- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Effect of build geometry and orientation on microstructure and properties of additively manufactured 316L stainless steel by laser metal deposition
摘要： The effect of build geometry and orientation on the microstructure and mechanical properties of additively manufactured AISI 316L stainless steel was studied. For this an integrated laser metal deposition system was used to build two test blocks, Block 1 and Block 2, such that Block 1 had its longest dimension parallel to the build direction while Block 2 had its longest dimension perpendicular to the build direction. Samples with different orientations with respect to the build direction were extracted from the two blocks and characterized in detail. Block 1 was found to have a coarser defect-free microstructure, while Block 2 had a finer microstructure with extensive inter-track/layer defects. The yield strengths and tensile strengths of Block 2 samples were higher than Block 1 samples, but their strain hardening capacities and ductility values were lower. These differences in microstructure and mechanical properties were shown to be an outcome of the different build rates and consequent thermal histories of the two blocks. In order to explain the variation of yield strength with sample orientation, an alternate measure for grain size called “effective grain size” was introduced, which revealed the effect of grain orientation on the mean free path for dislocation motion and hence yield/flow stress. Variation of yield strength with the effective grain size was found to follow Hall-Petch behaviour.
关键词： Anisotropy,Additive Manufacturing,Grain Size,Tensile Behaviour,Orientation
更新于2025-11-28 14:24:20
-
Grain size evolution under different cooling rate in laser additive manufacturing of superalloy
摘要： The processing parameters in laser additive manufacturing have a crucial impact on solidification microstructure especially grain size, thus influencing the properties of the final products. In this paper, experiments were conducted to investigate the effects of processing parameters including scanning speed, laser power and powder feeding rate on grain size of the solidified track during laser metal deposition. A three-dimensional model considering heat transfer, phase change and Marangoni convection flow had also been developed to simulate the solidification parameters especially cooling rate (G × R) to illustrate the underlying mechanisms. The experimental and simulated results indicated that cooling rate increased and grain size decreased from 8.7 μm to 4.7 μm with the increase of scanning speed from 2 mm/s to 10 mm/s. Contrarily, cooling rate decreased and grain size increased with the increase of laser power and powder feeding rate. The numerical and experimental results provide the additive manufacturing process with the potential of microstructure control and performance optimization.
关键词： Grain size,Laser additive manufacturing,Superalloy,Solidification,Cooling rate
更新于2025-11-21 11:18:25
-
Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics
摘要： In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.
关键词： Dielectric properties,Grain size,X-ray diffraction,Optical properties,Sintering
更新于2025-11-21 11:18:25
-
Rapid synthesis of AlON powders by low temperature solid-state reaction
摘要： High synthesis temperatures and long soaking times are generally required to fabricate AlON powders, which can cause coarsening and aggregation of the powder. Solid-state reaction methods form AlON powders by a direct reaction of Al2O3 and AlN, enabling rapid synthesis of AlON powder at low temperatures. In this work, single phase AlON powders were fabricated by a solid-state reaction method using Al2O3 and AlN powders as raw materials. To lower the synthesis temperature and shorten the soaking time, the raw materials particle sizes and the homogeneity of the Al2O3/AlN mixture were investigated. The effects of AlN content, synthesis temperature, and soaking time on the synthesis of AlON powders were examined. When the AlN content was 27 mol %, single phase AlON powders were synthesized by calcining Al2O3/AlN mixture at 1680 °C for 20 min. After ball-milling at 250 rpm for 24 h, the synthesized AlON powder was ground into a single phase fine AlON powder with an average particle diameter of 320 nm, a narrow size distribution, and good dispersibility. Transparent AlON ceramics with dimensions of Φ100 mm × 1 mm were fabricated by pressureless sintering the produced fine AlON powder.
关键词： B.Grain size,Aluminum oxynitride,A. Powders: solid-state reaction
更新于2025-11-19 16:56:35
-
Characterisation of AlN nano thin films prepared by PLD
摘要： Aluminium nitride (AlN) nano thin films have been prepared by pulsed laser deposition (PLD) in this paper. The microstructure and grain size of the nano thin films were characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the PLD conditions such as laser fluence, ambient pressure and substrate temperature influence the thickness, morphology and grain size of the nano thin films obviously, i.e. the surface of the nano thin films becomes rough while the grain size increases with increasing the laser fluence, ambient pressure and substrate temperature. In addition, there exists a preferred orientation growth in the thin films.
关键词： microstructure,pulsed laser deposition (PLD),aluminium nitride,grain size,Nano thin films
更新于2025-09-23 15:22:29
-
Using soft polymer template engineering of mesoporous TiO <sub/>2</sub> scaffolds to increase perovskite grain size and solar cell efficiency
摘要： The mesoporous (meso)-TiO2 layer is a key component of high efficiency perovskite solar cells (PSCs). Herein, pore size controllable meso-TiO2 layers are prepared using spin coating of commercial TiO2 nanoparticle (NP) paste with added soft polymer templates (SPT) followed by removal of the SPT at 500 °C. The SPTs consist of swollen crosslinked polymer colloids (microgels, MGs) or a commercial linear polymer (denoted as LIN). The MGs and LIN were comprised of the same polymer, which was poly(N-isopropylacrylamide) (PNIPAm). Large (L-MG) and small (S-MG) MG SPTs were employed to study the effect of template size. The SPT approach enabled pore size engineering in one deposition step. The SPT/TiO2 nanoparticle films had pore sizes > 100 nm; whereas, the average pore size was 37 nm for the control meso-TiO2 scaffold. The largest pore sizes were obtained using L-MG. SPT engineering increased the perovskite grain size in the same order as the SPT sizes: LIN < S-MG < L-MG and these grain sizes were larger than obtained using the control. The power conversion efficiencies (PCEs) of the SPT/TiO2-devices were ~ 20% higher than that for the control meso-TiO2 device and the PCE of the champion S-MG device was 18.8%. The PCE improvement is due to the increased grain size and more effective light harvesting of the SPT devices. The increased grain size was also responsible for the improved stability of the SPT/TiO2 devices. The SPT method used here is simple, scalable and versatile and should also apply to other PSCs.
关键词： Perovskite solar cells,template engineering,mesoporous TiO2,porosity,microgel,grain size.
更新于2025-09-23 15:21:01
-
Grain size dependence of tensile properties in nanocrystalline diamond
摘要： Nanocrystalline diamond (NCD) is a promising material due to its extraordinary mechanical properties, however, the research on the dependence of mechanical properties on the grain size (d) of NCD is still limited. In this paper, the mechanical behavior of 3D NCD with various d is investigated using molecular dynamics (MD) simulations. It was found that the mechanical properties of NCD are sensitive to d. The Young's modulus (E) increases with the increase of d due to the increasing fraction of grain interiors (GIs), while the failure strain (εf) decreases with the increase of d due to the decreasing fraction of grain boundaries (GBs). It was also found that the failure strength (σf) decreases with the increase of d, which could be attributed to that for larger d the stress concentration in the GBs is severer, which may make cracks initiate more easily. Similar to εf and σf, the deformation work density was found to increase with the decrease of d, indicating the enhancement of toughness of NCD when d is small. For the samples of different d, the nucleation and propagation of both transgranular and intergranular cracks are the main failure mechanisms, which is consistent with experimental observations.
关键词： Molecular dynamics simulation,Mechanical property,Nanocrystalline diamond,Tension,Grain size
更新于2025-09-23 15:21:01
-
Highly stable and efficient perovskite solar cells produced via high-boiling point solvents and additive engineering synergistically
摘要： The active absorber layer plays a crucial role in a perovskite solar cell. Herein, we used high boiling point γ-butyrolactone (GBL) as the main solvent, Pb(SCN)2 and dimethyl sulfoxide (DMSO) as an effective additive in the FA0.83MA0.17Cs0.05PbI(3?x)Brx solution to improve the quality of perovskite films. The GBL will delay the crystallization speed of the perovskite, and lead to the grain growth assisted by thiocyanate. The synergistic effect of the solvent engineering and additive engineering is beneficial to the slow growth of the grain size. It is found that the addition of Pb(SCN)2 increases Gibbs free energy barrier for the nucleation, leading to the formation of fewer nuclei, which results in a high quality of perovskite absorbers with larger grains and smoother surfaces. The synergistic effect of solvents and Pb(SCN)2 on the morphology and photovoltaic performances is investigated. Compared to devices without the additive, the efficiency of devices with 5% Pb(SCN)2-doped FA0.83MA0.17Cs0.05PbI(3?x)Brx is raised to 19.01% from 15.21%. We believe this breakthrough regarding high efficiency perovskite solar cells will help for their transitions.
关键词： efficiency,crystallinity,additive,perovskite,grain size
更新于2025-09-23 15:19:57
-
Microstructure refinement and properties of 1.0C-1.5Cr steel in a duplex treatment combining double quenching and laser surface quenching
摘要： The 1.0C-1.5Cr steel was subjected to conventional quenching and laser surface quenching treatment. A process combing double quenching and laser surface quenching was proposed for enhancing surface hardness and obtaining finer microstructure. The cementite dissolution and grain growth behavior in the austenitizing process of single quenching, double quenching, and laser surface quenching were studied. The results indicated that compared with single quenching, mean diameter of undissolved cementite particles (UCP) was much finer in double quenching, and the final prior austenite grain size (PAGS) could be decreased by nearly 40% to about 4.5 μm. Both grain and cementite particles near the surface will coarsen after laser surface treatment. Compared with single quenching, the PAGS within hardened layer can be decreased by at least 11% through double quenching, and the mean diameter of UCP at the bottom of hardened layer can be decreased by about 20%. Compared with conventional quenching, surface hardness was enhanced by about 20% through laser surface quenching, contributing to the wear resistance. However, the hard and brittle surface layer tends to be crack source during the impact process, leading to the deterioration of final impact toughness. Under the identical laser parameters, the impact absorbed energy is similar in both single and double quenching, which is about 25% of that before laser surface quenching. The impact absorbed energy can be increased from 22J to 28J by preheating at 160 C during the laser surface quenching.
关键词： Impact toughness,Grain size,Cementite,Laser surface quenching,Double quenching,Wear
更新于2025-09-19 17:13:59
-
Growth and characterization of ZnxSn1?xSe films for use in thin film solar cells
摘要： We have fabricated ZnxSn1?xSe (ZTSe) ?lms for the ?rst time. Samples were fabricated by chemical molecular beam deposition method at atmospheric pressure in hydrogen ?ow. ZnSe and SnSe powders with 99.999% purity were used as precursors. The temperature of precursors varied in the range of (850–950) °C. Films were deposited at substrate temperature of (500–600) °C. Borosilicate glass was used as a substrate. We have studied ZTSe ?lms by EDS, XRD and SEM. The samples had orthorhombic and cubic structures depending on composition. Results of EDS have shown that stoichiometric composition of samples moved to ZnSe side by increasing with substrate temperature. SEM pictures have shown that samples had polycrystalline structure. The grain size varied in the range of (2–15) μm. The grain size of samples increased from (2–5) μm to (15–20) μm for substrate temperatures of 500 °C and 550 °C respectively. While, at a substrate temperature of 600 °C the grain size decreased up to (3–5) μm, possibly, because of increasing of ZnSe content. XRD analysis has shown that samples have ZnSe, SnSe, Se and Sn phases. The band gap of samples varied in the range of 1.0–2.0 eV depending on the ?lm compositions. An inversion of the conductivity type was found: samples fabricated at 500 °C and 550 °C performed of p-type conductivity; while samples fabricated at 600 °C showed n-type conductivity.
关键词： Grain size,Conductivity,X-ray,ZnXSn1?XSe ?lms,Morphology
更新于2025-09-19 17:13:59