Deformation Texture Research Articles

Effect of strain path change on static recrystallization behavior of AT63 magnesium alloy

The present work has examined the influence of strain path change on the static recrystallization process of Mg-6Al-3Sn (AT63) magnesium alloy. The samples were deformed at ambient temperature for three conditions; unidirectional rolling (UDR), clock cross rolling (CCR), and forging. The microstructural features of deformed and recrystallized samples at different conditions were characterized through optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), hardness testing, and X-ray diffraction (XRD). The results suggest that the recrystallization predominately started at the prior grain boundaries and within the twin boundaries. A significant reduction of the grain size from 83 µm to ∼ 7 µm was observed after recrystallization. The recrystallization kinetics was relatively slower for CCR samples. It was attributed to the level of stored energy in the material, initial deformation texture, and evolution of fine precipitates.

Effect of extrusion temperature on microstructure, mechanical properties, and deformation mechanism of Mg-2.5Er-0.6Zr alloy

Different extrusion temperatures (350 °C, 380 °C, 410 °C) were used to forward extrude the cast Mg-2.5Er-0.6Zr (wt.%) alloy. The effects of extrusion temperature on the microstructure, mechanical properties, deformation texture and extrusion deformation mechanism of Mg-2.5Er-0.6Zr alloy were studied by OM, SEM, room temperature tensile test, EBSD and IGMA analysis. The results show that the cast alloy has coarse grains and exhibits random texture characteristics. After extrusion, the alloy underwent dynamic recrystallization (DRX), and the equiaxed grains were refined, forming a special rare earth texture, and the mechanical properties of the alloy were greatly improved. In the temperature range of 380 °C–410 °C, with the increase of extrusion temperature, the alloy grain coarsing, strength and plasticity gradually decrease, but it is still much higher than the cast alloy. Under the combined influence of fine grain strengthening, texture weakening and diversified plastic deformation modes, the comprehensive mechanical properties of extruded Mg-2.5Er-0.6Zr alloy are the best at 380 °C, and its ultimate tensile strength, tensile yield strength and elongation are 218.7 MPa, 184.2 MPa and 44.1%, respectively.

Insight into the spatial distribution and interaction model of heat-induced micro- and nano-starch/myofibrillar protein blends

This work investigated the gelatinizing and hydration properties of raw and milled tapioca starches at micron and nano scale as well as their effects on gelation of myofibrillar proteins (MP) from Ctenopharyngodon idellus by analyzing rheology, texture and microstructure of heat-induced MP/starch blends. Milling induced starch granules damage to micron and nano scale, causing a fall in starch swelling power and a jump in water solubility. Among raw and milled starches, nano-starch had the best reinforcement effect on MP gel, i.e., MP/nano-starch showed the lowest critical gel concentration, highest G', strongest resistance to deformation and highest texture performance. Correlation analysis revealed that starch water solubility was responsible for the reinforced MP gel rather than starch swelling power. A schematic model was proposed for illustrating the interaction of starches and MP. All the blends had the ordered filamentous network as the basic skeleton, with some starches (granules and their fragments) in the voids or on the edge or surface of MP filaments as inert fillers, and some (chain segments) embedded in the filaments as active fillers. Almost all nano-starch were actively filled into the MP filaments to enhance the strength of filaments, thus achieving the best reinforcement effect on MP gel.

Effects of microalloying with Ag, Li, and Sc on hot-deformed microstructure of Al–Mg–Si–Cu alloys

The effects of microalloying with Ag, Li, and Sc on the hot-extruded microstructures of Al–Mg–Si–Cu alloys were studied. Each microalloying element was observed to affect the hot-deformed microstructure of the alloy, with a retarding effect on its recrystallization; however, the effect of Ag-addition was relatively small. The number fraction of grains with a high Taylor factor and their kernel average misorientation significantly increased when Li and Sc were added to the Al–Mg–Si–Cu alloy, implying a strong anisotropy of slip. It was also found that Li-addition primarily weakened the C component, whereas Sc-addition significantly strengthened the rotated copper (Rt-Cu) component in the deformation texture, and strongly dissipated the recrystallization texture. Additionally, all the microalloying elements slightly increased the dislocation density and fraction of edge dislocations. Thus, a very close dislocation arrangement with a strong screening of dislocations was observed; however, this effect was relatively weak for the Sc-added alloy. The high variation in the microstructural parameters of the Sc-added alloy was understood to depend primarily on the Al3Sc dispersoid and its effect on the other precipitates. In contrast, Ag- and Li- additions did not significantly change the relatively large precipitate structure, which implies that there were changes in the nanoscale precipitates or solute clustering during the hot deformation of Ag- and Li-added alloys.

Experimental and numerical investigation on interface microstructure and phase constitution of radiation resistant Pb/316L stainless steel explosive welded composite plate

As one of the shielding materials, lead (Pb) and its alloy exhibit excellent ray absorption and radiation shielding ability due to its high density and atomic mass. In this work, the explosive welding technique was successfully performed to join Pb/316L dissimilar metals. To revel the microstructure characteristics and phase constitution of the joining interface, the electron backscattered diffraction test and numerical simulation were carried out. It was concluded that the slight waveform structure without obvious defects or cracks was obtained at the explosive welded interface. The fine grains zone, sub-grains and twin structures were formed due to the severe plastic deformation. Meanwhile, the recrystallized structures, substructures and deformed structures were also confirmed at the joining interface during the high strain rate impact. In addition, five different deformation textures and recrystallization textures were confirmed due to severe plastic deformation and dynamic recrystallization. Furthermore, the numerical simulation results also showed a slight waveform structure at the Pb/316L explosive welded interface, which was consistent with the experimental results.

Microstructure, Texture Evolution, and Aging Behavior of a Cold‐Rolled Ti–B20 Alloy

The microstructure, texture evolution, and aging behavior of a cold‐rolled (CR) Ti–B20 alloy are investigated in this work. The results show that the microstructure of the solution‐treated (ST) Ti–B20 alloy consists of equiaxed recrystallized grains and exhibits typical {001}<110> and {001}<100> textures. After cold rolling, the initial equiaxial grains are stretched along the rolling direction (RD), which can produce typical deformation textures of γ‐fiber {111}<112> and {111}<110> textures. For the CR samples after aging treatment, small amounts of needle‐like or spherical α‐phases preferentially precipitate in the grain boundaries of deformed β grains during aging treatment; many nanosized α‐phases uniformly precipitate in the grain boundaries and inside the β grains. A high dislocation density is generated in CR samples, promoting α‐phase nucleation, increasing the volume fraction, and decreasing the α‐phase size during aging treatment.

Correlation of microstructure, texture and intermetallic particles during multi-step cross-rolling and annealing in a strip-cast AA8011 alloy

In multi-step cross rolling (MSCR), twin roll cast (TRC)/strip-cast AA8011 aluminum sheet was cold-rolled up to 72 % thickness reduction by rotating +/- 90º with respect to normal direction (ND) after each rolling pass. The intermetallics particle size after MSCR got reduced to ∼ 0.5–3 µm compared to unidirectional cold rolling (UCR) ∼ 1.5 – 4.5 µm (Kumar et al. 2018) after the same thickness reduction of 72 %. Subsequently, it was annealed at 375 ºC for varying times (1–240 min). Both investigations (UCR/MSCR) showed no removal of centerline segregation (CLS) of Al-Fe-Si intermetallics. After 72 % cold rolling (UCR/MSCR), deformation texture (i.e., Brass (Bs) {110} < 112 > , copper (Cu) {112} < 111 > , Goss {110} < 011 > and S {123} < 634 > ) strengthened at the expense of Cube {100} < 001 > . However, cube improves during annealing at 375 ºC after MSCR than UCR. Moreover, it was observed that particle-stimulated nucleation (PSN) (intermetallics particle size ≥ 2 µm) played an important role in promoting random texture. For instance, the % volume fraction of Brass, Copper, Goss, S, Cube were 6.1 %, 5.3 %, 3.7 %, 9.0 %, 4.8 % (Kumar et al. 2018) and 6.5 %, 3.6 %, 1.9 %, 7.7 %, 5.3 % for UCR and MSCR, respectively. Hence, MSCR effectively reduces intermetallic particles size, decreases the overall anisotropy and improves the recrystallization texture (especially Cube component of texture) of TRC AA8011 aluminum alloy.

The interface microstructure and phase constitution of Nb/316L composite plates fabricated by explosive welding

ABSTRACT Niobium has a reputation for its superior superconducting, high strength and corrosion resistance at elevated temperatures. In this work, the explosive welding technique was successfully performed to join Nb/316L dissimilar metals. To reveal the phase constitution and texture distribution at the joining interface, the EBSD test was carried out. It was concluded that an irregular large wavy structure of fine crystal, sub-grains and twin structures was formed. In addition, the recrystallised structures, substructures, deformed structures and local internal stress at the joining interface were attributed to severe plastic deformation and rapid solidification of liquid metal. Furthermore, six different deformation textures and recrystallisation textures were confirmed at the joining interface due to severe plastic deformation and dynamic recrystallisation.

Effect of tool pin geometry and multi-pass intermittent friction stir processing on the surface properties of aerospace grade aluminium 7075 alloy

Multiple pass intermittent friction stir processing was conducted on the surface of an aerospace grade AA7075 alloy using pentagonal and hexagonal profiled pins and its microstructural evolution and mechanical properties were investigated. Results showed a defect-free cross-section with better material mixing for the specimens processed using pentagonal pin. Application of 6 intermittent friction stir processing passes reduced average grain size to 2.32 μm as a result of dynamic recrystallization. Texture index improved after 6 intermittent friction stir processing passes with a higher volume of deformation textures. Microhardness and tensile strength of the alloy increased to 125.5 HV, and 476 ± 10 MPa after 6 intermittent friction stir processing passes due to precipitation strengthening, grain refinement, and dislocation density. Fracture surface investigation revealed an intergranular mode of failure.

Cellular Automaton‐Based Modeling of Recrystallization Texture Considering Instability Criterion and Nonuniform Boundary Mobility in AA1100 Aluminum Alloy

Herein, the nucleation instability criteria and nonuniform mobility are considered in the 2D cellular automaton simulation to investigate the recrystallization texture of cold‐rolled AA1100. Under the consideration of mechanical instability, the critical driving force for nucleation depends on the differences of the stored energy between a center cell and the neighboring cells. The possible nucleation sites are reduced to 37.5% in comparison with the nucleation model using a constant value of the driving force. The simulation of nucleation reveals that the mechanical instability promotes the formation of recrystallization textures at the expense of neighboring grains with orientations of deformation textures. The nonuniform mobility of high‐angle grain boundaries is implemented in simulation of recrystallization. The enhanced mobility of high‐angle grain boundaries with misorientation of 40°/&lt;111&gt; significantly promotes the growth of grains with orientations of Cube and (recrystallization textures) and inhibits the growth of grain with orientations of C, S, and B (deformation textures).

Effect of Sr microalloying on microstructure and corrosion resistance of Al–4.6Mg alloy

AbstractThe effect of Sr on the microstructure of Al–4.6Mg alloy is studied via optical microscopy, scanning electron microscopy‐energy‐dispersive analysis, electron backscattered diffraction, transmission electron microscopy, and the intergranular corrosion susceptibility is evaluated according to ASTM G67. The main precipitation phases of Al–4.6Mg alloy are β‐Al3Mg2 and Al6Mn, with a new square phase of Al3Mn also being formed. After the addition of Sr, the β‐Al3Mg2 phase of the alloy decreases, the morphology changes, and Al4Sr and τ‐Al38Mg58Sr4 phases are formed. Accordingly, the nanoscale precipitation phase τ‐Al38Mg58Sr4 is uniformly distributed inside the grains. Microstructure analysis shows that Sr promotes the dynamic recovery and dynamic recrystallization of the alloy, inhibits the growth of recrystallized grains, and reduces the alloy grain size from 14.294 to 10.273 μm. Additionally, the low‐angle grain boundaries increase, the high‐angle grain boundaries decrease, the texture of the rotated cube r‐{001}&lt;110&gt; improves, and the deformation texture decreases. The IGC susceptibility of the alloy is reduced with the addition of Sr, and the corrosion resistance in an electrolyte containing NaCl is enhanced.

Effect of parent β-texture on α-texture evolution during dynamic precipitation in a continuous forging process of Ti-6Al-4V alloy

The α-texture evolution during dynamic precipitation in a continuous forging process was investigated in Ti-6Al-4 V alloy. The relationship between α-phase transformation texture and deformation texture was studied. It was found that the {10−10} transformation texture gradually weakened during deformation, and the texture intensity was lower than that of traditional β-forging and (α + β)-forging under a constant deformation strain. In addition, it was also observed that the (001) parent β-texture led to a weaker {10−10} α-texture development than the other β-textures. According to the Schmid factor (SF) analysis, the α-lath in the (001)//FD parent β-grains exhibited a higher SF value of the {10−10}< 11–20 > prismatic slip system than that in the other β-grains. The high-dislocation-density region locally appeared in the α-lath under the activation of prismatic slip system, which led to inhomogeneous deformation and partial lattice rotation. Therefore, the misorientation angle developed within the α-lath and the {10−10} transformation texture was weakened.

Experimental and numerical investigations on interface microstructure characteristics and wave formation mechanism of Sn/Cu explosive welded plates

ABSTRACT The interface characteristics and formation mechanism of explosive welded waveform structures still lack a detailed and in-depth research. Thus, a combination of advanced characterization and numerical simulation methods were performed in this study to investigate the phase constitution, texture distribution, 3D interface morphology and wave formation mechanism of Sn/Cu explosive welded interface. The microstructure analyses indicated that the typical waveform structures composed of fine crystal band and elongated grains zone were formed at the Sn/Cu joining interface. The dynamic recrystallized structures and local high strain at the waveform were attributed to severe rheological deformation and rapid solidification of liquid metals. In addition, the S, copper, brass and fiber deformation textures and the cube and gross recrystallization textures were found. The CT results indicated the 3D Sn/Cu joining interface morphology presents a regular convex waveform feature, which is related to periodic pulse load caused by explosive detonation. Furthermore, based on the simulation results, the 2D joining interface presents similar experimental waveform structure, and the 3D interface evolution characteristic was consistent with the shock wave propagation characteristics on the flying plate to some extent, which was in good agreement with the experimental results.

Mechanism of Plastic Deformation of As-Extruded AZ31 Mg Alloy during Uniaxial Compression

The deformation mechanism and texture evolution of AZ31 Mg alloy compressed in three different directions at room temperature were studied, and the relationship between the two was compared through experiments and viscoplastic self-consistent (VPSC) modeling. Setting up only one specific deformation mode was the predominant mechanism by changing the CRSS ratio for the different deformation modes. The following conclusions were drawn: (1) It was demonstrated that basal slip causes a slow and continuous deflection of the grain toward the transverse direction (TD). When the sample is compressed in the extruded direction (ED), prismatic slip leads to grains being deflected toward the ED in the initial stages of compression, and when the sample is compressed 45° to the extrusion direction (45ED) and perpendicular to the extrusion direction (PED), prismatic &lt;a&gt; slip contributes little to the texture evolution. (2) When the sample is compressed along three different directions, pyramidal &lt;c+a&gt; slip leads to the grain being deflected toward the normal direction (ND), and the {10-12} extension twin deflects the grain at a large angle. (3) When only the {10-11} compression twin is activated, the grain will be deflected in the ND while the sample is compressed along the ED and 45ED, but when the sample is compressed in the PED, the grains are concentrated from both sides of the ED to the center.

Bauschinger effect in Gd micro-alloying metastable high-entropy alloy

To investigate Bauschinger effect in metastable high-entropy alloys with strain-induced FCC → HCP phase transformation, we designed a series of Gd micro-alloying non-equiatomic metastable high-entropy alloys. The results show that all tested alloys have asymmetrical tension-compression properties exhibiting the obvious Bauschinger effect, which is related to the different levels of phase transformation in compression and tension owing to different deformation textures. Excessive phase transformation suppresses the increase in pile-up density of geometrically necessary dislocations (GNDs), resulting in a back stress relaxation effect. The inverse phase transformation observed by quasi in-situ EBSD proves the instability of the HCP phase. The established kinetic model points out limitation of the classical back stress measurement method in metastable high-entropy alloys.

The Differences in Microstructure, Microtexture, and Tensile Anisotropy of Ti80 Heavy Plate Across the Thickness

Herein, the differences in microstructure, microtexture, and tensile behavior of the Ti80 heavy plate across the thickness are investigated. The Ti80 heavy plate consists of equiaxed α and transformed β grains with high degrees of recrystallization microstructures. Significant differences are observed in the main texture components between the central and surface zones. The inhomogeneous distribution of hot compression and shear leads to different deformation textures during processing. Due to temperature distribution, the combination of the variant selection mechanism and α–β phase interaction is responsible for the evolution of surface texture, while only the former plays a major role in the center. Final fracture areas of tensile samples show ductile fracture characteristics. The anisotropy behaviors in planar tensile of the Ti80 heavy plate at room temperature are evaluated. They are related to the difficulty of activating prismatic slip and basal slip , which are determined by the crystallographic texture of the material. This work helps to explore reasonable thermomechanical processing parameters and establish rolling schedules to weaken the mechanical heterogeneity across the thickness of near‐α‐titanium alloy heavy plates.

Investigation of the Hot Deformation Behavior in VDM® Alloy 780 by In Situ High-Energy X-Ray Diffraction

Ni-based superalloys are indispensable for applications in demanding environments, such as the heavily stressed rotating discs in the hot sections of modern gas turbines or jet engines. In this paper, the microstructure evolution during hot deformation to mimic the forging process was investigated in the polycrystalline VDM® Alloy 780 viain situ X-ray diffraction at temperatures of 950, 1000, and 1050 °C. For the tested temperatures, the hot forming led to subgrain formation, the built-up of a texture by rotation of the matrix grains into preferred orientations, and dynamic recrystallization. The influence of the deformation was analyzed depending on the direction of the lattice plane normals to the load direction, for the first five γ-reflections in the diffraction pattern. During uniaxial compressive deformation intensity, maxima develop in the loading direction solely for the γ-(220) reflections, while intensity minima develop for the other reflections which correspond to the formation of a <110> fiber texture. In the transverse direction, all γ-reflections except the (220) have an increased intensity at the maximum specimen strain of 20 pct. Directly after the hot forming, three different cooling rates of 10, 100, and 1000 °C/min and their influence on the microstructure were investigated. The fast and medium cooling rates lead to low recrystallized fractions and a largely preserved deformation texture, whereas the low cooling rate leads to a high recrystallized fraction and a slight remaining texture. Additionally, the diffraction data are complemented by electron microscopy measurements.

In-situ observation of microstructure and orientation evolution of the Cu–Cr–Zr-Hf alloys

The roles of Hf element in the mechanical properties, deformation mode and orientation evolution of the Cu-0.4Cr-0.2Zr-0.2Hf (wt.%) alloys were investigated using both ex-situ and in-situ electron backscatter diffraction (EBSD). The results indicate that the trace Hf element (0.2 wt%) addition into the Cu–Cr–Zr alloys motivates the multiple slip activities. The activation of multiple slip systems indirectly or directly influences the tensile strength, strain distribution and lattice rotation. Firstly, it promotes the generation of dislocations, and thus enhances the work hardening rate, contributing to the improvement of the ultimate tensile strength. Secondly, it inhibits the movement of dislocations to the grain boundaries, and thus hinders the strain localization at the grain boundaries, promoting the homogeneous deformation. Thirdly, the interaction between dislocations on different slip systems restricts the intragranular lattice rotation, leading to the high stability of the grains with Goss orientation in the Cu–Cr–Zr-Hf alloys. The mutual transform between the R-CubeRD orientation and Goss orientation is also observed. This study deepens the understanding of deformation mechanisms and texture evolution of the Cu–Cr–Zr-Hf alloys.

Texture, microstructure and mechanical properties of AA7075-graphite composites produced through mechanical alloying and hot-extrusion

This paper reports the effect of graphite and milling time on the texture, microstructure and mechanical properties of AA7075-graphite composites produced through mechanical alloying and hot extrusion. Characterization was conducted by scanning electron microcopy, transmission electron microscopy, X-ray diffraction, laser diffraction, electron backscatter diffraction and precession electron diffraction, and mechanical properties were evaluated by uniaxial tensile tests. Results show that particle and crystallite size of mechanically milled powders affect the grain size of extruded samples. Most of extruded samples exhibit deformation textures components, however, in-grain misorientation values were lower than 2°, which is an indicative of their recrystallization. The presence of deformation texture components in recrystallized samples is explained by the oriented nucleation mechanism. Hardness, yield strength (YS) and ultimate tensile strength increase, while elongation to fracture decreases, with the increase in graphite content and milling time. The size of recrystallized grains decreases with the increase in milling time and graphite content. Furthermore, YS varies with grain size according to the Hall-Petch relationship. Hardening of the investigated AA7075-graphite composites is enhanced by grain refinement, dispersion of Al4C3, Mg2Zn2 and Al2O3; and to a lesser extent by the random texture developed.

Количественный анализ текстуры деформации и первичной рекристаллизации при угловой прокатке и отжиге магнитострикционного сплава (Fe83Ga17)99B1

The Fe–Ga alloy is a promising magnetostrictive material thanks to of the optimal combination of functional properties and relatively low price due to the absence of rare-earth elements in the composition. To obtain the maximum magnetostriction in Fe–Ga polycrystals, it is necessary to create a crystallographic texture with a predominance of the &lt;100&gt; direction, since the tetragonal magnetostriction constant is the largest. Traditional methods of thermomechanical treatment do not lead to the formation of such a texture in a bcc alloy. In this paper, for the first time, the authors propose to use inclined rolling to increase the proportion of favorable texture components. Warm rolling with a deformation degree of 70 % was carried out at angles of 0, 30 and 90° to the direction of hot rolling. The deformation texture was examined using X-ray texture analysis and the texture and structure of the material after recrystallization was analyzed by electron backscatter diffraction (EBSD) on a scanning electron microscope. Quantitative texture analysis was carried out using the orientation distribution function (ODF) method using the ATEX software. The volume fraction of some texture components was calculated. The study shows that a significant change in the deformation textures and primary recrystallization occurs during rolling at an angle of 90°. The sample after such rolling contains the largest amount of the planar component {100}. The study identified a relationship between the texture of deformation and recrystallization in Fe–Ga: to increase the proportion of components with the &lt;001&gt; crystallographic direction during recrystallization, the presence of planar components {111} in the deformation texture is necessary, which is associated with the predominant growth of favorable components in the deformation matrix with such a texture.