Showing papers on "Texture (crystalline) published in 2022"

Influence of out-of-plane stretch forming induced different strain paths on micro-texture evolution, slip system activity and Taylor factor distribution in Al–Li alloy

Abstract: A detailed investigation on the microstructure and micro-texture evolution in Al–Li alloy has been carried out following deformation at various strain paths. The stretch forming tests have been conducted to achieve three distinct strain paths, viz. close to uniaxial, plane strain and equi-biaxial. A correlation has been established between the microstructural and micro-textural developments with the various strain paths. The development of Brass {110} and Cube {001} components during uniaxial deformation and evolution of Goss component {110} with development of //ND fiber during equi-biaxial deformation have been observed as stable orientations. Meanwhile, a marginal strengthening of R {214} and S component {123} is noticed during plane strain deformation. The deformation micro-texture and associated active number of slip systems under different deformation modes are simulated using visco-plastic self-consistent (VPSC) polycrystalline model. During uniaxial deformation, the availability of the least number of active slip systems leads to the development of a relatively stronger micro-texture. Moreover, a detailed insight into the Taylor factor has been performed to elucidate its distribution based on the micro-textural developments along the three deformation paths. The higher fraction of grains in Taylor factor range M ∼ 2–3 during uniaxial and plane strain deformation is associated with the presence of Cube component {001} . On the contrary, the higher fraction of grains in Taylor factor range M ∼ 3–4 during equi-biaxial deformation is related to the strengthening of //ND fiber. The fewer number of grains in Taylor factor range M ∼ 4–5, as observed during plane strain deformation, is attributed to the evolution of Brass texture {110} .

Formation of an abnormal texture in Mg-Gd-Y-Zn-Mn alloy and its effect on mechanical properties by altering extrusion parameters

Abstract: The Mg-8Gd-4Y–1Zn–Mn (wt%) alloys prepared by semi-continuous casting and homogenizing treatment were extruded using different extrusion ratios and subsequent cooling processes. The microstructure, texture and mechanical properties of extruded alloys were investigated. The dynamic recrystallization process is promoted by increasing the extrusion ratio, while the static recrystallization process is suppressed by subsequent water cooling rather than air cooling. When the recrystallization ratio is relatively low, the non-recrystallized region showing a fiber 10 1 ‾ 0 >Mg//extrusion direction (ED) texture component dominates the texture characteristic. With the increase of the recrystallization ratio, the recrystallized region exhibiting an abnormal Mg//ED texture gradually dominates the texture characteristic. The grain boundary energy anisotropy and the grain boundary mobility anisotropy are assumed to be changed by the Gd and Y addition, which affect the preferential growth of the abnormal Mg//ED oriented grains and eventually lead to the formation of abnormal texture component. The as-aged alloy extruded at the extrusion ratio of 6 followed by air cooling shows the highest strength. The extruded alloys with an intensive abnormal texture component exhibit the best mechanical isotropy in both as-extruded and as-aged conditions. The differences in strength along different directions are mainly resulted from the fiber strengthening.

Synergistic effects of hybrid (HA+Ag) particles and friction stir processing in the design of a high-strength magnesium matrix bio-nano composite with an appropriate texture for biomedical applications.

Abstract: In this work, the effects of hybrid (HA + Ag) particles and triple-pass friction stir processing on the microstructure, texture, hardness, and tensile behavior of magnesium matrix bio-nano composite were investigated. The results showed that the mean grain size of samples was in the range of 1–5 μm owing to the occurrence of dynamic recrystallization and suppression of grain growth by second phase particles. All samples exhibited uniform dispersion of particles in the magnesium matrix caused by triple-pass FSP. However, some agglomerations were visible in the microstructure of AZ91/nHA nanocomposite. The average grain size of the AZ91/nHA/smAg sample (1.4 μm) was smaller than that of the AZ91/nHA/mAg sample (2.1 μm), which was attributed to the formation of higher content of MgxAgy precipitates in the AZ91/nHA/smAg composite. By performing the FSP, the content of Mg17Al12 was significantly decreased due to the dissolution of beta into the alpha caused by the breakup effect of mechanical stirring and temperature increase of samples. The AZ91/nHA/smAg sample had the highest texture parameter for the { 10 1 ‾ 1 } orientation as the high corrosion resistance texture. This was due to the promoting the non-basal slip caused by the dissolution of smAg particles in the magnesium matrix. After the FSP, the microhardness distribution of AZ91, AZ91/nHA, AZ91/nHA/mAg, and AZ91/nHA/smAg samples tended to be uniform and the average hardness was improved owing to the fragmentation of beta particles, grain refinement, and homogeneous dispersion of second phase particles. Compared with the AZ91/nHA/mAg sample, an increase in ultimate tensile strength (291.7 MPa), and a decrease in total elongation (5.6%) and energy absorption (12.3 J/cm3) were observed in the AZ91/nHA/smAg sample due to the formation of a higher content of the silver-rich precipitates in the AZ91/nHA/smAg sample during cooling caused by the higher solubility of silver submicron particles. The fracture surfaces of all processed samples consisted of a large number of fine equiaxed dimples (ductile fracture) owing to the grain refinement and the presence of fine second phase particles.

Microstructure dependent dislocation density evolution in micro-macro rolled Al2O3/Al laminated composite

Abstract: Flake powder metallurgy (FPM) combined with micro/macro-rolling (MMR) was employed to fabricate Al2O3/Al laminated composites with high dislocations storage capability. The effect of deformation mode on the laminated ultrafine grain structure and on the dislocations density was analyzed. Additionally, a model based on microstructure and processing parameters is proposed to describe the effect of size, aspect ratio and crystallographic textures of the matrix grains on dislocation density. It was shown that the dislocation density depends on Al2O3 dispersion degree and Al2O3-Al interfacial bonding level. They are further driven by mechanical micro-rolling process, as well as grain refinement, crystallography texture, and high aspect ratio resulted from macro-rolling process. It was demonstrated that the MMR process provides the laminated ultra-fined grains (UFGs) with higher dislocation storage capability with respect to equiaxed grains. The described process provides a good coordination between the Al2O3 dispersion, Al2O3-Al interfacial bonding as well as crystallographic textures, size and shape of the matrix grains.

Thin-gauge non-oriented silicon steel with balanced magnetic and mechanical properties processed by strip casting

Abstract: Thin-gauge non-oriented silicon steel with high strength was successfully processed using strip casting. Texture evolution and strengthening mechanism via nanoscale Cu-rich precipitates were studied to fundamentally understand the balanced combination of magnetic properties and mechanical properties. Coarse equiaxed grains with average size of ∼190 μm and relatively random texture were formed in the as-cast strip, which contributed to the inhomogeneous deformation, resulting in high density of shear bands. Exact Cube was retained from the initial Cube texture and new Goss was formed during the heavy rolling process in the 0.20 mm cold rolled sheet, which promoted relatively strong Cube and Goss texture after recrystallization annealing. The 0.20 mm annealed sheet exhibited high magnetic induction of 1.709 T, which corresponds to the high texture factor of 0.5. The total iron losses were significantly reduced with decrease in thickness, and the P1.5/50, P1.0/400, and P1.0/1000 in 0.20 mm sheet were as low as 2.63, 15.17 and 55.63 W/kg, respectively, which showed a good match between magnetic induction and iron loss. During the aging process, both the magnetic induction and total iron loss exhibited relatively good stability. With increase in aging time, the yield strength first rapidly increased and then slightly decreased. In 0.20 mm sheet, peak yield strength of ∼630 MPa was obtained on aging at 550 °C for 90–120 min. The key mechanism of precipitation strengthening was attributed to the difference in modulus and coherency strain associated with high density of nanoscale precipitates of ∼5 nm. The study revealed that the nanoscale Cu-rich precipitates can be adopted as effective approach to increase the yield strength over ∼100 MPa without deteriorating iron loss in thin-gauge non-oriented silicon steel by strip casting, which guaranteed the balance of magnetic properties and mechanical properties to meet the requirements of high-speed motor.

Microstructure, texture and mechanical properties of the rolled high modulus Mg-Y-Zn-Al-Li alloy

Abstract: In our previous work, we designed a new as-cast Mg–Y–Zn–Al–Li alloy with a high elastic modulus of 52.9 GPa. The alloy was further subjected to hot deformation under different rolling reductions (40% and 80%) in this work. The microstructure evolution, texture and mechanical properties of Mg–Y–Zn–Al–Li alloy compared with Mg–Y–Zn alloy were systematically investigated. The result showed that the Mg–Y–Zn–Al–Li alloy with a rolling reduction of 40% displayed a more homogeneous fine microstructure and a weakened basal texture, accompanied by the formation of Al–Li and nano-precipitates Al0.9Li34.3Mg64.5Zn0.3 phase. Compared with the Mg–Y–Zn alloy, the strength and ductility of the alloy also were obviously enhanced while possessing a weak mechanical anisotropy. Grain refinement and second phase strengthening (fine Al–Li phase and nano-precipitates Al0.9Li34.3Mg64.5Zn0.3) mainly contributed to the enhanced strength. The texture weakening, low dislocation density and non-basal slip commonly guaranteed the high ductility, especially the weakened texture gave rise to the low anisotropy. When the rolling reduction increased to 80%, the volume fraction of recrystallized grains in Mg–Y–Zn–Al–Li alloy increased significantly to73.3%. As a result, the symmetry of the texture distribution around the ND was appreciably improved. In addition, the lower dislocation density and more non-basal slip in the Mg–Y–Zn–Al–Li alloy with the rolling reduction of 80% further enhanced the ductility. Simultaneously, the anisotropic degree of mechanical was effectively minimized, which was mainly attributed to the weak symmetric texture caused by fine DRXed grains with random misorientation and non-basal pyramidal slip.

Texture role in the mechanical property improvement contributed by grain refinement for Mg-2.6Nd-0.55Zn-0.5Zr alloy subjected to extrusion process

Abstract: This work successfully fabricated the fine-grained Mg-2.6Nd-0.55Zn-0.5Zr (wt%) alloy plates with the average grain sizes of 2.39–3.49 μm via the extrusion process. The microstructure evolution during extrusion process and the associated mechanical properties were investigated. Results showed that dynamic recrystallization (DRX) significantly refined the grain size and improved the microstructure homogeneity. Extrusion fragmentation effect on the coarse Mg12Nd particles contributed to the development of fine-grained uniform microstructure, especially at the lower extrusion temperature. Additionally, extrusion process turned the fiber basal texture into the double peak basal texture owing to the sequential deformation mode activation from basal slip and tension twinning to pyramidal slip. Subsequent continuous DRX and particle-stimulated nucleation (PSN) recrystallization played a weakening effect on the double peak basal texture. Moreover, decreasing the extrusion temperature increased the activation difficulty of pyramidal slip and weakened the effect of PSN on texture modification, leading the basal plane distribution along the extrusion direction to be strengthened. Fine-grained strengthening significantly improved the mechanical properties, but such strengthening capability was severely dependent on the texture. During tension deformation, the weak basal texture easily activated the basal slip whereas the strong basal texture needed to activate the prismatic slip. Hall-Petch analysis indicated that the higher yield stress in the strong basal texture was ascribed to the remarkable deformation mode strengthening (activation of prismatic slip) and the geometrical strengthening (higher Taylor factor). The weak basal texture was beneficial to improve the uniform elongation owing to the higher strain hardening ability, which was more obvious when the tension twinning was activated.

Investigation of microstructure, crystallographic texture, and mechanical behavior of magnesium-based nanocomposite fabricated via multi-pass FSP for biomedical applications

Abstract: In this work, the microstructure, crystallographic texture, hardness, and tensile behavior of AZ91/HA bio-nano composite manufactured by multi-pass friction stir processing (FSP) were investigated. With increasing the number of FSP passes, the average size of grains is reduced. The processed AZ91 and AZ91/HA nanocomposite after the third pass had the lowest grain size (4.5 and 2.6 μm, respectively). Also, the average grain size of composites was smaller than that of monolithic samples at the same pass number. The results showed that particle distribution in the AZ91/HA nanocomposite is significantly affected by the number of passes. The increment of the pass number led to a more uniform dispersion of HA nanoparticles in the matrix due to more plastic flow of materials. With increasing the pass number to three, the accumulated strain increased to 0.726 (monolithic) and 0.623 (composite) due to repeating mechanical stirring. There was a texture transition ( { 10 1 ‾ 1 } to { 0002 } ) via performing only one pass of FSP. Suppression of grain rotation by HA nanoparticles maintained the intensity of { 10 1 ‾ 1 } texture as a corrosion-resistant orientation after the third pass. With increasing the pass number of FSP, the hardness and strength of samples increased due to the grain size reduction and the more uniform dispersion of HA powder. The composite sample after the third pass exhibited the highest hardness of 117.0 HV and ultimate tensile strength of 306.6 MPa. The failure mode of processed samples was ductile. There were smaller dimples on the fracture surface of the composite samples due to their lower grain size and also the presence of HA nanoparticles. Considering the obtained results, the nanocomposite after the third pass can be a good load-bearing implant for biomedical applications.

Charpy impact anisotropy and the associated mechanisms in a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate

Abstract: The Charpy impact absorbed energy of a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate with different sampling and notching directions was investigated. Strong anisotropic variations occurred in impact absorption energies due to difference of the α phase crystal orientation and microstructural characteristics along different directions. The higher crack propagation energy of the sampling-notching direction sample (RD-ND) resulted in an impact absorption energy of approximately 2.5 times larger than that of the TD-ND, TD-RD and RD-TD samples. Based on the analysis of the α crystal orientation and the TEM microstructure after impact deformation, it was found that the higher absorption energy of the RD-ND sample was attributed to the activities of a large number of { 10 1 ‾ 0 } ⟨ 1 2 ‾ 10 ⟩ prismatic slips and the resistance created by grain boundaries against crack propagation, which also resulted in the delamination of the impact fracture surface. Finally, the coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms of the hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy was described.