Recrystallization and texture

The study systematically investigated the impact of asymmetric rolling (AR) and subsequent aging treatment on the microstructure and mechanical properties of Al–Cu–Li–TiC/TiB₂ alloy. The average grain size of the as-cast A0 and A1 alloys was 249.87 μm and 38.2 μm, respectively. The grain size was significantly refined by TiC and TiB₂ particles. The texture of A0 and A1 samples after symmetric rolling (SR) was dominated by the β-fiber, including typical Copper, S, and Brass rolled textures. The core of the board has a relatively high proportion of Brass texture. The grain size of the AR sheet increases gradually from the surface to the center, with the middle to fast (MF) layer having the largest grain size. The middle to slow (MS) layer has the highest strength of Goss texture, indicating that the shear bands formed by AR are mostly located in the MS layer. A significant amount of T₁ precipitate was observed in the aged sample, and a new T₁ phase composite with a thickness of 1.426 nm was found in the AR sample. The structure of the composite consists of two parallel T₁ precipitates with Al–Cu layer atoms at the center. The growth behavior of the composite is such that the new T₁ precipitate adheres to one side of the original T₁ precipitate and grows parallel in the form of T_1P-T₁. In the T85 state, the A0SR samples exhibit a yield strength, tensile strength, and elongation of 503 MPa, 518 MPa, and 7.5%, respectively. The A1-SR samples exhibit a yield strength, tensile strength, and elongation of 520 MPa, 526 MPa, and 8.2%, respectively. The A0-AR samples exhibit a yield strength, tensile strength, and elongation of 553 MPa, 572 MPa, and 4.5%, respectively, while the A1-AR samples exhibit a yield strength, tensile strength, and elongation of 580 MPa, 605 MPa, and 5.2%, respectively. The increase in yield strength can be attributed to fine-grained strengthening, precipitation strengthening, and Orowan strengthening brought about by nano TiC/TiB₂ particles.

Face-centered cubic (FCC) metals were subjected to heavy rolling and two-step recrystallization annealing to form sharp cubic textures. The traditional theory states that the formation of recrystallized cubic-oriented grains originates from rolling cube grains. However, in our study, the Ni8W alloy underwent severe deformation during rolling, forming a typical brass-type rolling texture with almost no cubic-oriented grains. The quasi-3D electron backscatter diffraction results indicated that the newly generated cubic grains were not necessarily adjacent to the rolling cubic grains. Instead of growing from excited rolling cube grains, we found newly oriented recrystallized cubic grains generated from twin growth. Initially, most recrystallized grains undergo grain boundary migration or merging during low-temperature recrystallization annealing. Under such conditions, the initial recrystallized grains maintained the same orientation as the original matrix. However, it is also possible that the initially newly oriented recrystallized grains were generated through twinning. The {221}<122> orientation grains can cause cubic orientation by Σ3 boundaries. This twinning process reveals another pathway for generating initially recrystallized cubic grains in highly deformed FCC alloys. The recrystallized cubic-oriented grains ultimately evolved into cubic textures owing to their growth advantages, as described by the traditional theory. This discovery solves the puzzle of the recrystallization nucleation mechanism for cubic-oriented grains. It can help us better understand the evolution of the recrystallized cubic texture in heavily deformed FCC alloys.

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 Cube_ND nuclei, and P-oriented grains dominated. Thus, the A0 alloy sheet was dominated by Cube_ND 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.

Medium to high stacking-fault energy FCC metals develop a pronounced cube texture during static recrystallization. Previous studies reported that the recrystallized grains can nucleate from the cube-oriented regions developed in the non-cube grains during plane strain compression. However, the mechanisms behind the development of cube orientation in the non-cube grains are still unknown. In this work, we used an elasto-viscoplastic fast Fourier transform (EVP-FFT) based crystal plasticity model to study the lattice rotation of non-cube orientations under plane strain compression. Firstly, we focus on a non-cube grain which developed the cube orientation in previous experimental work. The non-cube orientation does not rotate towards the cube orientation during single material point deformation under ideal plane strain compression. In contrast, the same non-cube orientation develops cube-oriented fragments during the polycrystalline deformation. Analysis of the micro-mechanical fields reveal that the local deviation of the RD-ND shear component leads to a remarkable change in the slip system activity which promotes the lattice rotation towards the cube orientation. Although the mechanism remains unchanged, the location and volume fraction of the cube orientation developed in the non-cube grain vary significantly in different grain neighborhoods. For the general case of a polycrystalline microstructure, deviation of the RD-ND shear component shows the highest correlation with the development of the cube orientation in the non-cube grains. The deviation is larger for the non-cube grains with higher Taylor factor. These findings have significant implications for the cube texture control during the practical rolling operation and recrystallization.

A simultaneous prediction of macroscopic deformation and microstructure evolution is critical for understanding the deformation mechanism of components. In this work, the hydro-bulging process of 2219 aluminum alloy sheet was investigated using cross-scale numerical modeling, in which the macroscopic finite element method (FEM) and crystal plasticity finite element method (CPFEM) were combined. The calculated texture evolution exhibits good agreement with the experimental results, and the stress error between the two scales is generally small. The effects of different strain states on texture evolution and slip mode are further discussed. As the strain ratio η increases, the volume fractions of the initial Rotated Copper texture component and γ-Fiber texture component decrease significantly, which tend to be stabilized at P texture component. The initial Rotated Cube texture component is inclined to rotate towards the Cube texture component, while the volume fraction of this orientation is relatively stable. The lower strain ratio can considerably enhance the activity of more equivalent slip systems, promoting a more uniform strain distribution over grains. The difficulty of grain deformation changes as the lattice rotates. The grain with easy-to-deform orientation can gradually rotate to a stable orientation during plastic deformation, which has a lower Schmid factor.

In this study, particle-reinforced aluminum matrix composites (PRAMCs) of 2055 Al–Cu–Li alloy were prepared with nano-sized TiB₂+TiC particles, and electron probe microanalyzer (EPMA), differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to investigate the recrystallization and aging behavior of 2055 + TiB₂+TiC alloy. The relationship between TiB₂+TiC nanoparticles and the T₁ strengthening phase during aging was investigated, and the promotion effect of nanoparticles on the T₁ phase during aging was explained by the stored energy and mismatch in the coefficient of thermal expansion (CTE). The grain size of as-cast 2055, 0.5, and 1.0 alloys were 112 μm, 87 μm, and 68 μm, respectively. The TiB₂+TiC nanoparticles were found to hinder the development of α-Al dendrites in solidification and refine the grains. The recrystallization behavior during solid solution treatment was mainly a particle stimulated nucleation (PSN) mechanism, and TiB₂+TiC nanoparticles enhanced the recrystallization resistance. The number density of T₁ phase in the pre-deformed 2055 + TiB₂+TiC alloy was 452 ± 12/μm⁻² with an average size of 73 ± 3 nm, which was finer than 2055 alloy, resulting from the retention of more dislocations or CTE effects at the TiB₂ or TiC interface in the deformed 0.5 or 1.0 alloy. These factors cause Cu atoms to aggregate and provide favorable conditions for T₁ phase precipitation. Compared with 2055, the ultimate tensile strength of the 0.5 sample was increased from 424 MPa to 455 MPa under condition A and from 498 MPa to 550 MPa after pre-deformation. This study can be used as a reference for improving the mechanical properties of Al–Li alloys.