dislocation density and grain boundary slip phenomenon during the initial creep stage in samples with different orientations, as well as the stress orientation effect of precipitated phases, especially T1 phase. The study reveals a new mechanism of anisotropic CA mechanism in Al–Cu–Li alloy under different applied stress levels.

The evolution of the microstructure, texture and mechanical properties of the Al–Cu–Li alloy sheets by nanoscale TiC + TiB2 ceramic particles during solid solution treatment was systematically investigated by characterization, texture measurements and mechanical performance tests. The yield strength, tensile strength, and elongation of the A1 alloy with the addition of nanoscale TiC + TiB2 ceramic particles under T4P conditions were 312 MPa, 420 MPa, and 21.9%, respectively, which were 35.6%, 27.6%, and 2.8% higher than those of the A0 alloy, respectively. The recrystallization mechanism of both alloys was mainly the particle stimulated nucleation (PSN) mechanism, but the nanoscale TiC + TiB2 in the A1 alloy led to a stronger Zener dragging effect, which hindered the growth of CubeND nuclei, and P-oriented grains dominated. Thus, the A0 alloy sheet was dominated by CubeND components, while the A1 alloy sheet was dominated by P recrystallized grains, which led to the two alloy sheets showing opposite variation trends of the deep drawing properties with increasing solid solution treatment time. The short-time solid-solution process is more likely to provide better properties to the alloy with TiC + TiB2 added particles better properties in terms of various aspects, such as microstructure, mechanical properties, and electrical conductivity.

The precise control of forming in the new generation Al–Li alloy is challenged by the anisotropic creep aging behaviors. This anisotropy is influenced by coupling effect the microstructure and process parameters during creep age forming, where process parameters such as creep aging temperature and stress play a crucial role. Taking the 2195 Al–Cu–Li alloy as an example material, the study aimed to investigate the effect of creep aging temperatures (140–200 °C) and stresses (150–200 MPa) on the anisotropic creep aging behaviors. The findings revealed that with increasing temperature and stress, the in planar anisotropy (IPA) value of creep deformation decreased from 19.1% to 9.4%, the IPA value of strength decreased from 10.3% to 5.1%. The study uncovered the anisotropy of creep aging and its mitigation mechanisms. The analysis revealed the crucial role of the initial texture and precipitation. By regulating the type and size of precipitates, the process parameters can mitigate anisotropic creep aging behavior. The stress-oriented precipitation of GPI (θ″) zones intensifies creep aging anisotropy, while the homogeneous precipitation of T1 phase hinders creep aging anisotropy, the smaller and more uniform the T1 phase, the stronger the hindering effect. The coarsened T1 phase have a relatively small effect on creep aging anisotropy. In conclusion, the optimal combination of low deformation anisotropy (9.4%) and excellent yield strength (527 MPa) can be achieved when the creep aging temperature is set at 170 °C under 200 MPa.

This work investigated the influence of cooling rate (0.04, 0.87, 15.2 and 156.2 K/s) on the microstructure and compressive properties of Al–4Cu–3Li-0.7 Mg–1Zn alloys fabricated by several casting molds. The experiment results revealed that the microstructure cooled at low cooling rates of 0.04, 0.87 and 15.2 K/s is composed of α-Al, α(Al)+T2, θ (Al2Cu), T1 phases and core-shell configuration (Al13Fe4/Al7Cu2Fe phase). This core-shell structure is observed for the first time in an Al–Cu–Li alloy. However, T1 and core-shell configuration vanish at the high cooling rate of 156.2 K/s due to the insufficient diffusion time of Cu, Li and Fe elements. As the cooling rate increases, the average secondary dendrite arm spacing (SDAS) decreases significantly from 110.3 to 7.5 μm and the relationship between SDAS and cooling rate has been established. The average diameter/thickness of the α(Al)+T2, Al2Cu and Al13Fe4/Al7Cu2Fe phases decreases dramatically from 16.9 to 1.0 μm, 8.1 to 0.8 μm and 7.5 to 0.7 μm with the increase of cooling rate, respectively. Fine spherical Al13Fe4/Al7Cu2Fe and Al2Cu phases are beneficial to the improvement of comprehensive compressive properties. Additionally, the solute concentration in the matrix decreases, while the hot-tear resistance and volume fraction of secondary phases increase with increasing cooling rate. The empirical equations are established between (compressive properties, SDAS) and cooling rate. The fracture failure is responsible for the initial hot tearing at low cooling rates, the α(Al)+T2 or Al2Cu or Al13Fe4/Al7Cu2Fe phases at the moderate cooling rate, and the α(Al)+T2 phase at the high cooling rate.

In this study, the effect of Sc content on the microstructural characteristics and phase evolution of an Al–Cu–Li alloy under as-cast and homogenization conditions was investigated. The results show the grain refinement effect was distinct when the content of Sc was 0.16 wt%. However, further increased in Sc content resulted in a limited decrease in grain size. Besides, In the 0.16Sc alloy, the flocculent phase with primary Al3(Sc,Zr) phase coexisting with W (Al8-xCu4+xSc) phase appeared, and in the 0.32Sc alloy, the additional blocky primary Al3(Sc,Zr) phase was observed. With the increased of Sc content, the proportion of primary Al3(Sc,Zr) and W phases gradually increased, and the number and size of Al2Cu and Ag-containing Al2CuMg phases at grain boundaries gradually decreased. Two different morphologies of the primary W phase, flocculent and long strip shaped, were revealed within the Sc-containing alloy. The formation of the core-shell structure formed by Al3(Sc,Zr) particles and W phase was generated by the peritectic-eutectic reaction (Liquid + Al3(Sc,Zr)→α-Al + W) and the long strip of W phase was generated by the eutectic reaction (Liquid→α-Al + Al2Cu + W). During the homogenization process, the Al2Cu and Ag-containing Al2CuMg phases were completely re-dissolved after the two previous stages of homogenization, and only a small amount of the spheroidal residual W phase persisted. A subsequent low temperature treatment was employed to allow the Sc atoms that had diffused into the Al matrix to precipitate as Al3(Sc,Zr) dispersoids, resulting in a higher number density of Al3(Sc,Zr) particles for more efficiently utilizing the Sc elements.

Precipitation-strengthened Al–Cu–Li alloys are commonly used as structural materials in aerospace equipment. The present work focused on investigating the characteristics of grain boundary T1 precipitate in a rolled Al–Cu–Li alloy. It was found that the T1 phase with a multilayer structure will precipitate at the grain boundary after artificial aging, and it is nearly continuously distributed along grain boundaries in the pre-rolled samples. The habit plane of the intergranular T1 normally parallels a (111) plane of the matrix on one side of the grain boundary. And compared to the preferential growth of platelet edges for the intragranular T1, the grain boundary T1 phase is also prone to thickening via the stacking of successive unit-cell-thick (0.935 nm) layers on the existing broad surface of the plate, resulting in the significant coarsening in the direction perpendicular to its habit plane. In addition, the reason for the obvious thickening of the grain boundary T1 phase was also discussed.

Al–Cu–Li cast alloy components also show a promising application in the aerospace industry due to their relatively good combination of density and performance. According to the conventional processing procedures for cast products, a novel cast Al–Cu–Li alloy was directly solution treated and aged after homogenization, then the aging precipitation behavior and its effect on the mechanical properties of the alloy were investigated in this article. It was found that the naturally aged precipitates are rapidly dissolved during artificial aging at 175 °C, and the cubic phase, θ′ phase, T1 phase, Ω phase, and S phase will precipitate successively. In the early stage of artificial aging, the cubic phase and θ′ phase are formed prior to the T1 phase. With the aging time increasing, numerous T1 phases also precipitate with relatively large diameters, so the hardness of the alloy keeps rising until to the peak value. The naturally aged specimens show good plasticity and relatively low strength. After artificial aging, the tensile strength of the cast alloy can be increased to 423 MPa, but the corresponding elongation has a significant reduction. Moreover, the predominant precipitates—T1 phase and cubic phase show excellent thermal stability during 175 °C aging, they still exist with a large population even aged for 40 days.

The local tensile mechanical properties of laser beam-welded joints of AA2198 alloy with Al–Si filler wire were experimentally investigated. For this purpose, micro-flat tensile specimens were extracted from the fusion zone and the heat-affected zone. The chemical composition of the filler wire affects the local mechanical properties in the fusion zone, showing an approximately 26% decrease in yield strength from the radiation exposure side to the weld root side. The effect of post–weld heat treatment on the tensile mechanical behavior was additionally investigated for different heat treatment artificial ageing conditions. The maximum yield strength increase was noticed for 48 h of artificial ageing for the weld root side of the fusion zone. Several approximations were proposed to correlate the hardness measurements with the local tensile mechanical properties of the welded joint that allow for a fast assessment of the global tensile mechanical behaviour of the welded joint. To evaluate the effect of (i) artificial ageing and (ii) geometrical imperfections of the weld on the mechanical behavior of the welded joint, finite element analyses were performed, using the local mechanical properties as input to the model. It is shown that the local mechanical properties of the fusion zone play a pivotal role on the strain localization and fracture of the welded joint.

Pre-rolling deformation is a preferable procedure in practice, compared to pre-stretching, to improve the performances of the rolled Al–Cu–Li plates. In the present work, the different strains of pre-rolling were applied to a rolled Al–Cu–Li alloys before aging. The influence of pre-rolling on mechanical properties and precipitates during 200 °C aging was carefully investigated through hardness test, tensile test, and microstructure characterization. It was found that the aging precipitation behavior was rather complicated for the not pre-rolled samples, various abnormal precipitates were precipitated along with the large diameter and low-density of T1 (Al2CuLi) phase after a period of aging. After pre-rolling, the nucleation of T1 phase was greatly promoted while the formation of other phases was inhibited, resulting in the precipitation behavior became dominated by the high density and tiny T1 phase. Furthermore, the precipitation kinetics of the T1 phase was continually accelerated by increasing the pre-stain, which facilitated the more rapid aging response, higher T1 phase density and continuous improvement of mechanical properties. The strain of pre-rolling could be increased to 20% to obtain the optimal properties, and the tensile strength of the 20% pre-rolled samples increased to ∼520 MPa in peak aged state, compared to ∼360 MPa of the samples only T6 tempered.

A 2297 aluminum-lithium alloy was subjected to multi-axial compression (MAC) at 160 °C to obtain different cumulative strains. The room temperature tensile test, transmission electron microscopy and X-ray diffraction techniques were used to study the microstructural evolution and mechanical properties of Al–Cu–Li alloy. It was observed that the ultimate tensile strength was increased from 267 MPa to 480 MPa and the hardness was increased from 55 HV to 141 HV by high-density dislocations and precipitation phases. Due to the massive amount of precipitation occurring at dislocations and the subsequent high strain introduced to destroyed it, the size of the precipitates was effectively reduced, the fine precipitates delayed the strain localization, the alloy obtained high elongation (~11.2 %).

The effects of double-step homogenization processes on the precipitation of Al3Zr dispersoids and the dissolution of the primary phases of 2196 aluminum alloy were studied by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was revealed that first-step homogenization facilitates the nucleation of Al3Zr, while second-step homogenization results in the dissolution of the primary phases and the growth of Al3Zr dispersoids. The nanosized θ’ precipitates formed in the first-step homogenization are dissolved after the second-step homogenization. The optimum homogenization process was selected as 400 °C/10 h + 520 °C/24 h, which effectively dissolves the primary phases and promotes the formation of refined distribution of Al3Zr dispersoids. This phenomenon is mainly caused by the highest nucleation rate of the Al3Zr phase at 400 °C. While reducing the heating rate of the homogenization process can increase the number density of the Al3Zr dispersoids and reduce the precipitate free zone (PFZ), it does not alleviate the inhomogeneity of the Al3Zr precipitation. These results are expected to be meaningful for tailoring the industrial homogenization processing of as-cast Al-Cu-Li alloy.

Aluminum (Al)–copper (Cu)–lithium (Li) alloys are susceptible to environmental degradation, which limits the in-service lifetime of the components. Because of their complex composition, there are seldom studies focusing on corrosion behavior influenced by one single element, which is essential to clarify the corrosion mechanism. Herein, the sole influence of Mg on the corrosion behavior of Al–Cu–Li–xMg alloys was analyzed. Results revealed that the addition of Mg can affect the nucleation and precipitation process of the T1 precipitate, resulting in a difference of potential between grain interior and grain boundary. The precipitation of the T1 precipitate was promoted in a 0.7Mg alloy while impeded in a 1.1Mg alloy, due to the competition of Cu atoms and nucleation sites between T1 and S′. Two types of corrosion behavior of Al–Cu–Li–xMg alloys appeared due to the potential difference and continuity of grain boundaries. Continuous precipitates in grain boundaries and less precipitates within the grain are likely to cause intergranular corrosion (IGC), while more precipitates within the grain will result in pitting.

In this work, the effects of Ce content (0.1%, 0.2%, and 0.3 wt%) on the microstructures and mechanical properties of Al-Cu-Li alloys were investigated. The results show that the grains of Al-Cu-Li alloy are refined by adding Ce element. When Ce content is less than 0.1%, the ultimate strength of the alloy increases with the increase of Ce content. However, the ultimate strength of the alloy decreases when Ce content is above 0.1%. For Al-Cu-Li alloy with different Ce content, the aging precipitation of T1 and θ′ phases play the main strengthening role. When Ce content increases from 0.1 to 0.3%, dynamic recrystallization is promoted during hot deformation. The recrystallization of the alloys is inhibited after T6 treatment with the increase of Ce content, which can be attributed to existence of the Al8Cu4Ce phases on the grain boundary. This work provides an economical and convenient method for improving the properties of Al-Cu-Li alloys by Ce addition.

The objective of this study was to develop the technology of butt friction stir welding (FSW) for Al–Cu–Li alloy sheets of 1.4 mm thick after hot rolling and subsequent quenching. This initial state of the alloy was chosen in order to provide heat treatment of the received joints after FSW. The TEM observation was performed for the base material and different zones of the joints in order to determine the precipitates and dislocations density and distributions. The grain size in the stir zone (SZ) was increased; the width of the softened region was narrowed down with the decreasing of linear energy. The differences in mechanical properties of the FSWed joints were explained by analysis of microstructural changes and tensile fracture surfaces, supported by the results of the numerical simulation of the temperature distribution and material flow. The fracture of the high linear energy FSW joints occurred in the SZ along the remnant oxide line (ROL), while the low linear energy FSW joint raptured in the transition between HAZ and TMAZ on the AS, where lower hardness value was detected.

Cryogenic deformation can improve the strength and plasticity of Al–Li alloy, although the underlying mechanism is still not yet well understood. The effects of cryogenic temperature on the tensile properties and microstructure of an Al–Cu–Li alloy were investigated by means of tensile property test, roughness measurement, scanning electron microscope (SEM), optical microscope (OM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The results indicated that the strength and elongation of the as-annealed (O-state) and solution-treated (W-state) alloys increased with the decrease in deformation temperature, where the increasing trend of elongation of the W-state alloy was more significant than that of the O-state alloy. In addition, a temperature range was observed at approximately 178 K that caused the strength of the W-state alloy to slightly decrease. The decrease in temperature inhibited the dynamic recovery of the Al–Cu–Li alloy, which increased the dislocation density and the degree of work hardening, thus improving the strength of the alloy. At cryogenic temperatures, the internal grain structure was more involved in the deformation and the overall deformation was more uniform, which caused the alloy to have higher plasticity. This study provides a theoretical basis for the cryogenic forming of Al–Li alloy.

In this work, a Al-Cu-Li alloy plate with outstanding mechanical properties was successfully prepared with electromagnetic twin-roll casting (TRC) technology. The microstructure of Al-Cu-Li alloy manufactured by conventional mold casting, TRC, and electromagnetic TRC was studied in detail. The action mechanism of electromagnetic oscillation field (EOF) in the TRC process was studied by systematic experimental characterization and numerical simulation. The results show that the EOF will enlarge the circumfluence area in the cast-rolling zone, accelerate the mass transfer and heat transfer in the molten pool, and make the solute field and flow field in the liquid cavity tend to be evenly distributed. Further, the introduction of the EOF will produce the electromagnetic body force F with the maximum strength of 14 N/m3. The F acting on the solidification front will eliminate the accumulation and deposition of Cu2+, Li+, Mg2+, Zn2+, Mn2+ at the dendrite tip and inhibit the growth of dendrites. At the same time, the F can refine the microstructure of the TRC plate, promote the formation of equiaxed crystals, improve the supersaturated solid solubility of solute elements in the α(Al) matrix, and avoid the appearance of obvious solute segregation area or the formation of excessive solute enrichment area. Therefore, the macro-segregation in TRC plate was significantly reduced, the solidification structure was dramatically refined, and the comprehensive properties of the alloy were remarkably improved.

The mechanical properties and microstructure evolution of an Al-Cu-Li alloy sheet processed via hot rolling (HR) (at 400 °C and 500 °C) or cryorolling (CR) (at −100 °C and −190 °C) and subsequence aging at 160 °C for 10 h were investigated. Before aging, the highest ultimate tensile strength of 502 MPa was achieved when the sheets were cryorolled at −190 °C, while the better ultimate tensile strength of 476 MPa and the best elongation rate of 11.1% was achieved simultaneously when the sheets were cryorolled at −100 °C. The refined grains and numerous uniform deformation-induced dislocations microstructures were responsible for the improved strength and enhanced ductility of the cryorolled sheets compared to that of the alloy processed by hot rolling with a low dislocation density zone (LDDZ) and high dislocation density zone (HDDZ). After aging at 160 °C for 10 h, the ultimate tensile strength further improved resulted from the greater precipitation strengthening, and the increased precipitates provided greater resistance to dislocations movement resulting in the increased ductility although the dislocation density decreased. The uniform dislocation microstructures in the cryorolled sheets provide numerous nucleation sites for the precipitates, leading to higher strength after aging.

After aging heat treatment, Al-Cu-Li alloy, in general, contains a variety of precipitated phases that jointly influence the age-strengthening effect on the alloy. In this work, a multiphase-coupled strengthening model has been established on the basis of a dislocation bypassing mechanism. The model considered situations with different proportions of two strengthening phases, T1 and θ′, and then obtained the dimension and volume fractions of these two strengthening phases via experiments. The values predicted by the multiphase-coupled strengthening model and the classical strengthening superposition model were compared with the measured results. The multiphase-coupled strengthening model established in this work had better consistency with the measured results. Moreover, the modeling method proposed in the paper can also be extended to the system having over two primary strengthening phases. Hence, the model can contribute towards the development of a multi-component precipitation strengthening process for aluminum alloys.

The effects of the addition of 0.29 wt % Ce on the recrystallization behavior of an Al⁻Cu⁻Li⁻0.13Zr (wt %) alloy during isothermal annealing were investigated. Ce addition greatly improved inhibition of recrystallization in this alloy compared with that in the Ce-free alloy. The texture of the Ce-containing alloy contained a large amount of β-fibers and fibrous unrecrystallized grain microstructures distributed along the rolling direction in the overall annealing process. The improved recrystallization resistance endowed by Ce addition can be attributed to the large number of small Al8Cu4Ce species formed on the grain boundary. These fine particles with high-temperature stability can exert a Zener pressure on the Al3Zr dispersoid-free grain boundary. The yield strength of the Ce-containing alloy increased significantly, to 38 MPa, and the fracture toughness improved by 56.28% compared with those of the Ce-free alloy. This work provides a convenient and economical method for enhancing the overall performance of an Al⁻Cu⁻Li⁻Zr alloy via recrystallization inhibition by Ce addition.

The microstructural evolution and properties of an Al-Cu-Li alloy with Mg and Zn microalloying (Al-3.5Cu-1.5Li-0.5Mg-0.4Zn-0.3Mn-0.12Zr-0.06Ti) ingot subjected to homogenization (second-step annealing at 500 °C for 24 h following first-step annealing at 400 °C for 8 h) were investigated. Mg-Zn atom clusters were enriched at the end of dendrites as well as low-melting eutectic phases such as S (Al2CuMg), T2 (Al6CuLi3), TB (Al7.5Cu4Li) and T1 (Al2CuLi) in the as-cast alloy. During homogenization, Mg-Zn atom clusters diffused from the segregation to the vacancies, leading to the dissolution of the low-melting eutectic phases. Not only Al3Zr particles were observed at 500 °C, but more fine and uniform spherical dispersoids appeared, which were assumed as Al3(ZrxTiyLi1−x−y). Mg and Zn microalloying can promoted the nucleation of Al3Zr and Al3(ZrxTiyLi1−x−y) dispersoids, as well as T (Al20Cu2Mn3) phases, which all inhibited recrystallization effectively and improve the uniformity of the grains due to the strong pinning effect. The yield ratio was decreased from 0.81 to 0.52 with the yield strength decreased from 172 MPa to 61 MPa, which showed better plastic deformation ability of the alloy subjected to homogenization. In addition, the dissolution of low-melting eutectic phases and formation of Al3(ZrxTiyLi1−x−y) dispersoids resulted in the significant improvement on thermal stability.