GP Zones Research Articles

Study on the solid solution temperature of achieving ultra-high strength in wire-arc additive manufactured Al-Zn-Mg-Cu aluminum alloy

Al-Zn-Mg-Cu aluminum alloys are typically heat-treatable aluminum alloys. The heat treatment has a significant effect on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy. In this study, the solid solution temperature of achieving ultra-high strength in wire-arc additive manufactured 7B55 aluminum alloy was systematically investigated. The results showed that the microstructure of the as-deposited 7B55 aluminum alloy was composed of equiaxed grains with an average grain size of 4.2 ± 0.5 μm. A large number of the second phases were continuously distributed along grain boundaries. The precipitated phases within grains were mainly composed of the larger η phases and the smaller η′ phases, and the amount of precipitated phases was fewer. The second phases distributed along grain boundaries gradually dissolved into α-Al matrix with the increase of solid solution temperature, resulting in a higher supersaturation of the α-Al matrix and more homogeneous distribution of alloy elements. Combined with the results of DSC analysis, the optimal solid solution temperature of the 7B55 aluminum alloy was determined to be 480 °C. After solid solution of 480 °C，the microstructure was still composed of equiaxed grains with an average grain size of 4.8 ± 0.4 μm. The size of the grain did not grow significantly. A larger number of nanoscale fine GP zones, η′ phases and secondary Al3(Sc,Zr) particles were precipitated within the grains during subsequently artificial aging process, resulting in a significant increase in tensile properties. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) reached 621 MPa, 555 MPa and 5.73%, respectively, which was significantly higher than the strength level of WAAM aluminum alloy reported among all the existing literature.

On the low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing

The low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing (NIA) was examined at different strain amplitudes. We showed that NIA improved the low cycle fatigue life (more than 7000 cycles) by optimising the precipitate configuration within 5.5 h while maintaining comparable mechanical properties (570 MPa for tensile strength) and conductivity (nearly 39% IACS) to conventional isothermal ageing, simultaneously. Experimental observation combined with molecular dynamic simulation revealed that precipitation configuration manipulated by NIA had a crucial effect on fatigue resistance. A great number of repeatedly sheared and locally destructed GP zones enhanced co-planar slip and slip localisation in the under-aged alloy during the early stage of NIA, responsible for the dramatic displacement steps on the surface and resultant poor fatigue performance. As the NIA further proceeded, moderately coarsened precipitates with an average dimension of 6.0 nm and elevated number density effectively impeded the dislocation movement and weaken the slip localisation to a great extent, improving the fatigue performance within a few hours.

Achieving high strength in selective laser melting AlSi10Mg alloy by adding microsized pure Cu particles

In this work, a high-strength Al–Cu–Mg–Si alloy was prepared by a selective laser melting (SLM) process with blended powders consisting of AlSi10Mg and microsized pure Cu powders. The influence of Cu addition on the microstructure and mechanical properties of AlSi10Mg alloy has been systematically investigated. The Al–Cu–Mg–Si alloy has a hardness of 173 HV, an ultimate tensile strength of 732 MPa, and a yield strength of 389 MPa, reaching the level of high-strength aluminum alloys. Such increase in the strength and hardness can be attributed to the refinement of eutectic network, enhanced solid solution strengthening and elimination of fracture-prone heat affected zone (HAZ). In addition, the formation of the GP zone caused by adding Cu promotes the precipitation of Si particles within the eutectic network, and Si particles, as the non-shear deformed second-phase, can significantly increase the Orowan strengthening effect. After aging at 180 °C for 2 h, the hardness and yield strength of the alloy are increased to 183 HV and 522 MPa respectively. The presence of the θ′-Al2Cu phase and the high-density of Si particles after 2 h of peak aging further increases the strength and hardness of the alloy.

Discovery of Guinier-Preston zone hardening in refractory nitride ceramics

Traditional age hardening mechanisms in refractory ceramics consist of precipitation of fine particles. These processes are vital for widespread wear-resistant coating applications. Here, we report novel Guinier-Preston zone hardening, previously only known to operate in soft light-metal alloys, taking place in refractory ceramics like multicomponent nitrides. The added superhardening, discovered in thin films of Ti-Al-W-N upon high temperature annealing, comes from the formation of atomic-plane-thick W disks populating {111} planes of the cubic matrix, as observed by atomically resolved high resolution scanning transmission electron microscopy and corroborated by ab initio calculations and molecular dynamics simulations. Guinier-Preston zone hardening concurrent with spinodal decomposition is projected to exist in a range of other ceramic solid solutions and thus provides a new approach for the development of advanced materials with outstanding mechanical properties and higher operational temperature range for the future demanding applications.

Study of microstructure evolution of friction stir welded novel (Al-Zn-Mg)-Fe (HE700) cast alloys for automotive applications

Light weighting of automobiles would improve fuel efficiency and reduce emissions. Newly developed high-strength, high-elongation (Al-Zn-Mg)-Fe alloys for structural shape casting applications have the potential to fulfill the demand for significant lightweighting of components. Joining such shape casting alloys to form a high integrity component assembly is a critical process in structural lightweighting. Friction stir welding has recently emerged as an effective joining method for aluminium alloys. In this work, friction stir welding was used to join these new-generation (Al-Zn-Mg)-Fe cast alloys. The critical process parameters such as rotation and traverse speed were optimized through a detailed microstructural study and mechanical property evaluation of the welds. Three different tool rotation speeds (600, 800, and 1000 rpm) and traverse speeds (25, 50, and 75 mm/min) were the independent parameters. The welds made with 800 rpm and 25 mm/min traverse speed showed the best properties with no weld/microstructural defects. Friction stir welding also refined the microstructure and uniformly distributed the agglomerated Al-Fe-based intermetallic particles. The microhardness and tensile properties (longitudinal direction) of the stir zone increased significantly (Ultimate tensile strength = 380 MPa, Yield strength = 250 MPa) with appreciable ductility (31%) due to the microstructural refinement despite the dissolution of the strengthening precipitates such as Guinier-Preston zones and ηꞌ phases. The study was able to establish a viable window of processing parameters for joining the new generation Al-Zn-Mg-Fe alloys for structural lightweight components.

Predicting the early stages of solid-state precipitation in Al-rich Al-Pt alloys

The high strength of structural aluminium alloys depends strongly on the controlled precipitation of specific intermetallic phases, whose identity and crystal structure can be difficult to predict. Here, we investigate the Al-Pt system, which shows some similarity to the Al-Cu system as one of the main intermetallic phases, Al2Pt, is nearly isostructural with θ′ (Al2Cu), the metastable phase responsible for the high-strength of Al-Cu alloys. Using a combination of density-functional theory (DFT) calculations and classical nucleation theory (CNT) applied to the Al-Pt system, we design a workflow to predict the thermodynamics of solid solution, intermediate phases such as GP zones, stable and metastable precipitates, and their precipitation sequence. This workflow can be applied to an arbitrary binary alloying system. We confirm the known stable phases Al4Pt, Al21Pt8, Al2Pt, Al3Pt2, AlPt (α&β), Al3Pt5, AlPt2 (α&β) and AlPt3 (α&β). We also reveal the possible existence of two phases of chemical formulae Al5Pt and Al3Pt. This large number of intermetallic phases is due to the strong bonding between Al and Pt, which also leads to a significantly favourable Pt solute formation energy in the Al matrix. Our findings are compared with the known precipitation characteristics of the binary Al-Cu and Al-Au systems. We find that the θ′-like Al2Pt precipitate phase has a lower coherent interfacial energy than θ′. Our calculations strongly suggest that Al2Pt will precipitate first in Al-rich Al-Pt alloys and will form bulk-like interfaces similar to η (Al2Au) rather than like θ′ (Al2Cu).

Investigation of Pre-Aged Hardening Single-Point Incremental Forming Process and Mechanical Properties of AA6061 Aluminum Alloy.

Currently, the single-point incremental forming process often faces issues such as insufficient formability of the sheet metal and low strength of the formed parts. To address this problem, this study proposes a pre-aged hardening single-point incremental forming (PH-SPIF) process that offers several notable benefits, including shortened procedures, reduced energy consumption, and increased sheet forming limits while maintaining high mechanical properties and geometric accuracy in formed components. To investigate forming limits, an Al-Mg-Si alloy was used to form different wall angles during the PH-SPIF process. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) analyses were conducted to characterize microstructure evolution during the PH-SPIF process. The results demonstrate that the PH-SPIF process can achieve a forming limit angle of up to 62°, with excellent geometric accuracy, and hardened component hardness reaching up to 128.5 HV, surpassing the strength of the AA6061-T6 alloy. The DSC and TEM analyses reveal numerous pre-existing thermostable GP zones in the pre-aged hardening alloys, which undergo transformation into dispersed β" phases during the forming procedure, leading to the entanglement of numerous dislocations. The dual effects of phase transformation and plastic deformation during the PH-SPIF process significantly contribute to the desirable mechanical properties of the formed components.

On the role of Ag additions on the initial solute hardening and competitive precipitation of Al-Cu-Mg alloys

The initial solute clustering is known to significantly affect the subsequent precipitation of various strengthening precipitates that determine the mechanical properties of Al-Cu-Mg-Ag alloys. In this work, the influence of Ag variations on the initial cluster hardening and microstructure evolution of Al-Cu-Mg-Ag alloys is investigated by quantitative transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and atom probe tomography (APT) analysis. Our statistical data and calculation results indicate that the overwhelming Mg-Ag co-clustering by increasing Ag from 0.41 to 0.97 indeed enables a higher nucleation rate of Ω phase and contributes to a denser Ω precipitation generating a stronger age-hardening response at 180 ℃. Analysis of the contribution of individual precipitates to the yield strength highlights the positive role of increasing Ag on improving the cluster hardening capacity of Mg-Ag co-clusters by increasing its order hardening level. Compared with Cu-Mg co-clusters and GP zones, Mg-Ag co-clusters exhibit a greatest strengthening contribution to yield strength of the material as the bulk Ag content increases. Except for GP zones, Mg-Ag and Cu-Mg co-clusters prefer to exhibit a strong order hardening rather than modulus hardening in initially aged alloys. In addition, the average grain sizes, as well as the proportions of low angle grain boundaries (LAGBs) and high angle grain boundaries (HAGBs), reveal no distinct differences in both alloys, suggesting the independence of grain structure on the bulk Ag content.

A corrosion-resistant and age-hardenable Mg-Al-Mn-Ca-Ce dilute alloy with fine-grained structure processed by controlled rolling

Low strength and poor corrosion resistance are two long-standing bottlenecks with dilute Mg alloys. Here, we report that the corrosion resistance of Mg-0.6Al-0.5Mn-0.2Ca (wt.%) alloy sheet can be significantly improved by micro-alloying with 0.3 wt.% Ce, and the strength can be considerably augmented after aging treatment. Simultaneous optimization of strength, ductility, and corrosion resistance is difficult due to the inherent trade-off in Mg alloys. Surprisingly, our aged Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy features with yield strength (YS) of ∼194 MPa, ultimate tensile strength (UTS) of ∼265 MPa, elongation to failure (EF) of ∼17.2%, and corrosion rate (CR) of 2.2 mm y−1, the combination of which exhibits competitive advantage over other comparative dilute Mg alloys. It is found that Ce addition decreases the activity of cathodic phases, inhibits detrimental effects of Fe impurities, and forms a protective Ce-containing surface film. The high strength stems from the precipitation of ordered Guinier-Preston (G.P.) zones dispersed in uniform fine grains with an average grain size of ∼8.2 μm. The atomic-scale G.P. zones result in a noticeable age hardening response but do not act as crack initiation and propagation site, so our alloy also performs satisfactory ductility. This work sheds light on the design and fabrication of strong, ductile, and corrosion-resistant dilute magnesium alloys to be used in electronic products and automotive bodies.

First-Principles Study on Structure and Stability of GP Zones in Al-Mg-Si(-Cu) Alloy.

Nanostructured Guinier-Preston (GP) zones are critical for the strength of Al-Mg-Si(-Cu) aluminum alloys. However, there are controversial reports about the structure and growth mechanism of GP zones. In this study, we construct several atomic configurations of GP zones according to the previous research. Then first-principles calculations based on density functional theory were used to investigate the relatively stable atomic structure and GP-zones growth mechanism. The results show that on the (100) plane, GP zones consist of {MgSi} atomic layers without Al atoms, and the size tends to grow up to 2 nm. Along the (100) growth direction, even numbers of {MgSi} atomic layers are more energetically favorable and there exist Al atomic layers to relieve the lattice strain. {MgSi}2Al4 is the most energetically favorable GP-zones configuration, and the substitution sequence of Cu atoms in {MgSi}2Al4 during the aging process is Al → Si → Mg. The growth of GP zones is accompanied by the increase in Mg and Si solute atoms and the decrease in Al atoms. Point defects, such as Cu atoms and vacancies, exhibit different occupation tendencies in GP zones: Cu atoms tend to segregate in the Al layer near the GP zones, while vacancies tend to be captured by the GP zones.

Enhanced intragranular dislocation capture ability in nano/ultrafine Al-Zn-Mg-Cu alloy by burnishing-assisted two-stage aging treatment-induced dynamic nucleation

The effects of burnishing-assisted two-stage aging (BATSA), including pre-aging, burnishing, and subsequent aging (SA) on the microstructural evolution, precipitation, and hardening behavior of Al-Zn-Mg-Cu alloy were systematically investigated. Transmission electron microscopy, X-ray diffraction, small-angle X-ray scattering, and Vickers microhardness tests were used to analyze the above-mentioned characteristics of the burnished-layer alloys and the matrix-layer alloys, respectively. The BATSA treatment promotes a concentrated distribution of precipitate sizes, delaying phase coalescence and maintaining a relatively dispersed precipitate distribution. Moreover, the persistent nucleation of Guinier-Preston (GP) zones in burnished alloys was observed during SA. These results are conducive to the enhancement of the dislocation storage capacity of nano/ultra fine-grained alloys (the decrease in dislocation density of pre-aged burnished alloy was about 65% that of non-pre-aged burnished alloy). Based on this, dynamic nucleation induced by pre-aging and burnishing resulted in a better synergy of multiple strengthening mechanisms, significantly shortening the time to peak hardness in pre-aged burnished alloys to about 1/3 that in non-pre-aged matrix alloys, and maintaining hardness stability. Moreover, it was found that the critical width of the in situ phase transformation from GPII zone to η' precipitate can be as low as 3–4 at. planes.

Regulation of precipitation behavior among T1, S', and θ' phases in Al–Cu–Li-(Mg–Ag) alloys by optimizing Ag/Mg ratios

In third-generation Al–Cu–Li alloys, T1, S', and θ' precipitates are the primary strengthening phases, and the strength-ductility synergy of the alloys depends strongly on their precipitation behavior. This study aimed to regulate the precipitation behavior among these precipitates by optimizing Ag/Mg ratio in Al–Cu–Li alloys, and its influence on mechanical properties and fracture mechanism was investigated. To this end, four alloys were designed with a total content of 1.1 wt% of Ag and Mg, and an Ag/Mg ratio ranging from 0.24 to 5.63. The results shows that an increase in the Ag/Mg ratio dramatically accelerated the ageing process and shortened the peak-ageing time. At 150 °C, the precipitation sequence of alloys with an Ag/Mg ratio below 0.95 was SSS→GPB zone +δ′/β'→S'+T1, which transformed into SSS→GP zone +δ′/β'→θ'+T1 when the Ag/Mg ratio was above 1.87. The T1, S', and θ' precipitates coexisted and were dispersedly distributed among studied alloys with an Ag/Mg ratio ranging from 0.95 to 1.87. An Ag/Mg ratio of 1.87 resulted in the fastest ageing hardening response and the highest strength (YS = 705 MPa, UTS = 717 MPa) because of the highest volume fraction of T1 precipitates. Moreover, the fracture mode changed from transgranular fracture to intergranular fracture with increasing Ag/Mg ratio due to the difference in distribution and number density of these precipitates between the matrix and grain boundary.

Designing structures with combined gradient of potential and precipitation in multi-layered aluminum sheet for simultaneous improvement of mechanical properties and corrosion resistance

The effects of an interlayer on the corrosion resistance and mechanical properties of multi-layered aluminum sheets were studied. The interlayer prevents Si diffusion to the core layer and optimizes the potential gradient from the Zn-containing interlayer to the core layer. The presence of the interlayer changes the corrosion mode from pitting and intergranular corrosion (IGC) to exfoliation corrosion. Additionally, the natural aging process forms Guinier-Preston (GP) zones in the core layer, which improves the material's yield strength. First principle calculations show that there is minimal corrosion between the GP zones and Al matrix. Thus, the mechanical properties and corrosion resistance of multi-layered aluminum sheets are improved simultaneously.

Improved creep aging response in Al-Cu alloy by applying pre-aging before pre-straining

The improvement of post-form properties without compromising creep formability has been a critical issue in creep age forming of aluminum alloy component. A pretreatment process incorporating artificial pre-aging at 165 °C for 6 h/12 h/24 h followed by pre-strain (3%–9%) has been developed. This method not only evidently improves the strength but also accelerates the creep deformation during creep aging of an Al-Cu alloy. A strength increase of 50 MPa with a slight decrease of ductility relative to the 9% pre-strained alloy is acquired in the alloy artificially pre-aged for 24 h regardless of the pre-strain level (3%–9%). Artificial aging for 24 h prior to 3% pre-strain enables an increase of creep strain by 30%. The creep strain in the alloy artificially pre-aged for 24 h and pre-strained by 6% is comparable to that in the alloy pre-strained by 9%. The strength and ductility in the alloy artificially pre-aged for 6 h/12 h and pre-strained by 3% are even slightly higher than those in the alloy purely pre-strained by 9%. The characterizations by transmission electron microscopy reveal that pre-aging at 165 °C could promote the accumulation of dislocations during pre-straining due to the pinning effect of pre-existing Guinier-Preston zones (GP zones)/θ″ phases and thus expedite the creep deformation in respect to the pure pre-straining treatment. The enhanced precipitation of θ′ phases at these pinned dislocations contributes to the improved strength after creep aging. The results demonstrate applying artificial pre-aging before pre-straining is an efficient strategy to elevate the creep aging response in Al alloys.

Thermal stability of nanocrystalline surface layer in an aged Al–Zn–Mg–Cu alloy induced by ultrasonic surface rolling processing

This paper investigates the thermal stability of nanocrystalline surface layer in an aged Al–Zn–Mg–Cu alloy fabricated by ultrasonic surface rolling process (USRP). The microstructure of the nanocrystalline surface layer and the microstructure changes of grains and precipitates in the nanocrystalline surface layer after annealing at various temperatures were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The microhardness after annealing was also analyzed. The results show that a nanostructured lamella with a thickness of about 40 nm was prepared in the surface layer of the aged Al–Zn–Mg–Cu alloy after USRP. The granulation of the nanostructured lamellae occurs during subsequent annealing due to recovery and becomes more significant with the increase of annealing temperature. Besides, the coarsening η phases occur at the lamellae boundaries by heterogeneous nucleation. Meanwhile, the precipitate inside lamellae gradually changes from GP zone and η' phase to η phase. The thermal stability of the nanostructured lamellae is excellent below 160 °C, but it deteriorates significantly when the temperature exceeds 200 °C. The hardness variation of the nanostructured lamellae is mainly determined by the variation of lamellae thickness and the precipitation behavior plays an auxiliary role.

Why rolled Mg-Al-Ca-Mn alloys are less responsive to aging as compared to the extruded

Dilute Mg-Al-Ca-Mn alloys exhibit excellent strength-ductility combinations in the peak-aged condition due to ordered, single atomic layer Guinier-Preston (GP) zones. The present work explains why rolled sheet material is softer and less responsive to aging, as compared to extruded. Using crystal-plasticity modeling, it is shown that the initial texture of the rolled material permits the soft modes, basal slip and twinning, to accommodate more of the strain during in-plane tension, and they are less responsive to hardening by the finely dispersed GP zones. Even with the same number density of GP zones, the extruded material is stronger in tension along the extrusion axis due to an initial texture which forces higher relative activity of prismatic slip, a mode previously shown to be strongly affected by the GP zones. The present work reemphasizes the significant role of the initial texture in determining the strength and anisotropy of non-cubic metals and alloys.

Simultaneously improving tensile properties and stress corrosion cracking resistance of 7075-T6 aluminum alloy by USRP treatment

The effect of gradient nanostructure prepared by ultrasonic surface rolling on stress corrosion behavior of 7075-T6 aluminum alloy was studied. Results showed that gradient structure improved stress corrosion cracking (SCC) resistance-strength-ductility synergy. Grain refinement and dislocation proliferation offset strength reduction caused by the dissolution of precipitated phase. The superior SCC resistance was attributed to the reduction of surface roughness and the introduction of compressive residual stress. In addition, grain refinement, re-precipitation of coarse η phase at trigonal grain boundaries and the transformation of intracrystalline precipitated phase from GP zone to η' phase further enhanced SCC resistance.

Characterization of Solid-Solution and Aging Process in Mg-5 wt.%Sn Alloy

Firstly, the properties and the microstructure evolution of the solid-solution process of Mg-5 wt.%Sn were studied. From the motion analysis of resistivity and microhardness during solution treatment, the reasonable solution technology of Mg-5 wt.%Sn should be 12–16 h at 480 °C. After solution treatment at 480 °C for 16 h, the precipitating behavior in supersaturated solid solution. Mg-5 wt.%Sn alloy was investigated. In the aging process, it was observed that there were precipitated phases in the both grain and grain boundaries, and continuous inhomogeneous precipitation occurred along the grain boundaries, and continuous homogeneous precipitation happened in the grain. Transmission Electron Microscope (TEM) analysis indicated the plate- and lath-shaped precipitates within the grains and only the plate-shaped precipitates along the grain boundary. High-Resolution Electron Microscopy (HRTEM) studies have shown that metastable precipitates may occur during aging, coherently or semi-coherent with the matrix. Energy Dispersive Analysis by X-ray (EDAX) analysis showed that the Mg/Sn ratio was not actually constant, and the Sn content of the metastable phase was lower than that of the Mg2Sn equilibrium phase. X-ray diffraction (XRD) studies confirm the existence of this metastable phase, which is supposed to be GP zone and metastable Mg3Sn phase.

Co-strengthening of the multi-phase precipitation in high-strength and toughness cast Al–Cu–Zn–Mg alloy via changing Zn/Mg ratios

The effects of the Zn/Mg ratio on the as-cast microstructure, aging-precipitation behavior, and mechanical properties of cast Al–Cu–Zn–Mg alloys, an interesting precipitation-hardened Al alloy different from the 2XXX and 7XXX, were investigated. The primary phase of the as-cast alloy changed from lamellar θ and S phases to a block S phase with an increased Zn/Mg ratio. The number density of the solely S phases in the peak-aged alloy increased with the Zn/Mg ratio from 0.4 to 1.5, because the Zn promoted the formation of GPB zones. At a Zn/Mg ratio of 2.5, the major precipitates are the S, η, and T phases, due to the preferential interaction of Mg atoms with Zn, which promotes the formation of Mg–Zn clusters and GP zones in the initial stages of aging. The yield strength, ultimate tensile strength, and elongation reached maximum values of 372 MPa, 502 MPa, and 12.3%, respectively. This illustrates the cooperative strengthening of the S, T, and η phases, which pin the moving dislocations and inhibit crack initiation and propagation. A large amount of the T phase in the high Mg content alloy suppresses the formation of the S phase. This multi-phase precipitation addressed the “strength ductility trade-off” in cast Al alloys.

Improved strength and ductility of rapidly solidified 2195 alloy by pre-rolling combined with double aging and interrupted aging

Pre-rolling combined with double aging (DAT8) and interrupted aging (IAT8) were carried out to improve the mechanical properties of rapidly solidified 2195 Al–Cu–Li alloy. For the DAT8 treatment (4% pre-rolling + 120 °C/12 h + 165 °C/16 h), low aging temperature (120 °C) in the first stage forms abundant δ′ phase, which grows into well-dispersed T1 plates in the second stage (165 °C). The IAT8 treatment (165 °C/2 h + 4% pre-rolling + 65 °C/5 day + 165 °C/16 h) first produces some small GP zones, which are connected to dislocations generated by pre-rolling. Subsequent long-term low-temperature aging (65 °C/5d) results in the enrichment of Cu, Mg, Ag and Li atoms on dislocations, significantly enhancing the precipitation driving force of the T1 phase. The results show that DAT8 and IAT8 treatments simultaneously improve the strength and ductility of the alloy. The increased strength is mainly due to the dense precipitation of the T1 phase, generating higher precipitation strengthening, as well as the introduction of high dislocation density, yielding strain strengthening. The improved ductility is attributed to the fine and well-dispersed T1 phase, decreasing the incongruous deformation between precipitates and matrix, and suppressing the formation of precipitation free zone (PFZ), weakening local stress concentration at sub-grain boundaries.