Crystallographic Texture Research Articles

Effect of keyhole and lack-of-fusion pores on the anisotropic microstructure and mechanical properties of PBF-LB/M-produced CuCrZr alloy

Abstract Due to the high reflectance and heat conductivity of copper and its alloys, the processing window for laser-based powder bed fusion (PBF-LB/M) processing of high-density copper components fundamentally overlaps with conduction and keyhole melting zones, resulting in the emergence of certain pores in the structure of printed parts. The present research aims to study how the development of process-induced lack-of-fusion or keyhole porosities during the PBF-LB/M process can affect the anisotropic microstructure and mechanical properties of the produced copper alloys. For this purpose, several samples were produced utilizing a similar CuCrZr-feedstock composition but varied process parameters from different areas of the PBF-LB/M processing window, specifically at laser powers of 300 W and 380 W which define the boarders of the conduction and keyhole regimes. X-ray computed tomography (XCT) revealed that the 300-W and 380-W samples achieved relative densities of 98.88% and 99.99%, respectively, with elongated lack-of-fusion pores forming at 300 W and semi-spherical keyhole pores at 380 W. Microstructural analyses employing scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) demonstrated strong anisotropy in different build directions of the samples, owing to the growth of long columnar grains with intense < 101 > orientation along the build directions. Here, the emergence of different types of pores can cause competition between the epitaxial growth of columnar grains and the heterogeneous nucleation of new grains on the layers’ interfaces, thereby significantly varying the grain size, preferred orientation, crystallographic texture, and microstructural anisotropy of the samples. Furthermore, compression tests and nanoindentation measurements of the printed alloys in the longitudinal and transverse directions revealed that the 300 W and 380 W samples exhibited compressive strength anisotropies of 0.061 and 0.072, and average nanoindentation hardness values of 1.3 GPa and 1.5 GPa, respectively. The orientation of elongated lack-of-fusion porosities perpendicular to the loading axis was identified as the most damaging factor, significantly reducing mechanical performance compared to the uniformly distributed keyhole pores.

Elucidating the role of combined latent hardening due to slip-slip and slip-twin interaction for modeling the evolution of crystallographic texture in high nitrogen steels

Elucidating the role of combined latent hardening due to slip-slip and slip-twin interaction for modeling the evolution of crystallographic texture in high nitrogen steels

Simulation of Crystallographic Texture After High Temperature Axisymmetric Extrusion of Aluminum Alloys

Simulation of Crystallographic Texture After High Temperature Axisymmetric Extrusion of Aluminum Alloys

Microstructure characteristics and crystallographic orientation in dissimilar friction stir welding

This study examines the microstructural properties such as grain structure, grain boundary misorientation, and crystallographic texture of friction stir welding (FSW) joints under two cooling media (air and water cooling). The microstructural evolution of FSW joints was characterized using light and electron microscopy techniques. Specifically in electron microscopy, inverse pole figure maps, pole figures, and orientation distribution functions were evaluated for both conditions of FSW joints using Electron Back Scattered Diffraction (EBSD). The water-cooling FSW (WCFSW) joint exhibited the smallest grain sizes at the stir zone (SZ) location compared to the corresponding condition in the air-cooling FSW (ACFSW) joint. EBSD analysis revealed that grain size in the SZ was about 7.6 µm in the ACFSW joint and further refined to 3.2 µm in the WCFSW joint. The misorientation angle distribution of water cooling conditions generated high-angle grain boundaries. The main texture components observed in the FSW samples were Brass [{110} < 112>] and Goss [{110} < 001>]. Additionally, Orientation Distribution Function (ODF) analysis found a higher texture intensity in water-cooled joints than in air-cooled joints. The WCFSW joint also had higher ultimate tensile strength values and a faster strain hardening rate. This is because the grains were smaller, more dislocations were created, and suitable texture components and intensity were favorable.

Surface Integrity and Machining Mechanism of Al 7050 Induced by Multi-Physical Field Coupling in High-Speed Machining

Improving the surface quality and controlling the microstructure evolution of difficult-to-cut materials are always challenges in high-speed machining (HSM). In this paper, surface topography, defects and roughness are assessed to characterize the surface features of 7050 aluminum alloy (Al 7050) under HSM conditions characterized by high temperature, strain and strain rate. Based on multi-physical field coupling, the mechanism of microstructure evolution of Al 7050 is investigated in HSM. The results indicate that the surface morphology and roughness of Al7050 during HSM are optimal at fz = 0.025 mm/z, and the formation of surface defects (adherent chips, cavities, microcracks, material compression and tearing) in HSM is mainly affected by thermo-mechanical coupling. Significant differences are observed in the microstructure of different machined subsurfaces by electron backscatter diffraction (EBSD) technology, and high cutting speeds and high feed rates contributed to recrystallization. The crystallographic texture types on machined subsurface are mainly {110}<112> Brass texture, {001}<100> Cube texture, {123}<634> S texture and {124}<112> R texture, and the crystallographic texture type and intensity are significantly affected by multi-physical field coupling. The elastic–plastic deformation and microstructural evolution of Al7050 alloy during the HSM process are mainly influenced by the coupling effects of multiple physical fields (stress–strain field and thermo-mechanical coupling field). This study reveals the internal mechanism of multi-physical field coupling in HSM and provides valuable enlightenment for the control of microstructure evolution of difficult-to-cut materials in HSM.

Evaluation of microstructure, crystallographic texture, crystal orientation, grain boundary characteristics, and mechanical characteristics of dissimilar joints of ASTM A240 and alloy 625 in different welding techniques for high temperature applications

Evaluation of microstructure, crystallographic texture, crystal orientation, grain boundary characteristics, and mechanical characteristics of dissimilar joints of ASTM A240 and alloy 625 in different welding techniques for high temperature applications

Effect of crystallographic texture on the anisotropy of fracture toughness in as-forged Ti-45Al-7Nb-0.4W-0.1B intermetallics

Effect of crystallographic texture on the anisotropy of fracture toughness in as-forged Ti-45Al-7Nb-0.4W-0.1B intermetallics

Correlating crystallographic texture with anisotropic properties and sheet metal forming of aluminium alloys

Correlating crystallographic texture with anisotropic properties and sheet metal forming of aluminium alloys

Structural-phase transformations and crystallographic texture in commercial Ti–6Al–4V alloy with globular morphology of α-phase grains: the rolling plane

The commercial Ti–6Al–4V alloy was obtained in an almost single-phase state, formed by finely dispersed globular α-grains with an average size of 12 μm, using thermomechanical processing, including hot rolling. The microtexture and structure of the alloy were studied using X-ray diffractometry and transmission and scanning electron microscopy, including orientation microscopy. It is found that for α-grains the Burgers orientation relationships are satisfied, and twin orientations are ensured in the rolling plane. A significant scattering of the crystallographic orientations of α-grains relative to each other (up to 10°–15°) is established for each group of close Burgers orientations as a result of plastic deformation by rolling at high temperatures. Clusters of microtexture regions in the layered microstructure of grains and the formation mechanisms and mutual crystallographic misorientations of microtexture regions and grains in the alloy have been identified.

Microstructural, Mechanical, and Tribological Properties of Selective Laser Melted Inconel 718 Alloy: The Influences of Heat Treatment

The present study investigates the microstructural, mechanical, and tribological properties of Inconel 718 alloy produced by selective laser melting (SLM) in relation to heat treatment. The SLM-processed samples received a two-step heat treatment: solutionizing at 1065 °C for 1 h, followed by double aging at 720 °C for 8 h and 620 °C for 6 h. The as-built sample exhibited a grain structure mostly characterized by fine Laves phases, while the hardening phases γ′ ((Ni3 (Al, Ti)) and γ″ (Ni3Nb) precipitated during the heat treatment. Following heat treatment, a transformation in crystallographic texture and dislocation density occurred, yielding a random texture and reduced dislocation density, particularly in the XZ direction, attributed to the formation of new grains via recrystallization in the microstructure. The grain size in the XY plane decreased following heat treatment, whereas the texture in the <001> direction remained unaffected. The heat-treated samples had significantly higher tensile strength (1330 MPa vs. 960 MPa) and hardness (530 HV vs. 340 HV) relative to the as-built samples. The wear resistance of heat-treated samples surpassed that of the as-built sample due to enhanced mechanical properties resulting from the fine and dispersed γ′ and γ″ precipitates in the microstructure with heat treatment.

Crystallographic texture before and after post weld heat treatment of high-frequency electric resistance welded API X65 linepipe

The microstructure and crystallographic textures of API X65 grade linepipe steel were studied in the base metal, the weld interface after high-frequency electric resistance welding (HF-ERW), and the weld interface following post-weld heat treatment (PWHT). Optical microscopy, scanning electron microscopy (SEM), and electron-backscattered diffraction (EBSD) were used to study the microstructure and texture evolution and correlated with Charpy V-notch impact toughness. The Charpy values were 172.9 ± 5.2 J for the base metal, 7.5 ± 1.6 J for the as-welded weld interface, and 69 ± 24 J after PWHT, with the latter still significantly lower than the base metal. Base metal showed a low fraction of low-indexed cleavage planes at about 9% and major texture components were (113)[110], (112)[110], and (332)[113]. In the as-welded condition, major intensities of rotated Cube (001)[110] and Goss (110)[001] texture components were observed near the weld interface. Although PWHT reduced the texture intensities, rotated Cube and Goss components were still observed. The fraction of cleavage planes was about 44% for the as-welded and about 30% for the PWHT-ed weld interface. Clearly, PWHT has reduced but not eliminated the detrimental rotated Cube and Goss textures at the weld interface. These detrimental textures likely have contributed to the low Charpy toughness after welding and continuing after PWHT.

High Coercivity and Strong [00l] Crystallographic Texture in Sm(CoFeCuZr)7.4 Nanoflakes Prepared by Surfactant‐Assisted Ball Milling

Sm(Co0.61Fe0.21Cu0.13Zr0.05)7.4 nanoflakes are prepared by surfactant‐assisted ball milling from annealed ingots, and the ingots are synthesized by the arc‐melting process. The X‐ray diffraction (XRD) patterns of nanoflakes exhibit two hard magnetic phases: Sm2Co17 is the primary hard phase, which provides high saturation magnetization, and SmCo5 acts as a minor hard phase, presumably impeding the movement of magnetic domain walls, thereby increasing intrinsic coercivity. The high coercivity value of 7.2 kOe is achieved after 0.5 h ball milling. In addition, the XRD patterns of nanoflakes at different milling times show a strong [00l] crystallographic texture after the magnetic alignment. A remanence value of 1.03 T and a maximum energy product of 123 kJ m−3 achieve in 0.5 h milled nanoflakes. The aligned nanoflakes show strong anisotropic behavior with a degree of anisotropy value of 0.81. Henkel plots indicate the strong exchange coupling interaction in nanoflakes milled for 0.5 h. Based on the analysis of temperature‐dependent hysteresis loops and initial magnetization curves, the coercivity is controlled by the pinning of domain wall movement and the nucleation of the reverse domains.

Classical View on Nonclassical Crystal Growth in a Biological Setting.

Crystallization by amorphous particle attachment, a nonclassical crystal growth mode, is prevalent in minerals formed by living tissues. It allows the organism to intervene at every step of crystal growth, i.e., particle formation, stabilization, accretion, and crystallization, and thus to orchestrate biomineral morphogenesis and crystallographic texturing; all toward achieving a required functionality for the organism. Therefore, significant effort is aimed at achieving similar control and crystal growth tunability through bioinspired and biomimetic synthetic means. This Perspective examines the driving forces and the kinetics of crystallization by amorphous particle attachment in a biological setting, and through an analogy to classical molecule-by-molecule crystallization, it establishes distinct crystal growth mechanisms. It underlines the role of physics and chemistry of materials in the "Growth and Form" of biogenic minerals.

Quantitative Indicators of Microstructure and Texture Heterogeneity in Polycrystalline System.

The microstructural features of polycrystals determine numerous properties, whereas the evolution of crystallographic texture is responsible for the anisotropy of particular properties. Therefore, it is of crucial importance to find proper quantitative indicators, which reflect the nature of microstructure and texture characteristics. This is partially performed by the assessment of the average grain size and texture intensity that provide basic information on the microstructural features evolved; however, often, the basic quantitative indicators are not capable of revealing the complete microstructural state especially when the system is highly heterogeneous. This contribution presents various methods to assess the degree of microstructural heterogeneity, while the crystallographic aspect of microstructure evolution is characterized by several indicators of texture heterogeneity. Numerous synthetic microstructures with normal, lognormal, and bimodal grain size distributions as well as their combinations are analyzed to evaluate the applicability of the methods presented in this study. The quantitative indicators described in the frame of this contribution are likewise tested on experimentally observed microstructures. It is shown that the derived coefficients of microstructure heterogeneity correlate well with the standard deviation in grain size distribution, Gini, and Hoover coefficients, while the quantitative measures of texture heterogeneity are capable of revealing hidden aspects of microstructure evolution.

Surface Characteristics and Crystallographic Texture Evolution of Aviation Aluminum Alloy in High-Speed Machining Based on Visco-Plastic Self-Consistent Model

The purpose is to investigate the surface characteristics and crystallographic texture evolution of aviation aluminum alloy during high-speed machining (HSM). The influence mechanism of machining parameters on the surface quality of Al 7050 is explored through HSM experiments, and the distribution of cutting temperature, equivalent stress and strain, and the variation trend of variables in the deformation zone on the path is analyzed by finite element (FE) simulation. Combining FE simulation and polycrystalline plasticity theory, a visco-plastic self- consistent (VPSC) model is established to simulate the crystal texture evolution in the machined surface layer, and the validity of the constructed model is confirmed by dynamic impact and EBSD results. The results show that the high-speed machined surface displays tool feed marks, apophysis, cavities, side flow bands and adhered chip debris. The overall trend of temperature and equivalent stress on the path shows a “spoon-like” distribution and an “M-like” distribution, respectively. The cutting temperature, equivalent stress and strain increase in relation to three cutting factors, where the cutting temperature and equivalent stress increase by 3% and 2.9%, respectively. VPSC simulations show the textures of {001}[Formula: see text]100[Formula: see text]Cube, {123}[Formula: see text]634[Formula: see text]S, {110}[Formula: see text]112[Formula: see text]Brass, and {112}[Formula: see text]110[Formula: see text]R-Copper which are present on the machined surfaces, and high feed rate and cutting speed enhance and weaken the strength of the {123}[Formula: see text]634[Formula: see text]S and {001}[Formula: see text]100[Formula: see text]Cube textures. The difference in texture maximum density under different machining parameters is 34%, and the type and intensity of crystal texture are profoundly influenced by the coupling effect of heating/force load, stress, and strain.

Tribological and mechanical behavior of AL 2014 aluminum alloy influenced by microstructure and texture evolution after equal channel angular processing

In the present study, the impact of microstructure and texture evolution on the wear and mechanical behavior of equal channel angular pressing (ECAP) of Al 2014 was examined. The average grain size of Al 2014 decreased dramatically from 101 to 6.5 microns after ECAP passes. The distribution of grain boundaries and crystallographic texture changed due to this grain refinement, significantly improving the wear and mechanical properties of the processed alloy. The enhanced wear resistance seen after ECAP resulted from low-angle boundaries (LABs) preventing fracture propagation, according to the electron backscatter diffraction (EBSD) analysis. Additionally, a notable change in texture was observed after ECAP; the initial S-rolling texture of the material, in its as-received condition, transformed into distorted Copper and A-type textures, indicating the complex strain conditions induced by the ECAP process. The ability of ECAP to improve the material's suitability for high-wear resistance applications was further demonstrated by tribological tests, which showed that the ECAP-processed Al 2014 alloy had noticeably lower wear rates than its as-received counterpart. Similarly, the mechanical results show that ECAP significantly improved the hardness and tensile characteristics.

Wire arc additive manufacturing of Ni Fe alloy/ductile cast iron bimetallic structure; Phase transformations, microstructure and crystallographic texture

Wire arc additive manufacturing of Ni Fe alloy/ductile cast iron bimetallic structure; Phase transformations, microstructure and crystallographic texture

Microstructural characteristics of hydrogen-exposed P355NH steel and welded joints

It is known that microstructure of materials, such as material structure, grain size, orientation, crystallographic texture and dislocation density, change the mechanism and intensity of hydrogen diffusion, contribute to an increase or decrease in solubility, which significantly changes the mechanical properties of steels and leads to brittleness. In the present study, the microstructure of welded joints of steel P355NH, a typical material grade in domestic transmission lines, and GMAW and hybrid GTAW /GMAW welded joints were investigated and exposed to high pressure pure hydrogen with exposure times of 41 and 92 days. The investigations were carried out to find out the characteristic microstructural details of the base material and welded joints, and the mechanical property changes that can be observed, which can be used to infer the hydrogen susceptibility of both the base material and the welded joints.

Wire arc additive manufacturing of Ni Fe alloy/ductile cast iron bimetallic structure; phase transformations, microstructure and crystallographic texture

Wire arc additive manufacturing of Ni Fe alloy/ductile cast iron bimetallic structure; phase transformations, microstructure and crystallographic texture

The development of crystallographic texture during porthole die extrusion of Al-Mg-Si alloys

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.