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The strip-like grain shape is one of three important factors (the strip-like grain shape, strong crystallographic texture and plate-like T1 precipitate) influencing the mechanical properties of the third-generation Al–Li alloys. However, studies on its effect have seldom been investigated to date. In the present study, an extended crystal plasticity finite element (CPFE) framework considering the strain gradient effect via incorporating the geometrically necessary dislocation (GND) density is constructed to investigate the compressive deformation behavior of studied AA2099 Al–Li alloy with strip-like grain shape. Good consistency with respect to the true stress-strain curve and texture characteristics between experimental and predicted results confirms the validity of constructed CPFE framework, as well as these fitted material parameters. Simulation results show the occurrence of aggregation for GND density not only near grain boundaries but also at grain interiors, which benefits in blocking the motion of the statistically stored dislocation (SSD) and the occurrence of obvious stress concentration in the constructed polycrystalline model. This demonstrates that the strip-like grain shape could exsert a nonnegligible influence on the mechanical response of studied AA2099 Al–Li alloy. Moreover, the difference between the predicted orientation distribution functions (ODFs) and the difference about the evolution of accumulative shear strain in 12 slip modes collectedly confirm that the strip-like grain shape does exert some influence on slip activities of studied AA2099 Al–Li alloy.

In the present study, effects of T1/T2 precipitates on microstructure characteristics and texture evolution of various AA2099 Al–Li alloy (AA2099-A and AA2099-B) samples are systematically investigated by conducting uniaxial compression experiments at room temperature, followed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements as well as crystal plasticity finite element (CPFE) simulation. The heat treatment for AA2099-A sample consists of solution treatment at 540 °C/1 h and artificial aging at 250 °C/1 h followed by water quenching, while the heat treatment for AA2099-B sample includes solution treatment at 540 °C/1 h and artificial aging at 250 °C/24 h followed by water quenching. Experimental results demonstrate that although dynamic recovery (DRV) serves as the major restoration mechanism for both samples, AA2099-A sample with T1 phase possesses obviously higher mechanical response by comparison with AA2099-B sample with T1/T2 phase. This observation shows a strong precipitate hardening effect derived from these dense and large-sized T1 precipitates in AA2099-A sample. Numerical results based on CPFE simulation demonstrate the occurrence of inhomogeneous plastic strain within the constructed grain-based representative volume element (RVE) model during uniaxial compression. Further statistical analysis on the coefficient variant about equivalent plastic strain verifies this issue and demonstrates that plastic strain distributes more homogeneously in AA2099-A sample than in AA2099-B sample. These dense and large-sized T1 precipitates are responsible for this phenomenon and they result in the fast rotation of grain orientation from //ED to //ED during uniaxial compression.

The friction stir processed pure Ti was annealed at 550 °C with various annealing times. Dry sliding wear tests on friction stir processed and as-annealed pure Ti were performed at room temperature. Friction coefficient and wear rate of the alloys were measured. The results showed that the friction stir processed pure Ti with high hardness revealed lower wear resistance than as-annealed samples. The stored energy of the samples before and after annealing treatment were calculated. The relationship between work hardening and wear resistance of pure Ti was discussed. The run-in period increased as the stored energy in the pure Ti decreased. The fine-grained pure Ti with 400 kJ/m3 low angle grain boundaries stored energy exhibited the lowest wear rate. The wear mechanism of fine-grained pure Ti changed from fatigue wear and abrasive wear to adhesive wear after annealing treatment. Keywords: Titanium alloy, Friction stir processing, Annealing, Stored energy, Wear resistance

A Cu-10Fe alloy with magnetron sputtered Al films was irradiated by high current pulsed electron beam (HCPEB) with various pulse numbers, next changes of its microstructure and corrosion property were investigated. Compared with the initial sample, microhardness and corrosion resistance of the aluminized Cu-10Fe alloys after the HCPEB treatment are remarkably improved with increasing pulse numbers. This improvement could be attributed to formation of Al2Cu intermetallic compounds, occurrence of liquid phase separation and grain refinement in the surface layer of the Cu-10Fe alloy during the process of rapid remelting and solidification induced by the HCPEB treatment.

Microstructures of CuCr25 and CuCr50 alloys treated by high current pulsed electron beam (HCPEB) were investigated in this work. The microstructure and solidification behavior of the Cr-rich phases were characterized by scanning electron microscopy (SEM). Results show that a remelting layer of 3~5 μm is formed on the surface of Cu-Cr alloys. The microstructure of the remelting layer reveals that both the fine dispersion of Cr-rich spheroids and the craters appear after HCPEB treatment. This means that metastable liquid phase separation occurs during rapid solidification under HCPEB treatment. In addition, the appearance of relatively large craters in the subsurface of Cr-rich particles with the distance about 5-10 μm provides direct evidences supporting results reported by other researchers in terms of numerical simulation temperature field of HCPEB treatments.