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The evolution of microstructure, texture, and mechanical properties of AZ31 (Mg-3Al-1Zn, wt.%) and Mg-0.6Gd (wt.%) alloys was investigated and compared after high-pressure torsion at room temperature through the equivalent strain range of εeq = 0.6 − 287.5. The results demonstrated that the grain refinement behavior is different for these two alloys. For the AZ31 alloy, dynamic recrystallization (DRX) was restricted leading to a gradual and continuous formation of ultrafine grains with a mean grain size of ~ 0.3 µm through the entire strain range and the development of deviated B, C1, and C2 texture fibers. For the Mg-0.6Gd alloy, the DRX was very fast and a rapid ultrafine grain microstructure with a mean grain size of ~ 0.7 µm was developed at a strain range of εeq = 0.6 − 5.7 and this remained stable with a relatively stable B-fiber over the strain range εeq = 5.7 − 287.5. The evolution of microhardness in the AZ31 alloy indicated a strain hardening without recovery while that of the Mg-0.6Gd alloy showed a strain hardening with recovery. The differences between the AZ31 and Mg-0.6Gd alloys are discussed based on a comprehensive characterization of twinning, dislocation density, the initial microstructure and the presence of second phases. [ABSTRACT FROM AUTHOR]

The evolutions of microstructure and texture and the corrosion behaviour of low light rare-earth containing Mg-1.4Nd and low heavy rare-earth containing Mg-0.6Gd and Mg-0.4Dy (wt.%) were evaluated and compared after processing by high-pressure torsion (HPT) and isochronal annealing at 250 and 450 °C for 1 h using electron backscatter diffraction (EBSD) and electrochemical tests in a 3.5% (wt.%) NaCl solution. The EBSD results show that dynamic recrystallisation (DRX) was restricted in the Mg-1.4Nd alloy which led to a heterogenous deformation microstructure whereas the Mg-0.6Gd and Mg-0.4Dy alloys exhibited a homogenous deformation microstructure formed mostly of equiaxed dynamically recrystallised DRX grains. The HPT processing caused the development of a deviated basal texture in the three alloys. A good thermal stability of the three alloys was noticed after annealing at 250 °C. By contrast, annealing at 450 °C led to a homogenous equiaxed microstructure and weakening of texture for the Mg-1.4Nd alloy and a heterogenous bimodal microstructure with a stable basal texture for the Mg-0.6Gd and Mg-0.4Dy alloys. The HPT-processed Mg–RE alloys exhibited an improved corrosion resistance due to grain refinement. Thereafter, the corrosion resistance of the Mg-0.6Gd and Mg-0.4Dy alloys decreased with increasing annealing temperature due to an increase in grain size while the corrosion resistance of the Mg-1.4Nd alloy was improved after annealing at 450 °C due to precipitation and texture weakening. [ABSTRACT FROM AUTHOR]

The evolution of microstructure and texture during friction stir lap welding (FSLW) of TIMETAL 21S (β-type Ti-15Mo-3Nb-3Al-0.2Si, wt%) sheets were investigated through electron backscatter diffraction (EBSD). Excellent grain refinement is obtained through stir zone (SZ) thickness (1.2–1.8 μm). The microstructure of the thermomechanically affected zone (TMAZ) is characterized by elongated deformed grains surrounded by small recrystallized grains indicating the occurrence of discontinuous dynamic recrystallization (DDRX). The microstructure of heat affected zone (HAZ) is quite similar to the base metal (BM). The texture transformed from weak rolling-recrystallization texture in BM and HAZ to a typical shear texture with the domination of D 1 or D 2 components in the SZ and TMAZ area. A net shear texture gradient is formed across the SZ thickness which is connected with the heterogeneity of deformation. It is believed that the concomitant occurrence of grain size, dislocation and texture strengthening is responsible for the mechanical property distribution in different parts of FSLW joint. • TIMETAL 21S sheets were successfully fabricated by FSLW. • Excellent grain refinement (1.2–1.8 μm) was obtained in SZ during the FSLW. • A net shear texture gradient is developed across the thickness of SZ. • The microstructure evolution of TMAZ indicates the occurrence of DDRX. • The microstructure and texture of HAZ are quite similar to those of BM. [ABSTRACT FROM AUTHOR]

The corrosion behavior of a commercial Al-6061 alloy was explored in a 3.5 % (wt%) NaCl solution after high-pressure torsion (HPT) processing at room temperature for numbers of revolutions of N = 0, 1/2, 2 and 10 turns. The microstructures revealed by electron backscatter diffraction (EBSD) showed excellent grain refinement from 121 ± 5 to 0.44 ± 0.1 μm after N = 10 turns with a high fraction of high-angle grain boundaries (∼65 %). The results from electrochemical tests demonstrate that HPT processing significantly improves the corrosion resistance and reduces the corrosion rate due to a combination of grain refinement, an increased dislocation density and texture weakening. The corrosion mechanism was not affected by the HPT processing and found to be controlled by charge transfer. The corrosion morphology of the HPT-processed sample taken through N = 10 turns and observed after 14 days of immersion showed a smooth surface except for the presence of some corrosion microcracks around large particles enriched with Zn and Fe elements. • Al-6061 alloy was processed by HPT at RT for N = 0, 1/2, 2 and 10 turns. • HPT processing improves the corrosion resistance in 3.5 NaCl solution. • The corrosion mechanism was not affected by the HPT processing. • Grain refinement, dislocation and weak texture contribute to corrosion improvement. [ABSTRACT FROM AUTHOR]

A commercial Al-6061 alloy was processed by high-pressure torsion at room temperature over equivalent strains in the range of ε eq = 0–205 and the evolutions of the microstructure, texture and mechanical properties were investigated using electron backscatter diffraction and Vickers microhardness measurements. The mean grain size decreased significantly from ∼121 ± 5 μm in the initial state to ∼0.45 ± 0.15 μm after a strain of ε eq = 205 and this grain refinement occurred in three distinct stages. First, the grain size decreased and saturated in the strain range of ε eq = 0–4.2 accompanied by the development of an A -fiber shear texture and an increase in the microhardness. Continuous and discontinuous dynamic recrystallization were the main mechanisms for this grain refinement. Second, the grain size increased and the texture changed to a B -fiber texture between ε eq = 4.2 and 10.2 producing a drop in the microhardness, where this grain growth was attributed to a strain-induced grain boundary migration. The mean grain size decreased and saturated again over the strain range of ε eq = 10.2–205 where there was a weak but stable texture and a microhardness evolution following a model of hardening without recovery. Finally, the separate contributions of grain size, dislocation and texture strengthening to the overall hardening behavior were critically examined. • HPT produces a grain refinement from 121 to 0.45 μm after ε = 205. • Grain refinement involves 2 stages at ε = 0–4.2 and 10.2–205. • There is grain growth between ε = 4.2 and 10.2. • The CDRX and DDRX mechanisms are responsible for the grain refinement. • Texture shifts from A -fiber to B -fiber, becoming weak but stable in the second stage. [ABSTRACT FROM AUTHOR]

Highlights: [•] ARB led to a strong grain refinement (down to 0.5μm) and homogeneity upon straining. [•] The fraction of high-angle boundaries is ∼60% in the alloy after ARB. [•] The texture after ARB is characterized by typical C shear component near the surface. [•] Copper/Dillamore component is observed at the mid-thickness of the sheets. [ABSTRACT FROM AUTHOR]

The characterization of microstructure and texture development of binary Mg-0.3Ce (wt%) after equal-channel angular pressing (ECAP) processing via route Bc at 300 and 350 °C through 4 passes were investigated using electron backscatter diffraction (EBSD) measurements. The results demonstrated an effective grain refinement from millimeter range to 6.7 and 8.3 μm obtained after 4 passes at 300 and 350 °C, respectively. The grain refinement was obtained through dynamic recrystallization (DRX). At 300 °C, DRX occurred at low strain by twin-induced dynamic recrystallization (TDRX) and particle stimulated nucleation (PSN) mechanism and then converted with increasing strain to sub-grain development (SD) and grain boundary bulging dynamic recrystallization (GBBDRX). Besides, grain growth occurred during processing at 350 °C. The texture development strongly depends on the strain level, deformation temperature and DRX mechanisms. At 300 °C, a typical basal texture with a deviation of 40° towards extrusion direction was formed gradually up to 4 passes while a completely different texture was formed at 350 °C due to the large grain size. • Mg-0.3Ce alloy was processed by ECAP for 4 passes at 300 and 350 °C using route Bc. • Significant grain refinement was obtained after 4 passes due to DRX. • At low strain DRX occurred via TDRX and PSN mechanisms. • With increasing strain, SD and GBDRX mechanisms dominate the DRX processing. • Texture evolution strongly depends on the strain, temperature and DRX mechanisms. [ABSTRACT FROM AUTHOR]

The microstructure and texture evolution of an AZ31 alloy were investigated after hot rolling and subsequent annealing using electron backscatter diffraction (EBSD). First, the alloy was hot-rolled at 350 °C up to low, medium and high strain (20, 50 and 85% of thickness reduction, respectively). The alloy samples where then annealed at 350 °C for 2, 10 and 60 min. The effect of strain level and annealing on corrosion behavior in seawater was also evaluated using electrochemical tests. At low strain, the microstructure was characterised by the absence of twinning, mainly due to the prior thermo-mechanical history of the as-received alloy. However, various modes of twinning were observed at medium strain. At high strain, the dynamic recrystallization process resulted in a microstructure with a typical basal texture. The results demonstrate that twins are responsible for the deviation of {0002} basal poles from normal towards the transversal direction. Annealing at 350 °C for up to 60 min led to normal grain growth in all the samples. In medium and highly strained samples, the deformation texture was retained, while the low strain sample underwent noticeable changes due to the absence of dynamic recrystallization. A synergetic effect of grain refinement and texture weakening was responsible for the alloy's enhanced corrosion resistance. • Twins and DRX strongly affected the deformation texture of the hot-rolled AZ31 alloy. • Annealing at 350 °C up to 60 min led to normal grain growth. • Grain refinement and texture weakening was responsible for the corrosion resistance enhancement. [ABSTRACT FROM AUTHOR]

Experiments were conducted to evaluate the evolution of the stored energy in grains with shear texture orientations A 1 * {111}< 1 ̅ 1 ̅ 2>, A 2 * {111}<1 2 ̅ 1>, A {111}<1 1 ̅ 0>, A ̅ {111}<0 1 ̅ 1>, B {112}<1 1 ̅ 0>, B ̅ {112}<1 1 ̅ 0>and C {100}<110>for Cu-2.5Ni-0.6Si and Fe-36Ni (wt%) alloys after high-pressure torsion (HPT) processing up to 10 turns at ambient temperature using a Kernel Average Misorientation (KAM) approach. A typical stable shear texture developed in the Cu-2.5Ni-0.6Si alloy immediately after 1 turn whereas there was a continuous transformation of texture in the Fe-36Ni alloy up to 10 turns. The results show that HPT processing produces similar stored energies of ~35 J/mol and ~24 J/mol but with different shear texture components for the Cu-2.5Ni-0.6Si and the Fe-36Ni alloy, respectively. The stored energy in all shear components for the Cu-2.5Ni-0.6Si alloy increases with increasing HPT processing up to 1 turn and then slightly decreases through 10 turns. By contrast, the stored energy of the Fe-36Ni alloy continuously decreases with increasing numbers of HPT turns. These evolutions are examined with reference to the initial textures, dynamic recrystallization, grain refinement mechanisms and differences in the stacking fault energies. • Stored energy correlated with shear components was inspected for Cu-Ni-Si and Fe-Ni. • Texture difference is associated with the γ SFE and the initial textures. • HPT produced the same amount of stored energy in the different shear components. [ABSTRACT FROM AUTHOR]