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High-performance potassium-sodium niobate lead-free piezoelectric ceramics based on polymorphic phase boundary and crystallographic texture
摘要： Lead-free piezoelectric ceramics are urgently needed in the field of electromechanical conversion devices due to the restriction on the use of lead-based ceramics. In this study, the polymorphic phase boundary (PPB) were tuned by incorporating different concentration of (Bi0.5K0.5)HfO3 into the matrix (K0.5Na0.5)(Nb0.965Sb0.035)O3-CaZrO3, and the <00l>c crystallographic texture was realized by templated grain growth method. The maximal d33 (~550 pC/N) and kp (~72%) were achieved in the <00l>c textured ceramics with composition around rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary. It is proposed that the enhanced piezoelectricity should be ascribed to several combined effects, which primarily contain the R-O-T phase boundary facilitating polarization rotation, the crystallographic orientation induced intrinsic piezoelectric anisotropy, electric-field-induced lattice distortion and phase transitions, and NaNbO3 seed-crystal-driven nanodomain structures. This work provides an effective solution to enhance piezoelectric properties by simultaneous tailoring polymorphic phase boundary and using crystallographic texture in potassium-sodium niobate based piezoelectric ceramics. We believe that the simple solution and design principle can also be applied to other piezoelectric ceramic systems, no matter lead-based or lead-free.
关键词： polymorphic phase boundary,piezoelectricity,potassium-sodium niobate,crystallographic texture
更新于2025-11-14 17:28:48
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Effects of laser surface melting on crystallographic texture, microstructure, elastic modulus and hardness of Tia??30Nba??4Sn alloy
摘要： The biocompatibility of orthopedic implants is closely related to their elastic modulus and surface properties. The objective of this study was to determine the effects of cold rolling, recrystallization and laser surface melting (LSM) on the microstructure and mechanical properties of a biphase (α″+β) Ti?30Nb?4Sn alloy. X-ray diffraction (XRD) texture analysis of the cold-rolled substrate revealed the [302]α″//ND texture component, while analysis of the recrystallized substrate showed the [302]α″//ND and [110]α″//ND components. The β-phase texture could not be directly measured by XRD, but the presence of the [111]β//ND texture component was successfully predicted by considering the orientation relationship between the α″ and β phases. Nanoindentation measurements showed that the elastic modulus of the cold-rolled substrate (63 GPa) was lower than that of the recrystallized substrate (74 GPa). Based on the available literature and the results presented here, it is suggested that this difference is caused by the introduction of crystal defects during cold deformation. The combined nanoindentation/EBSD analysis showed that the nanoindentation results are not affected by crystal orientation. LSM of the deformed alloy produced changes in hardness, elastic modulus and crystallographic texture similar to those produced by recrystallization heat treatment, creating a stiffness gradient between surface and substrate.
关键词： laser surface melting,stiffness-graded material,crystallographic texture,cold rolling,titanium alloy,recrystallization
更新于2025-09-23 15:21:01
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Crystallographic Orientation Control of 316L Austenitic Stainless Steel via Selective Laser Melting
摘要： In recent years, additive manufacturing has attracted attention as a technology that enables control of the crystallographic texture of metallic materials. We achieved successful control of the crystallographic texture of 316L austenitic stainless steel using selective laser melting (SLM). Three distinguished textures were achieved by changing the laser scan speed, namely: the single crystalline-like texture with {001} orientation in the build direction, the crystallographic lamellar texture in which two kinds of grains with {011} and {001} orientations in the build direction are alternately stacked, and polycrystalline with relatively random orientation. The melt pool shape and the solidification behavior (thermal gradient and migration velocity of solid/liquid interface) in a melt pool could be important controlling factors for the evolution of the crystallographic texture under the SLM process.
关键词： anisotropy,crystallographic texture,metal additive manufacturing (AM),selective laser melting (SLM),melt pool
更新于2025-09-23 15:19:57
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Single-crystalline-like stainless steel 316L with different geometries fabricated by laser powder bed fusion
摘要： In this study, we explored the feasibility of fabricating single-crystalline or single-crystalline-like stainless steel 316L (SS316L) with different geometries (thin struts, cubes, walls and a simulated pump impeller) using laser powder bed fusion (LPBF). The LPBF-fabricated SS316L thin struts possessed a single-crystalline core featuring a ?110? ∥ building direction (BD) crystallographic texture. The cubes, walls and the pump impeller preserved this ?110? ∥ BD texture and also exhibited a well-defined single-crystalline-like {110}?001? Goss texture. Cellular sub-grain structures with their primary dendrite arm spacing (PDAS) values smaller than 1 μm were discovered in all the samples with their growth directions showing a 45° angular deviation from the BD. Nanoscale precipitates and dislocations were also found in the cellular sub-grain structures of the thin struts. The mechanical properties of different geometries (the thin struts, the walls, and the simulated pump impeller) were studied and compared. The anisotropic mechanical responses of the walls and the simulated pump impeller were correlated with their crystallographic textures.
关键词： Single crystal,Geometries,Crystallographic texture,Laser powder bed fusion,Mechanical properties,Stainless steel 316L
更新于2025-09-23 15:19:57
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Microstructurea??Texturea??Mechanical Property Relationship in Alloys Produced by Additive Manufacturing Following Selective Laser Melting (SLM) Technique
摘要： Additively manufactured alloys produced by selective laser melting (SLM) exhibit different microstructure, texture and mechanical properties compared to their conventionally processed counterparts. The reason for this difference has been attributed to unique conditions that are met during processing through SLM. The differences are specific to the alloy system. Most influencing variable of SLM processing has been found to be the scanning strategy which comprises interlayer hatch rotation, build orientation, printing pattern (unidirectional, meander or checker board), etc. These variants lead to alteration of microstructure and crystallographic texture. Among the properties, yield strength of SLM-processed alloys has been found to be higher compared to their conventionally processed counterparts, which has been attributed to the finer microstructure and high defect density resulting from the process. On the other hand, ductility is on the lower side due to voids and porosity. The texture of SLM-processed materials shows characteristic features, which is dependent on materials and processing strategies. This further influences the properties. This paper deals with the evolution of microstructure, texture and mechanical properties for selected alloy systems, namely the alloys of iron, aluminium, and titanium, which have been most extensively studied after SLM processing.
关键词： Mechanical properties,Crystallographic texture,Additive manufacturing,Microstructure,Selective laser melting
更新于2025-09-16 10:30:52
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Effects of laser additive manufacturing on microstructure and crystallographic texture of austenitic and martensitic stainless steels
摘要： Powder-fed laser additive manufacturing (LAM) based on directed energy deposition (DED) technology is used to produce S316-L austenitic, and S410-L martensitic stainless steel structures by 3D-printing through a layer-upon-layer fashion. The microstructural features and crystallographic textural components are studied via electron backscattering diffraction (EBSD) analysis, hardness indentation and tensile testing. The results are compared with commercial rolled sheets of austenitic and martensitic stainless steels. A well-developed <100> direction solidification texture (with a J-index of ~11.5) is observed for the austenitic structure produced by the LAM process, compared to a J-index of ~2.0 for the commercial austenitic rolled sheet. Such a texture in the LAM process is caused by equiaxed grain formation in the middle of each layer followed by columnar growth during layer-upon-layer deposition. A quite strong preferred orientation (J-index of 17.5) is noticed for martensitic steel developed by LAM. Large laths of martensite exhibit a dominant textural component of <011>//{111} in the α-phase, which is mainly controlled by transformation during layer-by-layer deposition. On the other hand, the martensitic commercial sheet consists of equiaxed grains without any preferred orientation or completely random orientations. In the case of the austenitic steel, mechanical properties such as tensile strength, hardness and ductility were severely deteriorated during the LAM deposition. A ductility loss of about 50% is recorded compared to the commercially rolled sheets that is attributed to the cast/solidified structure. However, LAM manufacturing of martensitic stainless steel structures leads to a considerably enhanced mechanical strength (more than double) at the expense of reduced ductility, because of martensitic phase transformations under higher cooling rates.
关键词： Directed energy deposition (DED),Laser additive manufacturing (LAM),Crystallographic texture,S316-L austenitic stainless steel,S410-L martensitic stainless steel
更新于2025-09-12 10:27:22