Weak Texture Research Articles

Evolution of Precipitates and Microhardness of L-PBF Inconel 625 Through Relevant Thermal Treatment

Laser powder bed fusion (L-PBF) is a metal additive manufacturing (AM) technique that produces a unique microstructure significantly different from wrought microstructure. Inconel 625 (IN625) is an alloy widely used to manufacture complex parts, but it comes with its own unique challenges. The alloy is prone to precipitation under elevated temperatures, which makes designing suitable heat treatment to tailor the desired microstructure and mechanical properties critical. Traditional heat treatment for wrought IN625 cannot be applied to L-PBF IN625; therefore, it is vital to understand the evolution of precipitates on the way to complete recrystallization. This study focuses on these precipitates in IN625 produced by the L-PBF technique. Heat treatments at 700 °C, 900 °C, and 1050 °C were performed separately to encourage the precipitation of strengthening γ″, the detrimental δ phase, and the dissolution of precipitates, respectively. γ″ precipitates were found in the as-printed condition and at 700 °C. δ precipitates were detected at 700 and 900 °C. Carbides and Al-rich oxides were observed in all conditions of L-PBF IN625. Texture analysis showed grain growth along the build direction with strong (100) texture at temperatures up to 900 °C. Weak and random texture with equiaxed grains was observed at 1050 °C, which is similar to wrought IN625.

Formation of Abnormal Texture and Anisotropy Weakening Mechanism of Mg–Gd–Y–Zn–Zr Sheets by Rotary Forward Extrusion

Formation of Abnormal Texture and Anisotropy Weakening Mechanism of Mg–Gd–Y–Zn–Zr Sheets by Rotary Forward Extrusion

A study of blind denoising algorithms for two-scale real images based on partial differential equations

In order to better preserve the details and texture information in the image, a dual scale real image blind denoising algorithm based on partial differential equations is studied. Input real image information, perform small-scale denoising based on differential curvature partial differential equations, and combine with a new diffusion coefficient function to distinguish the edges, flat areas, and noise of the image, allowing the algorithm to retain more subtle information such as weak edges and textures while removing noise. For the large-scale information in the input real image, a multi-stage partial differential equation is used for denoising processing. Based on the mixed denoising method of 8-neighborhood and implicit curvature, a weight function is constructed to control the proportion of the two types of equations in image denoising, effectively achieving the goal of large-scale image denoising. The experimental results show that in the MATLAB coding platform, this algorithm can eliminate different types of noise, preserve more edge and detail information of the image, and improve the registration and recognition accuracy in the image application process.

Effect of microstructure evolution on the corrosion behavior of extrusion-shearing Mg-3Zn-XCa-0.6Zr alloys

In order to promote the application of new biomedical materials Mg-Zn-Ca-Zr alloy, the Mg-3Zn-xCa-0.6Zr (x = 0.6, 1.2, 1.8 wt%) alloys were fabricated by an extrusion shearing (ES) process. The effect of secondary phase precipitation, grain size and texture on the corrosion resistance of Mg-3Zn-xCa-0.6Zr (wt%) in Hank's solution were studied using electrochemical, immersion and electron back-scattering diffraction (EBSD) tests, and the corrosion mechanism of ES alloys was discussed. With increasing the addition of Ca element, the grain size of alloys first decreased and then increased, and the constitution of second phase was transformed from MgZn and Ca2Mg6Zn3 phases to Mg2Ca and Ca2Mg6Zn3 phases, the texture changed from a bimodal texture intensity with stronger basal texture to a DRX texture intensity with a weaker texture. Mg-3Zn-0.6Ca-0.6Zr alloy showed the lowest corrosion rate of ∼0.3140 ± 0.0642 mm/y. The excellent corrosion resistance of Mg-3Zn-0.6Ca-0.6Zr alloy could be attributed to the High-potential dispersion distribution of MgZn and Ca2Mg6Zn3 phases and the strong basal texture. As well as more dense corrosion product films formed after alloying, effectively hindering local corrosion. In contrast, corrosion product films formed by the fine grain structure of Mg-3Zn-1.2Ca-0.6Zr alloy were not sufficient to resist the galvanic coupling corrosion between the Mg2Ca phase and the Ca2Mg6Zn3 phase, which caused the decreasing of its corrosion resistance.

6D Pose Estimation of Industrial Parts Based on Point Cloud Geometric Information Prediction for Robotic Grasping

In industrial robotic arm gripping operations within disordered environments, the loss of physical information on the object’s surface is often caused by changes such as varying lighting conditions, weak surface textures, and sensor noise. This leads to inaccurate object detection and pose estimation information. A method for industrial object pose estimation using point cloud data is proposed to improve pose estimation accuracy. During the feature extraction process, both global and local information are captured by integrating the appearance features of RGB images with the geometric features of point clouds. Integrating semantic information with instance features effectively distinguishes instances of similar objects. The fusion of depth information and RGB color channels enriches spatial context and structure. A cross-entropy loss function is employed for multi-class target classification, and a discriminative loss function enables instance segmentation. A novel point cloud registration method is also introduced to address re-projection errors when mapping 3D keypoints to 2D planes. This method utilizes 3D geometric information, extracting edge features using point cloud curvature and normal vectors, and registers them with models to obtain accurate pose information. Experimental results demonstrate that the proposed method is effective and superior on the LineMod and YCB-Video datasets. Finally, objects are grasped by deploying a robotic arm on the grasping platform.

Effects of TiB2 particles on deformation behavior, softening mechanisms and recrystallization texture of hot-compressed Fe-TiB2 composites

Fe-TiB2 composites, also termed as high modulus steel, offer a promising solution to the challenge of achieving both lightweight and high stiffness materials. However, the presence of TiB2 particles in Fe-TiB2 composites results in poor hot-workability. Therefore, understanding the effects of TiB2 particles on the hot deformation behavior, dynamic recrystallization (DRX), and microstructural evolution of Fe-TiB2 composites is crucial for optimizing their hot-working process. In this study, we elucidated the effects of TiB2 particles on deformation behavior and dynamic softening behavior by conducting a series of isothermal compression tests on as-cast Fe-TiB2 composites and as-cast base alloys (control group) at temperatures of 800–1200 °C, strains of 0.36–1.2, and strain rates of 0.01–1 s⁻1. Using electron backscatter diffraction, we characterized the microstructures of composites and base alloys, showing that TiB2 particles induce a DRX process through particle stimulated nucleation (PSN) at low temperatures and promote continuous dynamic recrystallization (CDRX) at high temperatures. The presence of TiB2 particles have significantly affected the dislocation movement and distribution, which changes the deformation energy distribution and thus facilitates different DRX behaviors under various thermal deformation conditions. Additionally, the microstructure resulting from DRX through PSN exhibits significant texture weakening and grain refinement, presenting a promising method for fabricating ultrafine-grained Fe-TiB2 composites.

Comparative study on contribution of bimodal microstructure and heterogeneous microstructure to mechanical properties of ZK60 alloy

In this work, we compared the effects of bimodal microstructure and heterogeneous microstructure on the mechanical properties and strengthening mechanisms of ZK60 alloy. The bimodal microstructure is composed of coarse un-dynamically recrystallized (un-DRXed) grains with strong basal texture and fine dynamically recrystallized (DRXed) grains with weak texture, while the heterogeneous microstructure is composed of coarse DRXed grains and fine DRXed grains. The result suggests that high-density dislocations and high-density precipitates have significant contribution to the strength. The high-density dislocations in un-DRXed grains cause the formation of an uneven distribution of precipitates in the ZK60 alloy which results in the high yield strength of 305 MPa, ultimate tensile strength of 344 MPa and elongation of 12% in the bimodal-structured ZK60 alloy. In comparison, the heterogeneous-structured ZK60 alloy lacks the strengthening effect from high-density dislocations and precipitates, and a lower YS of 226 MPa, and UTS of 305 MPa are achieved. The result also indicates the weak texture, low density of dislocations, low density of precipitates, and stronger ability of storing dislocations in coarse grains for heterogeneous microstructure are helpful to the ductility. Thus, HE sample exhibits higher elongation of 23% than BI sample. The finding shed light on the microstructure designing of high-performance Mg alloys.

Effect of isothermal annealing on yield anisotropy of AZ31 Mg alloy bars processed by ambient extrusion

Magnesium and its alloys show strong mechanical anisotropy due to their hexagonal close-packed structure. This paper processed ambient extrusion and subsequent annealing on AZ31 magnesium alloy bars to investigate the effect of working hardening and texture weakening on yield anisotropy of magnesium alloy. After ambient extrusion, yield strength on different loading direction are improved due to working hardening. ED-yield strength has the highest increment because work hardening has a higher effect on prismatic slip. Then, yield anisotropy becomes stronger with the increase of extrusion train. During annealing, static recrystallization occurs firstly in {101‾1} twinning zones and producing recrystallized grains with random orientation. With the growth of recrystallized grains, basal fiber texture is weakened gradually. Such weak basal texture can promote the activation of basal slip when loading along ED, so ED-yield strength shows a high decrement. On this way, the yield anisotropy in AZ31 magnesium alloy bars is weakened through ambient extrusion and subsequent annealing.

Achieving microstructural homogeneity in the stir zone across thick AA6061 welds using self-reacting bobbin tool friction stir welding

This study focuses into strategizing the usage of self-reacting bobbin tool friction stir welding (SRBT-FSW) to obtain consistent microstructural homogeneity along the thickness of AA6061 aluminium alloy (AA) thick plates during welding. The SRBT-FSW technology, distinguished by its dual-shoulder design, represents a significant step forward in FSW by eliminating the requirement for a backing anvil and promoting balanced heat distribution. This study seeks to address the issues of maintaining uniform microstructural characteristics throughout the weld zone, which is crucial for the mechanical performance and durability of welded joints in structural applications. The experimental study entails the systematic welding of AA6061 plates of 6 mm thickness using a self-reacting bobbin tool under a fixed processing condition. Electron backscatter diffraction (EBSD) was used to characterize the grain structure and phase distribution over the weld. Mechanical parameters like as tensile strength and hardness were determined to establish correlations between microstructure and mechanical performance. The results demonstrated that SRBT-FSW significantly enhances microstructural homogeneity across the weld zone, leading to improved mechanical properties. In the Bottom Zone (BZ), a refined grain structure with an average grain size (AGS) of 3.53 µm and a random or weak texture was observed, contributing to enhanced hardness and mechanical performance, with an ultimate tensile strength (UTS) of 220 MPa. In contrast, the Top Zone (TZ) exhibited a coarser AGS of 4.33 µm with a pronounced {111} crystallographic texture, resulting in a slightly lower UTS of 205 MPa. The Middle Zone (MZ), influenced by the greater heat input from both the TZ and BZ, showed an intermediate AGS of 3.99 µm, predominantly oriented along the {101} plane, and achieved a UTS of 194 MPa, with a slight reduction in ductility. This study highlights the potential of self-reacting bobbin tool friction stir welding as a reliable method for making high-quality, homogeneous welds in thick aluminium plates and paving way for their wider application in the aerospace, automotive, and shipbuilding industries, where homogeneous microstructural qualities are of significant importance.

Superplastic deformation mechanisms of coarse-grained rolled Mg-4Y-3RE magnesium alloy

The Mg-4Y-3RE (WE43) magnesium alloy possesses significant advantages such as high specific strength, excellent shock absorption, strong electromagnetic shielding capabilities and recyclability. However, its close-packed hexagonal structure leads to poor plasticity at room temperature, which limits its broader engineering applications. Therefore, superplastic forming at high temperatures is used to manufacture the components from this alloy. This study conducted tensile tests on hot-rolled WE43 rare-earth magnesium alloy with coarse grains at various temperatures and strain rates. The high-temperature superplastic properties were characterized, revealing the intrinsic mechanisms of thermal deformation behavior. The results indicate that the best superplasticity is achieved at 460 °C. This is attributed to the smallest grain size, the weakest texture, and the relatively uniform distribution of the second phase at this temperature. The influence of strain rate on elongation at temperatures among 440 °C∼500 °C is not significant as the impact of strain rate is multifaceted. Meanwhile, the elongation can reach up to 367.7 ± 3.7 % at a strain rate of 0.0 1s−1, which exhibits the high strain rate superplasticity (HSRS). Under these conditions, the deformation of coarse-grained WE43 rare-earth magnesium alloy is controlled by grain boundary sliding (GBS) and solute drag dislocation creep. Furthermore, the GBS involves deformation coordination mechanisms such as grain boundary diffusion, lattice diffusion, dislocation climbing, and dynamic recrystallization accommodation mechanisms.

Influence of laser power and scanning speed on microstructure evolutions and mechanical properties of the SLM fabricated Al-Mg-Mn-Sc-Zr alloy

The Al-Mg-Mn-Sc-Zr alloy is fabricated by selective laser melting (SLM). The influence of laser power and scanning speed on microstructure evolutions and mechanical properties is studied in this research. Results indicate that increasing laser power can refine grain structures and reduce anisotropy on the printing surface. However, the increase in laser power will enhance the residual stress inside the alloy, leading to a decrease in elongation. The scanning speed affects the molten pool energy input and cooling rate. When the scanning speed is between 750mm/s-1250mm/s, the alloy achieves a good grain refinement effect and weak texture strength. In addition, there exists a large number of nano-scaled Al3(Sc,Zr) particles precipitated during solidification and the subsequent annealing process, which can significantly enhance yield strength of the alloy. Overall, the Al-Mg-Mn-Sc-Zr alloy has a wide SLM forming window. When the laser power ranges from 200W to 250W, the scanning speed ranges from 750mm/s to 1250mm/s, and the volume energy density ranges from 80J/mm3 to 130J/mm3, the Al-Mg-Mn-Sc-Zr alloy can obtain good formability and mechanical property.

Solidification and crystallographic texture modeling of laser powder bed fusion Ti-6Al-4V using finite difference-monte carlo method

Laser powder bed fusion (LPBF) additive manufacturing makes near-net-shaped parts with reduced material cost and time, rising as a promising technology to fabricate Ti-6Al-4 V, a widely used titanium alloy in aerospace and medical industries. However, LPBF Ti-6Al-4 V parts produced with 67° rotation between layers, a scan strategy commonly used to reduce microstructure and property inhomogeneity, have varying grain morphologies and weak crystallographic textures that change depending on processing parameters. This study predicts LPBF Ti-6Al-4 V solidification at three energy levels using a finite difference-Monte Carlo method and validates the simulations with large-area electron backscatter diffraction (EBSD) scans. The developed model accurately shows that a 〈001〉 texture forms at low energy and a 〈111〉 texture occurs at higher energies parallel to the build direction but with a lower strength than the textures observed from EBSD. A validated and well-established method of combining spatial correlation and general spherical harmonics representation of texture is developed to calculate a difference score between simulations and experiments. The quantitative comparison enables effective fine-tuning of nucleation density (N0) input, which shows a nonlinear relationship with increasing energy level. Future improvements in texture prediction code and a more comprehensive study of N0 with different energy levels will further advance the optimization of LPBF Ti-6Al-4 V components. These developments contribute a novel understanding of crystallographic texture formation in LPBF Ti-6Al-4 V, the development of robust model validation and calibration pipeline methodologies, and provide a platform for mechanical property prediction and process parameter optimization.

Unusual microstructure and texture transition during hot compression in an extruded Mg-Gd-Zr alloy with fiber texture

In magnesium (Mg) alloys with high rare earth content, slip modes and twinning behaviors are quite different from that in traditional Mg alloys. Deformation mechanisms, i.e., {11−21} twinning and non-basal slips, can activate during deformation process even at room temperature (RT) and contribute effectively to microstructure and texture transition. In order to figure out the influence of temperature on these deformation mechanisms and resultant microstructure and texture transition, compression tests were conducted on an extruded Mg-17.5Gd-Zr (wt%) alloy with <0001> fiber texture at temperature range of RT-450 °C. During compression, both {10−12} and {11−21} twinning behaviors can be governed by Schmid law at RT-350 °C and act as main contributors to texture transition. When the compression tests were carried out above 400 °C, twinning behaviors almost vanished and dynamic recrystallization (DRX) preferred activating within grains with the orientation of <10–10>//compression direction. DRX changed from continuous DRX to discontinuous DRX with the temperature increasing, which can be attributed to the temperature increasing and resultant elimination of sessile structure induced by cross-slip on basal plane. DRXed grains show weak texture and the texture mainly result from the properties of several near coincident site lattice boundaries.

High-Precision Disparity Estimation for Lunar Scene Using Optimized Census Transform and Superpixel Refinement

High-precision lunar scene 3D data are essential for lunar exploration and the construction of scientific research stations. Currently, most existing data from orbital imagery offers resolutions up to 0.5–2 m, which is inadequate for tasks requiring centimeter-level precision. To overcome this, our research focuses on using in situ stereo vision systems for finer 3D reconstructions directly from the lunar surface. However, the scarcity and homogeneity of available lunar surface stereo datasets, combined with the Moon’s unique conditions—such as variable lighting from low albedo, sparse surface textures, and extensive shadow occlusions—pose significant challenges to the effectiveness of traditional stereo matching techniques. To address the dataset gap, we propose a method using Unreal Engine 4 (UE4) for high-fidelity physical simulation of lunar surface scenes, generating high-resolution images under realistic and challenging conditions. Additionally, we propose an optimized cost calculation method based on Census transform and color intensity fusion, along with a multi-level super-pixel disparity optimization, to improve matching accuracy under harsh lunar conditions. Experimental results demonstrate that the proposed method exhibits exceptional robustness and accuracy in our soon-to-be-released multi-scene lunar dataset, effectively addressing issues related to special lighting conditions, weak textures, and shadow occlusion, ultimately enhancing disparity estimation accuracy.

Cascade contour-enhanced panoptic segmentation for robotic vision perception.

Panoptic segmentation plays a crucial role in enabling robots to comprehend their surroundings, providing fine-grained scene understanding information for robots' intelligent tasks. Although existing methods have made some progress, they are prone to fail in areas with weak textures, small objects, etc. Inspired by biological vision research, we propose a cascaded contour-enhanced panoptic segmentation network called CCPSNet, attempting to enhance the discriminability of instances through structural knowledge. To acquire the scene structure, a cascade contour detection stream is designed, which extracts comprehensive scene contours using channel regulation structural perception module and coarse-to-fine cascade strategy. Furthermore, the contour-guided multi-scale feature enhancement stream is developed to boost the discrimination ability for small objects and weak textures. The stream integrates contour information and multi-scale context features through structural-aware feature modulation module and inverse aggregation technique. Experimental results show that our method improves accuracy on the Cityscapes (61.2 PQ) and COCO (43.5 PQ) datasets while also demonstrating robustness in challenging simulated real-world complex scenarios faced by robots, such as dirty cameras and rainy conditions. The proposed network promises to help the robot perceive the real scene. In future work, an unsupervised training strategy for the network could be explored to reduce the training cost.

Investigating the combined influence of rolling, ECAP processes, and intermediate annealing on mechanical and microstructural properties of beryllium copper alloy 25

A beryllium copper alloy 25 underwent a series of processing steps involving rolling, equal-channel angular pressing (ECAP), and subsequent annealing. This study delved into the combined effects of these processes on the microstructural evolution and mechanical properties of the deformed beryllium copper alloy 25. The investigation utilized optical microscopy, scanning electron microscopy, transmission electron microscopy, room temperature Vickers hardness testing, and tensile testing. The findings reveal a notable enhancement in the strength of the beryllium copper alloy 25 while preserving its ductility after subjecting it to six ECAP passes followed by annealing at 210 °C for 20 min, applied to the rolled sample. Initially, an increase in number of ECAP passes resulted in a gradual reduction in grain size and a weakening of the alloy's texture. This led to an increase in ultimate tensile strength up to 333.5% without reducing in percentage elongation. Notably, after six ECAP passes, the average grain size decreased from 48 µm to less than 1 µm, yielding exceptional comprehensive mechanical properties with significantly improved strength and plasticity. The resultant material exhibits promising potential for fabrication into bars and plates for a wide range of applications in aerospace and marine industries.

Improved weak texture multi-view 3D reconstruction algorithm based on deformable convolutions networks

Improved weak texture multi-view 3D reconstruction algorithm based on deformable convolutions networks

Unveiling the mechanical and microstructural properties of SiC reinforced aluminum wires recycled from scraps by friction stir extrusion

Friction Stir Extrusion (FSE) has been proven as an effective solid-state process to directly recycle metal chips into high-quality wires/rods/tubes. However, the demand for Al-based composite wires with enhanced properties is substantial, and achieving a uniform distribution of the strengthening phase within the composite wire by establishing a robust metal/ceramic interface remains a significant challenge. In this study, AA6082 Aluminum alloy wires reinforced with 12.5 vol% SiC particles, exhibiting homogeneous particle distribution and superior mechanical properties, were successfully produced through the FSE technique. The investigation focused on examining the influence of processing parameters and the addition of SiC reinforcement on the microstructure and mechanical characteristics of the extruded wires. Scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), together with microhardness, bending, and tensile tests, were used to comprehensively analyze the resulting properties. The findings demonstrate a substantial enhancement in the wires' mechanical properties due to the SiC particles. Both tool rotation and tool force were varied during the experimental campaign. Notably, the reduction in porosity and grain refinement resulted in a 12.78 % increase in tensile strength and an 18.6 % improvement in microhardness compared to Al 6082 alloy extruded wires. Grain orientation analysis revealed a fully recrystallized microstructure with a weak texture. Furthermore, the study evaluated power consumption and surface roughness while assessing the feasibility of deposition, thereby highlighting the potential application of this technique in advanced additive manufacturing processes.

Significant ductility enhancement for high thermal conductivity Mg-2Sn-2.3La alloy via Zn addition

Herein, we introduced a trace amount of Zn into a high-thermal conductivity (HTC) MgSnLa-based alloy and prepared HTC MgSnLaZn alloy with large ductility as well as high strength by a carefully-designed rolling and annealing process. The elongation and strength of the as-annealed MgSnLaZn alloy are 28 % and 215 MPa, respectively, which are increased by 60 % and 16.9 %, respectively, compared with the MgSnLa-based alloy. Addition of Zn converts the Mg12La phase into the τ1 phase and partly dissolved into the matrix, resulting in slight decrease in electrical conductivity (about 3.5 W/(m-K)), but effectively enhancing the tensile properties. The purity of matrix and the fine dispersed precipitation phases ensure that the electrical and thermal conductivity is close to that of pure magnesium. Non-basal texture characteristics and weak texture intensity are the key factors for improvement in ductility.

A novel strategy to achieve uniform ultrafine grains in Mg-Al-Sn-Ca alloy via pre-twinning combined with differential-thermal asymmetric extrusion

Obtaining fine grains with weak textures is an efficacious way of simultaneously improving the strength and ductility of magnesium (Mg) alloys. In this paper, an Mg-Al-Sn-Ca alloy with uniformly ultrafine grains and a weak texture has been prepared via pre-twinning followed by differential-thermal asymmetric extrusion (DAE). The alloy exhibits good strength and ductility (ultimate tensile strength: ∼381 MPa; elongation: ∼22 %). The results show that {102} tensile twins significantly promote dynamic recrystallization (DRX) during DAE, which beneficial for the formation of uniform fine grain structure and weak bimodal texture. This research provides valuable insights and methods for tailoring excellent mechanical properties of Mg alloys, facilitating their practical application in various engineering scenarios.