Precipitation Of T1 Phase Research Articles

Achieving high mechanical and corrosion properties of AA2050 Al-Li alloy: The creep aging under plastic loading

The influences of elastic/plastic loading (100–220 MPa) on the creep behavior, mechanical properties, and corrosion behavior of creep-aged AA2050 alloys were investigated. The results show that the creep rate increased from 0.35 % to 0.61 % with the increase of stress from 100 MPa to 220 MPa. The creep rate was increased rapidly under plastic loading (220 MPa) due to the increased dislocation density. Meanwhile, the plastic loading shortened the peak-aged time of creep-aged alloys and achieved outstanding strength (UTS=534 MPa, YS=496 MPa, peak aged), which increased by 33 MPa and 32 MPa compared with elastic loading, respectively. The strength enhancement was attributed to the increase in dislocation density, weak oriented precipitation effect, and dense precipitation of T1 phases. Additionally, compared with elastic loading, GBPs under plastic loading coarsened and distributed discretely, their elements content distributed evenly, and the Cu content increased. Therefore, the intergranular corrosion (IGC) depth and stress corrosion cracking (SCC) susceptibility index (ISSRT) decreased from 174 μm, and 8.7 % to 121 μm, and 5.9 %, respectively. These findings pave a way in breaking curvature limit of creep aging technology.

Effect of pulse current density on creep ageing behavior of 2195 Al-Li alloy

Electrical pulse-assisted creep ageing forming can effectively improve the mechanical properties and forming efficiency of large aluminum components. However, it is difficult to achieve uniform and consistent current density at different positions in complex components. Thus, the creep behavior, mechanical properties, and microstructure evolution of 2195 Al-Li alloy under three pulse current densities (0A/mm2, 3A/mm2 and 8A/mm2) was systematically studied. The experimental results showed that the creep deformation increases with increasing current density during the 1st hour stage of electric pulse-assisted creep ageing process. However, the total creep strain of 8 h shows a trend of decreasing and then increasing. Low density pulsed currents (non-thermal effect) can promote the precipitation of the T1 phases and θ′ phases, and narrow the precipitates free zone compared to conventional creep aged sample (0A/mm2). High density (Both of non-thermal effect and Joule heating effect) pulsed currents can promote the precipitation of T1 phases, inhibit θ′ phases and form the precipitated phase penetrate the grain boundaries. A gratifying finding is that an increase in current density accelerates the aging hardening process, but the peak strength after creep ageing is the same for different current densities. This indicates that high pulse current density can improve creep ageing forming efficiency and ageing hardening process, and can use non-uniform current densities to solve the problem of significant differences in overall structural component formability while maintaining final performance consistency.

Effect of pre-deformation on microstructure and mechanical properties of 2050 Al−Li alloy

The microstructural evolution and mechanical properties of 2050 Al−Li alloy subjected to different rolling pre-strains (0−20%) and aging (T8) were studied. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the microstructure. The results show that the grains were significantly refined along the normal direction (ND) and the intragranular distortion increased with the increase of pre-strain level. The entanglement of defects, e.g., dislocations, provides a large number of nucleation sites for the precipitation of T1 phases. This leads to larger number of precipitates and narrower distance between precipitates, thus improving the hindering effects on dislocation motions and the strength of the alloy. When the pre-deformation level reaches 16%, the alloy shows the highest density of T1 phases and strength (the yield strength and tensile strength reach 568 and 584 MPa, respectively, and elongation is 8.6%). When the amount of pre-deformation is further increased to 20%, the atomic diffusion channels are reduced due to dislocation entanglement, and the reduction in the number of T1 phases eventually leads to a decrease in strength of the alloy.

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.

Microstructural evolution and mechanical properties of the rapidly-solidified and hot-extruded 2196 Al-Li alloy

The microstructural evolution and mechanical properties of the 2196 Al-Li alloy prepared by the vacuum gas atomization, hot-isostatic-pressing (HIP) and hot-extrusion were investigated. The results show that prior particle boundaries (PPBs) exist in the microstructure of the HIPed alloy, and hot-extrusion effectively breaks PPBs to restrict the element micro-segregations. The as-extruded alloy exhibits fine grains, and bears higher solution treatment temperature due to the absence of low-melting-point micro-segregations. In the ageing process, the alloy hardness continues to rise, and reaches the peak value at 48 h. The precipitation sequence of the alloy is determined to be: supersaturated solid solution (SSS) → GP zone + fine T1 + δ′ → T1 + θ′ + δ′, where T1 phase dominates the whole ageing process. The diameter of the T1 platelets increases gradually with the increase of ageing time, meanwhile the T1 number density slightly drops in the over-aged alloy. The 3% pre-stretching promotes the nucleation of T1 phase, and the peak-ageing time is shortened to 28 h. Besides, no over-ageing phenomenon is observed in the pre-stretched samples. The Mg-Cu and non-Cu clusters formed on the dislocations accelerate the precipitation of T1 phase and prevent the nucleation of θ′ phase. The yield strength (YS) and ultimate tensile strength (UTS) of the T8 sample are 490 MPa and 515 MPa, respectively, which is notably higher than the T6 sample. The tensile strength of the present alloy is relatively higher than that of the Al-Li alloys with a comparable Li content.

Enhancing creep formability and mechanical properties of creep-aged AA2050 alloys via slow heating

In this work, a new creep aging route (pre-deformation+slow-heated creep aging, PSHCA) of AA2050 alloys was developed by the slow heating (20 °C/h) from 120 °C to 180 °C. The PSHCA alloy exhibits high creep strain with a simultaneous increase of strength and plasticity. The yield strength, ultimate tensile strength, and elongation reached 544 MPa, 581 MPa, and 11.1%, respectively. Both the rolling pre-deformation before aging and stress field during aging promoted the increased dislocation density and dense precipitation of T1 phases in the aged alloys, hence, the strength was improved at the expense of plasticity. Meanwhile, the bimodal diameter distribution of T1 phase of the PSHCA alloy and the enrichment of Ag atoms at T1/matrix interface was promoted by slow heating, slowing down the thickening of T1 phases. This further promoted the plasticity of PSHCA alloys while maintaining high strength. Additionally, the slow precipitation of T1 phase at the early stage of aging promoted dislocation slip and thus improving the creep strain of PSHCA alloys. These findings pave a way in designing large-curved and high-performance Al-Li components by creep aging technology.

Influence of aging treatment on corrosion behavior of extruded 2195 Al−Li alloy

The 2195 Al-Li alloy was processed by under-aging (UA), peak-aging (PA), double-aging (DA) and retrogression re-aging (RRA) treatments, and the microstructure, intergranular corrosion (IGC), exfoliation corrosion (EXCO) and stress corrosion cracking (SCC) behaviors were observed and discussed. The results show that the sequence of IGC and EXCO resistance is: RRA > UA > DA > PA. The low corrosion resistance of PA and UA is mainly caused by the continuous precipitation of T1 phases at grain boundaries to form continuous corrosion channels, while the interruption of corrosion channels caused by coarse and discontinuous T1 phases and wider precipitate free zone is the reason for the best corrosion resistance of RRA. The RRA alloy exhibits the best SCC resistance, and the order of SCC resistance is: RRA > DA > UA > PA. The discontinuous precipitation of intergranular T1 phases promotes the propagation of corrosion cracks across grain boundaries, thereby improving the SCC resistance.

Microstructural evolution and hydrogen content and their effect on properties of TiB2/Al-Li-X composites with different Li contents

The content and proportions of the major solute elements in aluminum matrix composites are critical to the microstructure and properties of the material. This paper uses a stepwise method based on ultrasonic in-situ casting technology to prepare TiB2/Al-Li-X composites with different Li contents (0.5–3.0 wt%). The composites' microstructure morphology, precipitates, hydrogen content, and mechanical properties were tested and analyzed. The results showed that with the increase of Li content, the number of θ′ phases decreases, the number of δ′ phases increases, while the number of T1 phases increases and then decreases, and the TiB2 particles promote the precipitation of T1 phases at low Li content; meanwhile, the hydrogen content keeps increasing, and the grain size decreases and then increases. The increase of the T1 phase and the decrease of grain size enhance the strength of the composites, while the increase of δ′ phase and hydrogen content increase the hardness but decrease the plasticity. When the Li content is around 1.5 wt%, the grain size is minimized, the TiB2 particles are fine and dispersed, the yield strength reaches the maximum value of 166.9 MPa, and the mechanical properties are relatively balanced.

Origin and effect of anisotropy in creep aging behavior of Al–Cu–Li alloy

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.

Effect of Zr addition on the microstructure evolution and mechanical properties of extruded Al-Cu-Li-Mn alloys

The effects of Zr addition on microstructure evolution and mechanical properties of extruded Al-Cu-Li-Mn alloy were investigated during heat treatment processing. The recrystallization and grain growth were profoundly inhibited in solid solution-treated (SST) Al-Cu-Li-Mn-Zr alloy (Zr-containing), and massive substructures were retained, which were attributed to the higher Zener pinning pressure provided by Al3Zr dispersoids. But, complete recrystallization and considerable grain growth occurred in SST Al-Cu-Li-Mn alloy (Zr-free). Besides, the deformation textures containing Brass and S components were predominant in Zr-containing alloy, which contributed to a higher average Talyor factor (M) value. The higher strength behavior in SST Zr-containing alloy mainly originated from the extra Al3Zr dispersoids apart from the higher M value and dislocation density. The higher dislocation density and Al3Zr dispersoids in Zr-containing alloy promoted the precipitation of T1 phases and narrowed the width of precipitate-free zones (PFZs). Compared with Zr-free alloy, the enhanced combination of good strength and ductility shown in T6-aged Zr-containing alloy was mostly due to the higher T1 phase density and M value, higher dislocation density, and extra Al3Zr dispersoids.

A comparative study on precipitation behavior of a sand-cast Al–Li–Cu alloy with the different quenching rates

The performance of large-size structural components with varied wall thickness is mainly determined by the quench sensitivity, while there was a blank of the studies on the quench sensitivity of cast Al–Li alloys. In this study, the precipitation behavior of sand-cast Al–2Li–2Cu-0.5Mg-0.15Sc-0.15Zr-0.05Ti alloy subjected to different quenching conditions in room temperature water, boiling water and air was compared. The effect of the quenching rates on the formation mechanisms of δ΄ (Al3Li) and T1 (Al2CuLi) precipitates was discussed. It was found that a rapid quenching rate facilitated the precipitation of T1 phases and the refinement of δ′ phases, which contributes to the improvement of the mechanical properties. During the subsequent ageing, the strength and ductility were enhanced with the quenching rate increasing, but the strength did not vary by more than 15%, indicating that the sand-cast Al–Li–Cu alloy owns a lower quench sensitivity. This work is expected to enlighten the understanding of the evolution mechanisms of precipitates during quenching and provide a reference for the heat treatment of complex structural components for cast Al–Li alloys.

Effect of minor Sc additions on precipitation and mechanical properties of a new Al-Cu-Li alloy under T8 temper

The effects of minor Sc additions on the formation of various precipitates and mechanical properties of a new Al-Cu-Li alloy have been experimentally investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), three dimensional atomic probe (3DAP) analysis and tensile tests. Under T8 temper, the introduction of 0.092 wt% Sc accelerates the aging response of Al-Cu-Li alloy and induces a little reduction in the tensile and yield strength due to the decrease of solid solubility of Cu in Al alloy matrix and number density of T1 (Al2CuTi) strengthening phase, which are closely linked with the formation of insoluble Sc-containing W(AlCuSc) phase by consuming Cu solutes for the precipitation of T1 phase. Except for T1 and W phase, Nanoscale Al3(Sc,Zr) and S′ phases are also found after minor Sc addition. The 3DAP tomography indicates that the Al3(Sc,Zr) precipitates have a core-shell structure with Zr atoms mainly close to the shell and Sc atoms enriched in the core. It is believed that such precipitate is only probably composed of Al and Sc at the initial stage, and then Zr enters into them at the later stage, which hinders the diffusion of Sc in the matrix through the boundary into the interior of the particle and thus makes the coarsening rate of Al3Sc decrease.

Deformation microstructure and thermomechanical processing maps of homogenized AA2070 aluminum alloy

The hot deformation behavior of homogenized AA2070 Al–Li–Cu alloy was studied using isothermal compression in a temperature range of 300 °C–500 °C and a strain rate range of 0.001 s-1 to 1 s-1. Deformation microstructure was characterized using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) including weak beam dark field STEM imaging to correlate the microstructure evolution with hot deformation mechanism. TEM/STEM results show that a high density of fine T1 (Al2LiCu) phase forms in the microstructure through dynamic precipitation at compression temperatures lower than 400 °C, especially at low strain rates. Constitutive analysis shows that back stress due to dynamic precipitation of T1 phase decreases with increasing compression temperature and increasing strain rate. EBSD characterization indicates that dynamic recovery is the main softening mechanism at temperatures below 400 °C. At 400 °C and above, intermetallic phases including T1, Al20Cu2Mn3 and Al3Cu2 in the microstructure gradually dissolve, and dynamic recrystallization becomes the dominant softening mechanism, resulting in texture weakening and grain refinement. Three dynamic recrystallization mechanisms including discontinuous dynamic recrystallization (DDRX) at large angle grain boundaries, particle stimulated nucleation (PSN) and continuous dynamic recrystallization (CDRX) were observed. Based on hot work efficiency, deformation instability and microstructure evaluation, processing maps were constructed using both conventional method and Garofalo sinh equation, providing optimum processing conditions (temperature >400 °C and strain rate <0.1 s-1) for industrial forging, extrusion and rolling processes.

Effect of increased stretching deformation at cryogenic temperature on the precipitation behavior and mechanical properties of 2060 Al–Li alloy

A three-step process, which involved solution treatment, stretching deformation at cryogenic temperature, and artificial aging treatment, is a potential route to fabricate complex shaped thin-walled components of aluminum alloy. This study analyzed the influence of the cryogenic stretching deformation on subsequent aging behavior and mechanical properties of 2060 Al–Li alloy. The results showed that more dislocations accumulated in the sample with a larger deformation due to the suppressed dynamic recovery rate at low temperature, which provided more nucleation sites for the precipitation of T1 phase, thus leading to a markedly homogeneous distribution. The increased number of T1 phase consumed many copper atoms in aluminum matrix, which resulted in the decrease of the nucleation and growth rate of the θ′ phase. Optimized after-aging mechanical properties were obtained by increasing the stretching strain to 16%, with a yield strength of 538 MPa, an ultimate strength of 560 MPa, and a fracture elongation of 10.1%. The high strength resulted from the combination of precipitation strengthening and retained dislocation strengthening. The reason why the alloy still maintains a high ductility after being subjected to a larger stretching deformation was its high homogeneous deformation ability at cryogenic temperature. The further increase of the deformation resulted in the formation of defects, such as slip bands, and micro-cracks in the sample, leading to decreased after-aging ductility.

Microstructural evolution and properties of electromagnetic cast-rolled novel Al–Li alloy under different heat treatment procedures

A large number of dislocations and dislocation tangles are induced in the Al–Li alloy after 5% pre-stretching deformation before aging treatment, which increases the density of the defects in α(Al) matrix and affects the competitive precipitation relationship and precipitation behavior of δ′ (Al3Li), S′ (Al2CuMg) and T1 (Al2CuLi) precipitates during the aging process. The increase of crystal defects such as dislocations provides superior nucleation sites for the heterogeneous nucleation and promotes the precipitation of T1 phase, greatly improving the mechanical properties of the alloy. The uniform and dense precipitation of T1 phase in the grain reduces the potential difference between the grains and the grain boundaries. Therefore, not only does it reduce the driving force of intergranular corrosion (IGC), but also decreases the difference of the corrosion rate between the grain boundary and intragranular. These are beneficial to slow down the corrosion process and promote uniform corrosion. The intermittently distributed grain boundary precipitates (GBPs) in the T8 treated alloy cut off the continuous corrosion channel at grain boundaries and hinder the IGC process. Furthermore, the width of the precipitation free zones (PFZs) in the T8 treated alloy is narrow. Hence, the alloy exhibits excellent IGC resistance and superior corrosion protection performance under T8 single aging treatment. The pre-aging process in low temperature before T8 single aging treatment greatly enhances the precipitation driving force of T1 phase and effectively promotes the precipitation of T1 phase in the subsequent high-temperature aging process, which further increases the strength and improves the IGC resistance of the alloy.

Corrosion behaviour of 2A97-T8 Al-Cu-Li alloy extrusion

In the present study, correlative corrosion testing and electron microscopy, including quasi-in-situ electron microscopy, are employed to investigate the corrosion behaviour of 2A97-T8 Al-Cu-Li alloy extrusion in 3.5 wt% NaCl solution. It is found that the corrosion behaviour of the alloy is influenced by synergetic effect of the plastic deformation introduced by the thermomechanical processing during alloy fabrication and the precipitation of T1 phase during T8 treatment. Localized corrosion initiates and propagates preferentially within non-recrystallized regions of the partially recrystallized alloy. Corrosion initiated at coarse constituent intermetallic particles is confined to its periphery, which doesn’t develop further when the particles are disconnected from alloy matrix.

Enhanced matrix precipitation of T1 (Al2CuLi) phase in AA2055 Al–Li alloy during stress aging process

Attempts to improve the strength of Gen3 Al–Li alloys without obviously deteriorating the ductility have been directed towards enhancing the matrix precipitation of T1 phase and reducing its enrichment at sub-grain boundaries. In this study, a novel artificial aging treatment during which uniaxial tensile stress was applied has been carried out on the AA2055 Al–Li alloy while a certain temperature was maintained. The microstructure, fractography, dislocation density, and the mechanical properties were analyzed by HAADF-STEM, HRTEM, DSC, SEM, FWHM of XRD patterns, and tensile tests. It was found that matrix T1 precipitation could be enhanced at the expense of θ’ phase by the stress applied. The enrichment of T1 phase at sub-grain boundaries could be observed in all specimens. However, the degree decreased as the pre-stretch and the applied external stress imposed. A good combination between strength and ductility was obtained for the specimen aged in T8SA100 temper (2% pre-stretch, 155 °C, 24 h, 100 MPa) and the average YS, UTS, and EI were 623 MPa, 649 MPa and 10.5%, respectively. The dislocation density in the stress aged specimens was higher than that in the stress-free aged specimens, indicating that the dislocation mechanism plays an important role in the enhanced T1 matrix precipitation during stress aging. The present study suggests that the novel stress aging treatment has great potential in improving the overall performance of advanced Al–Li alloys.

Sluggish precipitation strengthening in Al–Li alloy with a high concentration of Mg

The influence of different Mg concentrations on the mechanical properties and microstructure of an Al–Li alloy was studied. The highest Mg content was up to 1.1 wt.%. To the best of the authors knowledge, alloys with such a high Mg content has not been reported in the literature. The mechanical properties, yield strength and elongation at failure, of all of the alloys were investigated by tensile tests. Characterisation of the precipitates by analysing the dark field images and related diffraction patterns revealed that precipitation of the T1 phase (Al2CuLi) was retarded by high (1.1 wt.%) Mg concentration. We hypothesized that a competition between the precipitation of T1 phase and S' phase in high Mg containing alloy caused sluggish precipitation phenomenon and associated strengthening.

Role of Cu on the mechanical properties and microstructures evolution of Al-xCu-1Li-0.4Mg–1Zn-0.1Zr alloys

In this paper, mechanical properties and microstructures of the cast and extruded Al-xCu-1Li-0.4Mg–1Zn-0.1Zr alloys (x = 2.0, 3.0, 4.0, 4.5, 5.5, 6.5 wt%) were investigated. The results showed that the as-cast micrographs of alloys with different Cu content primarily consist of dendritic α-Al grains, and the intermetallic phases at the grain boundaries were Cu and Zr rich phases. After solution treatment, no recrystallization took place in extruded alloys, and the alloys mainly represented mixed textures composed of <111> and <100> fibers. Cu significantly affected the precipitation behavior of the extruded alloys. Only T1 (Al2CuLi) phases were observed in T6 (aging at 175 °C for 32 h) and T8 (3% pre-strain followed by aging at 150 °C for 32 h) treated alloy with 2 wt% Cu. Further increasing Cu contents (4.5 and 6.5 wt%) enabled the co-precipitation of T1 and θ' (Al2Cu) phases, as well as increased their density. In addition, the microstructures of grain boundaries of alloys with different Cu content showed dramatic differences. T1 phases precipitated at the grain boundaries of alloy containing 2 wt% Cu, while rare precipitation of T1 phases was observed at the grain boundaries of alloy with 6.5 wt% Cu. The yield strength (YS) of the alloys increased with the Cu content and the elongation (EL) showed an opposite trend. A good combination of ultra-high strength (YS = 684 MPa, ultimate tensile strength = 726 MPa) and ductility (EL = 6.3%) was obtained in T8 treated alloy containing 4.5 wt% Cu. The presence of the undesired coarse T2 (Al6CuLi3) phases at the grain boundaries resulted in the premature failure of the high Cu content alloys.

Corrosion mechanism of T1 phase in Al-Cu-Li alloy: First-principles calculations

First principle calculations in the framework of density functional theory are performed to calculate the T1 phase (Al&lt;sub&gt;6&lt;/sub&gt;Cu&lt;sub&gt;4&lt;/sub&gt;Li&lt;sub&gt;3&lt;/sub&gt;), which is the main precipitation in Al-Cu-Li alloy. In this paper, the surface energy values and surface electron work functions of different termination surfaces in T1 phase are calculated. Meanwhile, the effects of stress and common alloying elements on the T1 phase are also discussed. There are 10 different termination surfaces for T1 phase. The surface energy varies between 0.59 and 1.28 J·m&lt;sup&gt;–2&lt;/sup&gt;. It is found that the surface energy is dependent on the atomic configuration of the surface. The relaxation of the surficial atoms leads to low surface energy. For work function, it is controlled by the surficial atomic species. When a surface contains Li atoms, low work function is expected, which can be attributed to the low electronegativity of Li atom. The (010) T1 surface with Li termination has a minimum work function, 3.40 eV. In addition, as is different from pure metal, work function of some T1 surfaces shows unique behavior under stress state. The (010) T1 surface with Al and Cu termination has an increasing work function under the action of tensile strain. In fact, tensile strain induces the first and second surface layer to merge, which can improve the surface electronic density and raise work function. As a result, the corrosion resistance can be enhanced. Finally, the effect of alloying elements on the precipitation of T1 phase is studied. Al(111)/T1(010) interface is built and the substitution energy of Mg, Zn and Ag are calculated. Comparing with Mg and Zn atom, the energy of Ag atom to substitute the interfacial one is low, meaning that Ag can relax the strain in the interface. Ag atom has the closest atomic radius to Al atom, and the same chemical valence as Li atom. Therefore, Ag atom is more likely to promote the precipitation of T1 phase, which is also in agreement with the experimental result.