Search

The additive manufacturing of directionally solidified Ni-based superalloys remains a significant challenge due to the formation of stray equiaxed grains and their high susceptibility to cracking, particularly for high-volume γ´-type Ni-based superalloys. In this study, a novel strategy based on temperature field management was proposed to prevent hot cracking and control crystallographic texture during laser powder bed fusion (LPBF) of IN738LC superalloy. The influence of laser parameters and substrate preheating on crack density, melt pool morphology, and texture of IN738LC superalloy was investigated. The fluid dynamics and thermal behavior of melt pool was simulated using the discrete element model (DEM) and volume of fluid (VOF) method. The processing window for achieving defect-free IN738LC samples was established and was found to be highly affected by substrate preheating. Substrate preheating at 350 °C resulted in expanded processing window, with the volume energy density ranging from 42.9 to 62.5 J/mm³ without substrate preheating to 40–75 J/mm³. The enlarged processing window was achieved by reducing cracking susceptibility due to the reduced temperature gradient and cooling rate. A unique crystallographic lamellar microstructure (CLM), comprising a -oriented major layer and -oriented sub-layer along the building direction, was successfully achieved in the LPBF-processed IN738LC superalloy. The solidification conditions for obtaining such a CLM were discussed on the aspects of temperature gradient and solidification rate within the melt pool. This work provides new insights and methods for preparing crack-free γ´-Ni-based superalloys with specific textures, which is favorable for improving the high-temperature properties.

The paper covers the production, analysis of the microstructure, crystallographic texture and deformation mechanisms of the ultrafine-grained (UFG) Zn–1%Mg–1%Fe zinc alloy demonstrating unique physical and mechanical properties compared to its coarse-grained analogues. The zinc alloy with improved mechanical properties was developed in two stages. At the first stage, based on the analysis of literature data, an alloy with the following chemical composition was cast: Zn–1%Mg–1%Fe. Then, the alloy was subjected to high-pressure torsion (HPT) to improve mechanical properties, due to grain structure refinement, and implementation of dynamic strain aging. The conducted mechanical tensile tests of the samples and assessment of the alloy hardness, showed that HPT treatment leads to an increase in its tensile strength to 415 MPa, an increase in hardness to 144 HV, and an increase in ductility to 82 %. The obtained mechanical characteristics demonstrate the suitability of using the developed alloy in medicine, as some implants (stents) requiring high applied loads. To explain the reasons for the improvement of the mechanical properties of this alloy, the authors carried out comprehensive tests using microscopy and X-ray diffraction analysis. The microstructure analysis showed that during the formation of the ultrafine-grained structure, a phase transition is implemented according to the following scheme: Zneutectic + Mg2Zn11eutectic + FeZn13 → Znphase + Mg2Zn11phase + MgZn2particles + Znparticles. It was found that as a result of high pressure torsion in the main phases (Zn, Mg2Zn11), the grain structure is refined, the density of introduced defects increases, and a developed crystallographic texture consisting of basic, pyramidal, prismatic, and twin texture components is formed. The study showed that the stability of pyramidal, prismatic and twin texture components at the initial stages of high-pressure torsion, determines the level and anisotropy of the strength properties of this alloy. The relationship between the discovered structural features of the produced alloy and its unique mechanical properties is discussed.

The use of hollow aluminum extrusions in internal combustion engine and battery electric powered vehicles has increased significantly in recent years due to lightweighting considerations. It is of interest to understand the evolution of crystallographic texture from a through-process perspective, since the microstructure and texture of the material have a strong influence on plasticity in the final part. In this research, an Al-Mg-Si alloy with Mn and Cr additions to suppress recrystallization was halted mid-extrusion, and the in-die material was extracted for study. The evolution of textures along finite element method (FEM) predicted streamlines were characterized with electron backscatter diffraction (EBSD). Polycrystal plasticity modelling coupled with the FEM simulated deformation history was implemented to predict texture evolution. Streamlines passing near the center of the portholes exhibited axisymmetric double fiber textures, which rotated following the streamlines before shifting to plane strain textures near the die exit. Closer to the weld seam, shear textures developed. It was found that textures could be predicted for streamlines up to 1.4 mm away from the weld seam, where complex deformation modes, significant increase in strain and the possible intervention of alternative mechanisms such as recrystallization and non-octahedral slip inhibit the accuracy of texture prediction.

Laser powder bed fusion of metals (PBF-LB/M) is a pivotal additive manufacturing technique that enables the production of intricate components. In addition to enabling the production of complex shapes, it allows for a high degree of freedom in manipulating the microstructure. The present investigation explores the manipulation of the crystallographic texture in AISI 304L stainless steels via PBF-LB/M, due to the possibility of tailoring the secondary hardening phenomena. Neutron diffraction provides efficient texture assessment, while decision tree regression reveals the complex interplay between processing parameters and the resulting crystallographic textures. Our investigation identifies the optimal PBF-LB/M processing parameters for obtaining strong texture along the build and laser scan directions. Additionally, microstructural characterisation of selected samples reveals the complex solidification structures. By employing advanced characterisation techniques and machine learning, this work provides insights into achieving or avoiding specific crystallographic textures during PBF-LB/M processing of stainless steels or other materials.

The influence of anisotropy induced by the crystallographic texture on the elastocaloric cooling effect of rolled NiTi alloy was investigated. Cyclic tensile tests were conducted along various directions angles (θ) between the rolling direction (RD) and the transverse direction (TD). The results demonstrated that the dominant texture component of the material were {110} and {001}. With the presence of texture component {110} and {001}, the elastocaloric cooling effect of rolled NiTi alloy presented unusual anisotropy. The adiabatic temperature change ΔTadi is maximum in the θ = 0° direction (//RD) and minimum in the θ = 90° (//TD)direction. The material coefficient of performance COPmat and Carnot COP were also analyzed and evaluated. The maximum COPmat and Carnot COP obtained were 26.5 and 67%, respectively, indicating a remarkable balance between cooling capacity and efficiency. The present research shed light on optimizing the elastocaloric cooling effect by introducing crystallographic texture characteristic in rolled NiTi alloy.

Ferroelectric (FE) hafnium zirconium oxide (HZO) is an excellent candidate for data storage applications. However, it has some reliability limitations such as imprint and retention. Herein, we explore Al doping of HZO to overcome these limitations. FE behavior is tuned by the aluminum (Al) concentrations in the films and by annealing temperature. A correlation is done between electrical behavior, crystallographic texture, and FE phases determined by grazing-incidence X-ray diffraction (GIXRD) measurements. Reduced coercive field (2Ec) values and wake-up free HZO-based ferroelectrics are explored. We show the tunability of remanent polarization (2Pr) and 2Ec with respect to Al-doping concentration and anneal temperature, hence crystallographic texture.

This study aimed to provide a comprehensive understanding of how aging treatments (namely, HT1 and HT2) affect the microstructure, cracking behavior, and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) method. Although both aged samples demonstrated similar grain structure and recrystallization behavior according to the electron backscatter diffraction (EBSD) analysis, as well as the precipitation of bimodal γ′ phase and MC- and M23C6-type carbides, notable differences were observed in the size and morphology, particularly the γ′ phase. The HT1 sample displayed coarsened primary γ′ phase, with sizes reaching up to 2 μm and exhibiting varied morphologies, including irregular and cuboidal shapes. Additionally, this treatment led to the formation of some γ′-γ eutectic regions and plate-like η phase, along with the decomposition of MC-type carbides into M23C6-type carbides. In contrast, the HT2 sample displayed uniformly distributed spherical primary γ′ phase with sizes ranging from 70 to 120 nm, accompanied by very fine secondary γ′ phase. Furthermore, it was found that changes in both aged sample microstructures could result in the formation of strain-age cracks due to the γ′ phase formation and liquation cracks due to the partial remelting of lower melting point phases. The findings also revealed that with the application of aging treatments, the hardness of the as-fabricated sample (339.8 ± 3.4 HV) increased to 440.2 ± 5.6 HV and 508.1 ± 4.8 HV for the heat treatment of HT1 and HT2, respectively.

The elastic and plastic anisotropy of aluminium wrought alloys is largely controlled by the crystallographic texture of the material, which has developed during the preceding thermomechanical processing. Conversely, texture can be exploited to simulate anisotropic materials properties, typically with the help of crystal-plasticity simulations. The present paper summarizes the author's activities on using texture to simulate anisotropic materials behaviour with the help of the visco-plastic self-consistent (VPSC) scheme. Application possibilities include the prediction of in-plane anisotropy developing during uniaxial and plane strain tensile tests, earing during cup drawing of Al sheet products as well as polycrystal-plasticity driven prediction of input data used to calibrate phenomenological yield functions.Sheet metal forming is commonly simulated with the finite element method (FEM), where anisotropic properties are accounted for by suitable materials models. Notwithstanding that state-of-the-art phenomenological yield functions provide for a high flexibility sufficient to capture the anisotropy of strongly textured materials, the experimental determination of the required calibration parameters is tedious. Rather, the materials parameters needed to calibrate the yield function are derived in a pragmatic and computationally efficient approach with VPSC simulations from texture. The resulting multilevel modelling framework is evaluated against earing simulations which constitute a demanding proof-of-principle for consideration of the anisotropic materials response during FEM forming simulations.

Compositional and anatomical studies of silicified wood have been carried out extensively all around the world. The classification of silicified wood as such deals with all the forms and phases of silica that come under its umbrella. One such class of silicified wood is fossil wood with a high content of quartz, and there are very limited mentions of this category of fossilized wood. The examined wood belongs to gymnosperm and comes from the Upper Triassic deposits of Madagascar. A fresh approach to such samples is adopted by studying the crystallographic texture of the fossil wood to understand the orientation of the crystals replacing the organic matter within the sample. This work focuses on crystallographic texture analysis based on pole figures measured by X-ray diffraction. The intensity of the pole density maxima on the pole figures measured on the heartwood surface part of the analyzed samples is higher than that on the sapwood. This affirms that the crystallographic texture is sharper at the heartwood part compared to the sapwood. The X-ray tomography study, conducted to understand the difference in mineral distribution within the sample, reveals a greater X-ray absorbing phase on the sapwood of both samples. This is due to the concentration of iron compounds, which both replace the remaining conductive structures of the wood and fill the cavities inside them. We believe that this research on silicified wood is the first research work that encompasses crystallographic texture analysis with pole figures, an approach not previously undertaken in similar studies. We hope that our research can be useful in understanding the processes of replacement of organic matter by minerals. [ABSTRACT FROM AUTHOR]

Laser Powder Bed Fusion (L-PBF) has emerged as a leading additive manufacturing (AM) technique for manufacturing complex metal parts, with 316L stainless steel being favored for its exceptional corrosion resistance and mechanical properties. While previous studies have explored the effects of different scan strategies and build orientations on the microstructure and room temperature tensile properties of L-PBF printed 316L stainless steel, there is still a lack of a comprehensive predictive model that accurately captures the combined effects of these process parameters on the final crystallographic texture and tensile properties. This study presents a novel approach that establishes a direct correlation between process parameters, microstructure, and mechanical behavior by modeling the influence of scan strategy rotation angles and build orientations on the crystallographic texture of L-PBF-manufactured 316L stainless steel. To validate the model, a series of samples were fabricated using various scan strategy rotation angles and build orientations, enabling detailed microstructural analysis and mechanical testing. The findings demonstrate a direct relationship between the selected process parameters and the resulting mechanical properties, underscoring the importance of scan strategy and build orientation selection on mechanical response. Furthermore, our calibrated model exhibits high predictive accuracy as validated through a comparison with experimental data.