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In this work, 2060 Al-Li alloy was joined by refill friction stir spot welding (RFSSW). The effects of the tool's rotating speed and welding time on the microstructure and mechanical properties of the welded joints were studied. The results showed that joints without defects can be obtained within a wide range of welding parameters. Tiny voids were formed when using a low rotating speed of 1600 rpm, and incomplete refilling was obtained when using a short welding time of 1 s. Increasing the rotating speed from 1600 to 2000 rpm increased the grain size of the stir zone (SZ). When using a short welding time of 1 s, the grains of the SZ were not completely broken with high orientation differences in the grains. Higher hardness was obtained in the SZ when using a lower rotating speed and shorter welding time. Increasing the rotating speed increased the joint strength, while short and long welding times decreased the joint strength. [ABSTRACT FROM AUTHOR]

In this work, 2060 Al-Li alloy was joined by refill friction stir spot welding (RFSSW). The effects of the tool’s rotating speed and welding time on the microstructure and mechanical properties of the welded joints were studied. The results showed that joints without defects can be obtained within a wide range of welding parameters. Tiny voids were formed when using a low rotating speed of 1600 rpm, and incomplete refilling was obtained when using a short welding time of 1 s. Increasing the rotating speed from 1600 to 2000 rpm increased the grain size of the stir zone (SZ). When using a short welding time of 1 s, the grains of the SZ were not completely broken with high orientation differences in the grains. Higher hardness was obtained in the SZ when using a lower rotating speed and shorter welding time. Increasing the rotating speed increased the joint strength, while short and long welding times decreased the joint strength.

To investigqte the ellect ol solute segregation behavior on the microstructure and corrosion behavior ol Al Li alloy during twin roll casting, aluminum lithium alloy casting and rolling slabs under dillerent process ranges were successfully prepared, and a thermal Ilow coupling model was constructed. The dillerences in corrosion resistance ol tissues under dilierent process conditions were investigated by combining field emission Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). The results indicate that there is a significant macroscopic segregation phenomenon in the preparation ol TRC-3 under high casting and rolling speed conditions. The results of this segregation mechanism were analyzed in detail bycombining temperature and Ilow rate calculations. Segregation will be inherited into the linal T6 state organization, worsening the precipitation ol Tx phase and deteriorating the linal corrosion resistance. The mechanism of the influence ol segregation on corrosion behavior was deeply discussed, and a cast rolled aluminum lithium alloy process that can achieve low segregation and high corrosion resistance was proposed. [ABSTRACT FROM AUTHOR]

In a vacuum environment, large and near-net-shaped 2060 Al–Li alloy tubes were fabricated by centrifugal casting for the first time, and a heat-flow simulation model was established to study process parameters and the solidification behavior. The microstructure and mechanical properties of the alloy were investigated. It was found that in the forming range, the texture was gradually dominated by fine and homogeneous equiaxed grains (average grain size = ∼64 μm) with the decrease in pouring temperature, and segregation decreased because solute particles moved in orientation for less time under the physical field. The tensile strength of the T8 state reached 541 MPa under the process parameters of pouring temperature = 680 °C and rotational speed = 900 r/min. With the increase in rotational speed, the filling capacity was improved and shrinkage defects were reduced; thus, the alloy exhibited excellent strength. The tensile strength of the T8 state reached 516 MPa under the process parameters of pouring temperature = 760 °C and rotational speed = 1000 r/min.

• LSP increased the hardness and introduced compressive residual stresses. • LSP can significantly improve the fatigue life of hole structures component. • Better fatigue performance can be obtained by drilling holes after LSP. In this study, laser shock peening (LSP) was used to modify the microstructure and mechanical properties of 2060-T8 aluminum–lithium alloy. The results demonstrated that LSP induces a gradient hardened layer and high amplitude compressive residual stress into the material. Due to the plastic deformation introduced by LSP, more stable and higher density geometrically necessary dislocations were developed around the grain boundaries, which changed the microstress distribution of the hardened layer and produced a more stable strengthening effect of hetero-deformation. The influence of LSP treatment parameters, processing sequence for the LSP treatment, and drilling on the fatigue properties of the alloy was also studied. The fatigue life of samples with holes drilled either before or after LSP were both improved. However, the fatigue life of the samples that were drilled after treatment was much longer than that for samples drilled prior to treatment. For the untreated sample, the crack initiated at the edge of the hole. However, after LSP with different sequences, the fatigue crack initiation location shifted to the most vulnerable position of the sample, such as the central region along the thickness direction or the transition area between LSP-treated and untreated regions. [ABSTRACT FROM AUTHOR]

In this work, the wear behaviors of a 2060 Al-Li alloy prepared by the twin-roll casting (TRC) process was analyzed and supplemented with coupling simulation calculations. As the load increased from 2 N, 5 N, 10 N, and 20 N at room temperature, the friction coefficient decreased due to the oxidation lubrication triggered by heat accumulation, which was calculated via the simulation; the wear volume decreased; and the decrease in wear volume rise rate was a result of dynamic recrystallization and grain rotation. Observing the grain rotation and analyzing the texture evolution law during wear tests with scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD) was an innovation. To support the rotation behavior, a method for calculating the Schmid factor of rotating grains was developed. As the load rose, the R-Cube {001} 〈110〉 texture rotated to the rotating cube {001} 〈310〉 texture towards the α-fiber line. The modification decreased the maximum Schmid factor along the sliding and rolling directions, indicating an increase in initial strength and wear resistance. In addition, at a 2 N load, the TRC-3 sample with higher substructure and deformation texture exhibited less wear volume than the TRC-6 sample.

Al–Li alloy has been widely used in the aerospace field owing to its high strength and low density. In this study, alternating current cold metal transfer (AC CMT) along with a high-frequency pulse current technique was used to weld a 2060 Al–Li alloy using an ER5356 wire. The effect of pulse frequency on the arc shape, microstructure, and mechanical properties of the welded joints was examined, and mechanical performance testing was conducted. The results revealed that the arc diameter, arc length, and arc volume showed a trend of increasing first and then decreasing with an increase in the pulse frequency and reached their peak values when the pulse frequency was 50 kHz. Coupling the welding process with a high-frequency pulse resulted in grain refinement, which was attributed to the stirring action of the arc force. Both the porosity levels and grain size decreased with increasing frequency. When the pulse frequency was 70 kHz, the porosity level was the lowest, and the grain size was refined to 24.1 μm. The tensile strength of the welded joints also increased with the pulse frequency, and a maximum tensile strength of 249 MPa was observed at 70 kHz.

The microstructure characteristic, fatigue damage behaviours and evolution of microstructure during the fatigue testing of 2060 Al-Li alloy thin plate were studied by fatigue tester equipped with in-situ observation device, OM, EBSD, SEM and TEM. The results show that recrystallized grains with irregularity shape and large size are observed, the Goss and Cube texture are the mainly types, abundant of T1 with size of 50~60nm are found in grains. During axial loaded fatigue testing, a crack initiates from the edge of sample and extend into grain along the direction with maximum Schmid factor. When the crack reaches and crosses the first grain boundary, the extending direction deflects from 45° degree to perpendicular with loading direction, and propagates along this direction till the sample quickly fracture. A large size deformation region contains numerous slip strips around the crack tip during the initiation and extending process is observed. The dislocations cut across the T1 precipitates located in grains during deformation, and release the stress concentration on the crack tip. The fatigue crack extends across the grains with serrated shape can result from the big orientation difference of grains and easy screwed T1 precipitates.

Microstructural and mechanical properties of 2.0-mm-thick 2060 Al-Cu-Li alloy joints obtained at different rotation speeds were assessed in this study. The rotation speeds ranged from 400 to 1300 rpm, with welding speed kept at a constant value of 100 mm/min. With the increase in rotation speed, grain coarsening occurred while the density of precipitation decreased in the stir zone (SZ), and great amounts of the Al2CuLi and Al2Cu phases were dissolved while only small amounts of the Al3Zr and Al3Li phases remained. The lowest hardness was found at the interface between the heat-affected zone (HAZ) and thermo-mechanically affected zone (TMAZ); the average hardness value of SZ increased, while the lowest hardness moved in the direction away from the center of joints. The ultimate strength (UTS) of weld first increased rapidly and then slowly decreased as rotation speed increased, with a maximum value of 443 MPa obtained at a rotation speed of 600 rpm, reaching 83.58% of the base metal (BM) strength. Three fracture modes were established to illustrate the growth mechanism of the crack. Analysis of the fracture surface showed that insufficient materials flowed and coarsened secondary phases caused the joint fracture. [ABSTRACT FROM AUTHOR]

Particle-reinforced Metal Matrix Composites (PMMCs) of 2060 Al-Li (aluminium-lithium) were prepared with nano-sized TiC (titanium carbide) particles and investigated the physico-chemical behavior of these nanoparticles using the electron probe microanalyzer (EPMA), differential scanning calorimetry (DSC), electron back-scattered diffraction (EBSD), transmission electron microscope (TEM), and simulations. A model, coupling heat-flow-solute-phase field was established, linking macroscopic and microscopic conditions, which predicts the cooling rate, grain size, discrete phase distribution, and segregation law. The relationship between the TiC nanoparticles and aluminium matrix was evaluated, and (111) TiC was found to be parallel to the (111) Al, with low mismatch and smooth interfacial connections, which, in turn, facilitated efficient nucleation of the aluminium matrix. The grain size of the direct casting samples (DC) is 541.8 μm, and that of the direct casting samples reinforced by nano-particles (TDC) is 41.3 μm, a substantial reduction of 92.4%. Compared to DC, the tensile strength of TDC increased from 516 MPa to 575 MPa, and its elongation increased from 5.6% to 9.9% after T8 treatment. The reinforced nanoparticles were found to be rotation sensitive and reduced the localized large deformation, thus weakening the texture, and reducing the structural anisotropy; the nanoparticles reduced the accumulation of high-concentration solutes in the liquid phase, and also reduced the segregation gradient. The relatively simple preparation process makes it suitable for large-scale industrial production of PMMCs Al-Li alloys. [Display omitted] • Composites of TiC and 2060 Al-Li were prepared, and both the tensile strength and ductility after T8 treatment significantly improved, making it suitable for large-scale industrial production of Al-Li alloys. • The relationship of the interface between TiC and aluminium matrix was observed and analyzed in detail. • A model, coupling heat-flow-solute-phase field was established, that allowed analysis of the segregation behavior under the influence of PMMCs in both simulation and experimental dimensions. • The fine structure of PMMCs had a higher rotational sensitivity during deformation, which made the deformation uniform, weakened the texture, and delayed the development of hard orientation, thus weakening the anisotropy. [ABSTRACT FROM AUTHOR]

The microstructures, mechanical properties and corrosion resistance of 2060 AL-Li alloy subjected to laser shock peening (LSP) with power densities of 3, 4 and 5 GW·cm−2 were investigated comprehensively. Microhardness, residual stress, wear resistance and fatigue life were tested on LSP alloys to analyze the mechanical properties and the corrosion behavior was investigated by electrochemical test. X-ray diffraction (XRD) and field emission transmission electron microscopy (FE-TEM) were used to investigate the surface microstructure evolution. The results show that LSP leads to a high magnitude of surface compressive residual stress and a significant increase of dislocation density near the surface in the plastic deformation layer. Additionally, with the increase of laser power density, the microhardness, compressive residual stress and surface roughness increase, while the friction coefficient and wear rate decrease compared to pristine alloy. The fatigue life of the sample with a laser power density of 4 GW·cm−2 reaches the highest value of 6.00 × 104 times, approximately twice that of the pristine sample (2.98 × 104 times), which is mainly attributed to the surface residual compressive stress, high density dislocations and surface hardening owing to the LSP. The corrosion resistance of the LSP alloys modestly decreases in a 3.5% NaCl solution compared with pristine alloy, which mainly ascribes to the increase of surface roughness. Laser shock peening with a GW cm−2 level power density is employed to form high residual compressive stress and increase the dislocation density near the surface layer of the 2060 Al Li alloy. The LSP alloys with power densities of 4 GW cm−2 achieved the highest fatigue life of 6 × 104 times at a maximum cyclic stress of 330 MPa, which is far higher than that of the pristine alloy. [Display omitted] • Laser shock processing is employed to modify the 2060 Al Li alloy. • The high-density dislocation density is obtained near the surface layer of the 2060 Al Li alloy. • High residual compressive stress is formed on the alloy surface. • The microstructure, friction properties and fatigue life of 2060 Al Li alloy are improved. [ABSTRACT FROM AUTHOR]

• The elevated mechanical properties of high strength of 2060 Al-Li alloy were considerably influenced by LSP. • The variation of microstructure and residual stress along the depth of LSPed 2060 Al-Li alloy were studied by TEM and XRD. • The primary mechanism of LSP for improving high temperature tensile properties was established. ga1 Laser shock peening (LSP) is a promising surface technique effective to improve mechanical properties by laser modification. In this study, LSP was used to strengthen the surface of a new generation of light-weight Al-Li alloy (i.e., 2060 alloy). High-density dislocations were formed in the vicinity of precipitate phase. A residual stress of compressive state was detected on the surface. According to the tensile tests conducted at various temperatures, the strength of the alloy was improved with LSP, but simultaneously, the ductility was reduced. The fractograph on the tensile sample subjected to LSP, or as received (free of the modification by laser), was characterized by a quasi-cleavage when the tensile temperature was below 200 °C, whereas ductile fracture was considered to be a determining factor at the temperature of tension above 300 °C. Dislocation strengthening was analyzed as a primary mechanism of LSP for improving high-temperature tensile properties. Namely, this improvement was attributed to the existence of a lot of dislocations near precipitates. [ABSTRACT FROM AUTHOR]