Fe-Mn damping alloys, which integrate high strength with superior damping capacity, are particularly suitable for manufacturing components with complex lattice or topological structures via additive manufacturing, enabling integrated lightweight and high-damping designs for load-bearing parts. In this work, Fe-20 Mn damping alloy was fabricated by selective laser melting (SLM), and its mechanical and damping properties were investigated. The as-SLMed alloy exhibits a fine microstructure, offering a tensile strength of 750 MPa, a yield strength of 505 MPa, and a damping performance Q -1 of 0.023 (at 6 x 10-4 strain). Annealing further improves both properties, achieving a yield strength of 621 MPa and Q -1 of 0.03. The enhancement is attributed to recrystallization, which transforms the high-defect, non-equilibrium SLMed state into a more stable structure strengthened by grain refinement and homogenized phase boundaries. Moreover, the increased stacking fault probability in epsilon and gamma phases, along with a higher density of epsilon-martensite variant boundaries and epsilon/gamma interfaces after annealing, raises the density of mobile interfaces, thereby directly boosting damping energy dissipation. This study systematically reveals the synergistic regulation of mechanical and damping properties in SLM-formed Fe-Mn alloys through heat treatment.

To address the fracture of ϕ5.5 mm high-strength welding wire steel ER55-D2-Ti rods during drawing caused by excessively high tensile strength， a systematic synergistic optimization of residual element control， steel cleanliness improvement， and controlled rolling and controlled cooling processes was conducted under full scrap electric arc furnace conditions. By establishing a precise scrap charging model and optimizing refining and RH vacuum degassing processes， the contents of Sn， As， and Sb were controlle withind 0.035%， 0.004 0%， and 0.002 0%， respectively. Meanwhile， the oxygen content in molten steel was decreased to below 15 ppm， and the type A inclusion level was controlled below 0.5. In addition，by adjusting the on-line cooling intensity，the laying temperature was narrowed to 800 ℃–815 ℃， and the cooling rate was reduced， thereby prolonging the ferrite phase transformation process. After the synergistic process optimization， the microstructure of the welding wire steel transformed into a dual-phase structure consisting of ferrite and granular bainite， with the ferrite volume fraction increasing from approximately 10% to about 40% and a pronounced grain refinement. The average tensile strength of the wire rod decreased by 115 MPa， while the strength variation within the same coil was reduced from 93 MPa to below 50 MPa. Consequently， the drawing performance of welding wire steel rods was improved ，wire breakage during drawing was significantly alleviated， and the welding spatter rate decreased from 4.78% to 1.33%. The results demonstrate that the coordinated regulation of chemical composition， steel cleanliness， and thermo-mechanical processing effectively enables the synergistic optimization of microstructure and mechanical properties of high-strength welding wire steel， providing an efficient technical pathway for stable production and quality improvement under full scrap electric arc furnace conditions.

Statement of problem. The selective laser melting (SLM) technique has been a promising method of fabricating Co-Cr metal-ceramic restorations; however, the lower metal-ceramic bond properties of SLM Co-Cr restorations have become a major issue in clinical use. Purpose. The purpose of this in vitro study was to propose and verify a method of improving the metal-ceramic bond properties of SLM Co-Cr alloy with heat treatment after porcelain firing (PH). Material and methods. Forty-eight (25x3x0.5 mm) Co-Cr specimens, divided into 6 groups (Control group [CG]; 550 degrees C; 650 degrees C; 750 degrees C; 850 degrees C; 950 degrees C) according to PH temperatures, were prepared by using SLM techniques. The 3-point bend tests were performed to evaluate the metal-ceramic bond strengths; subsequently, the fracture feature was assessed by using a digital camera and scanning electron microscope (SEM) coupled with an energy-dispersive X-ray spectroscopy (EDS) detector, to determine the area fraction of adherence porcelain (AFAP). The interface morphologies and element distribution were determined with SEM/EDS detectors. Phase identification and quantification were examined with an X-ray diffractometer (XRD). A 1way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values (alpha=.05). Results. The bond strengths were 35.33 +/- 1.25 MPa for the CG group, 34.53 +/- 3.20 MPa for the 550 degrees C group, 38.20 +/- 2.60 MPa for the 650 degrees C group, 42.85 +/- 2.31 MPa for the 750 degrees C group, 33.28 +/- 3.85 MPa for the 850 degrees C group, and 29.09 +/- 2.86 MPa for the 950 degrees C group. Significant differences were not observed among the CG, 550 degrees C, and 850 degrees C groups (P>.05) but were found among the other groups (P<.05). Fracture and AFAP results displayed a mixed fracture mode of adhesive and cohesive fracture. The thicknesses of native oxide films across the 6 groups were relatively close as the temperature increased, but the thickness of the diffusion layer increased as well. Excessive oxidation and massive phase transformation caused holes and microcracks to appear in the 850 degrees C and 950 degrees C groups, reducing bond strengths. XRD analysis evidenced that the phase transformation of gamma ->epsilon occurred at the interface during PH treating. Conclusions. PH treatment significantly affected the metal-ceramic bond properties of SLM Co-Cr porcelain specimens. The 750 degrees C-PH-treated specimens displayed higher mean bond strengths and improved fracture characteristics among the 6 groups.

This study undertakes vacuum pressureless brazing of SiC ceramics with TiSi2 powder, achieving MAX bonding. Microscopic characterization elucidates the microstructural evolution of the joined seam across various brazing temperatures and durations. The formation process of Ti3SiC2 is detailed through thermodynamic and kinetic analyses. At 1550 degrees C for 30 min or 1600 degrees C for 15 min, the filler undergoes in -situ reaction with SiC, yielding a dense, continuous Ti3SiC2 (MAX) phase, with no other phases observed. This suggests that increased temperature reduces MAX synthesis time. However, prolonged brazing causes voids in the center of the joined seam. Si volatilization was key for Ti3SiC2 in -situ formation, and this reaction equation was proposed. Maximum average shear strength at room temperature is 127.15 MPa at 1550 degrees C for 30 min and 118.15 MPa at 1600 degrees C for 15 min.

The current artificial bone is unable to accurately replicate the inhomogeneity and anisotropy of human cancellous bone. To address this issue, we proposed a personalized approach based on clinical CT images to design mechanical equivalent porous structures for artificial femoral heads. Firstly, supported by Micro and clinical CT scans of 21 bone specimens, the anisotropic mechanical parameters of human cancellous bone in the femoral head were characterized using clinical CT values (Hounsfield unit). After that, the equivalent porous structure of cancellous bone was designed based on the gyroid surface, the influence of its degree of anisotropy and volume fraction on the macroscopic mechanical parameters was investigated by finite element analysis. Furthermore, a mapping relationship between CT values and the porous structure was established by jointly solving the mechanical parameters of the porous structure and human cancellous bone, allowing the design of personalized gradient porous structures based on clinical CT images. Finally, to verify the mechanical equivalence, implant press-in tests were conducted on 3D-printed artificial femoral heads and human femoral heads, the influence of the porous structure’s cell size in bone-implant interaction problems was also explored. Results showed that the minimum deviations of press-in stiffness (<15

OBJECTIVES:To address the quality problems caused by high porosity in the preparation of dental cobalt-chrome alloy prosthetics based on selective laser melting (SLM) technology, we investigated the influence mechanism of different forming process parameters on the microstructure and properties of the materials. Moreover, the range of forming process parameters that can effectively reduce defects was precisely defined. METHODS:The effects of laser power, scanning speed, and scanning distance on the pore properties, surface roughness, and hardness of dental cobalt-chrome alloy were investigated by adjusting the printing parameters in the process of SLM. Through metallographic analysis, image analysis, and molten pool simulation, the pore formation mechanism was revealed, and the relationship between the porosity and energy density of SLM dental cobalt-chrome alloy was elucidated. RESULTS:When the linear energy density was higher than 0.18 J/mm, the porosity defect easily appeared at the bottom of the molten pool. When the laser energy density was lower than 0.13 J/mm, defects occurred in the gap of the molten pool due to insufficient melting of powder. In particular, when the linear energy density exceeded the threshold of 0.30 J/mm or was below 0.12 J/mm, the porosity increased significantly to more than 1%. In addition, we observed a negative correlation between free surface roughness and energy density and an inverse relationship between macroscopic hardness and porosity. CONCLUSIONS:On the basis of the conditions of raw materials and molding equipment used in this study, the key process parameters of SLM of molding parts with porosity lower than 1% were successfully determined. Specifically, these key parameters included the line energy density, which ranged from 0.13 J/mm to 0.30 J/mm, and the scan spacing should be strictly controlled below 90 μm.

The interfacial solar desalination has been considered a promising method to address the worldwide water crisis without sophisticated infrastructures and additional energy consumption. Although various advanced solar evaporators have been developed, their practical applications are still restricted by the unsustainable materials and the difficulty of precise customization for structure to escort high solar-thermal efficiency. To address these issues, we employed two kinds of naturally occurring molecules, tannic acid and iron (III), to construct a low-cost, highly efficient and durable interfacial solar evaporator by three-dimensional (3D) printing. Based on a rational structural design, a robust and 3D-printed evaporator with conical array surface structure was developed, which could promote the light harvesting capacity significantly via the multiple reflections and anti-reflection effects on the surface. By optimizing the height of the conical arrays, the 3D-printed evaporator with tall-cone structure could achieve a high evaporation rate of 1.96 kg m-2 h-1 under one sun illumination, with a photothermal conversion efficiency of 94.4%. Moreover, this evaporator was also proved to possess excellent desalination performance, recycle stability, anti-salt property, underwater oil resistance, as well as adsorption capacity of organic dye contaminants for multipurpose water purification applications. It was believed that this study could provide a new strategy to fabricate low-cost, structural regulated solar evaporators for alleviating the dilemma of global water scarcity using abundant naturally occurring building blocks.

Statement of problem. Dental cobalt-chromium (Co-Cr) alloy manufactured by selective laser melting (SLM) is not recommended for clinical applications before annealing because of excessive residual stress. However, limited information is available regarding the relationship between annealing temperature and the metal-ceramic bond properties of SLM Co-Cr alloys. Purpose. The purpose of this in vitro study was to investigate the effects of annealing temperature on the metal-ceramic bond properties of SLM Co-Cr alloys. Material and methods. Four groups with different annealing temperatures (850 C-circle; 950 C-circle; 1050 C-circle; 1150 C-circle) were prepared by using SLM techniques. Bond strengths were measured by using a 3-point bend test; subsequently, debonded surface morphologies and elements were assessed by using a scanning electron microscopy ( SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The area fraction of adherence porcelain (AFAP) value was introduced to analyze fracture characteristics. Microstructural and interfacial characteristics were characterized by SEM/EDS and X-ray diffraction analysis. The coefficient of thermal expansion (CTE) test was used to analyze thermal matching. A 1-way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values statistically (alpha=.05). Results. The mean +/- standard deviation values of the metal-ceramic bond strengths were 40.68 +/- 4.34 MPa for the 850 C-circle group, 37.54 +/- 5.34 MPa for the 950 C-circle group, 45.97 +/- 2.18 MPa for the 1050 C-circle group, and 50.79 +/- 1.79 MPa for the 1150 C-circle group. Significant differences (P <.05) were observed among all groups. Debonded surfaces and AFAP analysis displayed a mixed fracture mode of adhesive and cohesive fracture, and 1150(circle)C-annealing specimens exhibited better fracture characteristics close to cohesive fractures. As the temperature increased, native oxide film thicknesses remained unchanged; the 850(circle)C group had the thinnest diffusion layer, while the other 3 groups had similar thicknesses. Although the 1050 C-circle and 1150 C-circle groups displayed higher CTE values, their microstructures were more conducive to atomic diffusion and improved chemical bonding. Microstructure analysis found that e phase and second-phase precipitates jointly affected metal-ceramic bond strength. Conclusions. Annealing temperatures affected the metal-ceramic bond strengths of SLM Co-Cr porcelain specimens. 1150 C-circle annealing SLM Co-Cr specimens displayed higher bond strengths and improved fracture and interface characteristics among the 4 groups. (J Prosthet Dent 2023;129:657.e1-e9)

SiC作为潜在的下一代核反应堆包壳材料,实现其稳定可靠的连接是SiC基包壳管投入实际工程应用的重要一环.使用镍含量为 55at%的NiTi粉和Ni粉混合膏状钎料(NiTi+5Ni钎料)在 1350℃保温 10 min的工艺下实现了SiC陶瓷的连接.结果表明:焊缝界面区域组织为TiC连续反应层;中心区域基体组织为δ-Ni2Si+Ni3Si2 共析组织,其中弥散分布着大量的TiC颗粒.接头平均室温剪切强度可达 125 MPa,断裂位于靠近界面的SiC陶瓷内部.界面处TiC与SiC之间良好的晶格匹配度以及焊缝中心区域的TiC颗粒对接头热残余应力的缓解,提升了接头的力学性能.

在真空环境下对轧制态Fe-11Cr-2.5Mo-1Ni-0.1Zr进行 3 种不同退火温度的热处理,通过TA Q800 动态机械分析仪研究了不同退火温度下合金在不同恒定预应力下的阻尼性能.结果表明:随预应力的增加,阻尼合金的阻尼性能衰减.经 950℃退火后,阻尼衰减的幅度最小;经 900℃退火处理后,在 24 MPa预应力下,合金获得最优异的阻尼性能.通过扫描电镜观察到合金经退火处理后获得以铁素体为基体、马氏体为析出相的双相组织;经光学显微镜观察到,随退火温度的增加,合金中获得的马氏体相的含量随之增加.

In this study, we investigate the influence of grain boundary character on isothermal phase transformation and mechanical properties of selective laser melting (SLM) fabricated Co-Cr-Mo alloy. The grain boundary engineering (GBE) was used to manipulate the isothermal phase transformation and precipitation. The AsSLM Co-Cr-Mo and GBE Co-Cr-Mo alloys were isothermal treatment at 800 degrees C for 6 h in a muffle furnace, followed by air cooling, respectively. It was found that the high density of stacking faults and low-angle boundaries in As-SLM Co-Cr-Mo alloy accelerated the phase transformation of gamma-Co to epsilon-Co and Laves phase precipitation, which improved the tensile strength and drastically deteriorated the ductility. While, the high fraction of twin boundaries in GBE Co-Cr-Mo alloy retard the isothermal phase transformation and improve the resistance to Laves phase precipitation, which nearly maintain the high mechanical performance after the same isothermal treatment. The results of this study can be a guide to fabricate high-performance Co-Cr-Mo alloy according to work conditions. (C) 2022 Elsevier B.V. All rights reserved.

为预防和应对核电站事故,ATF(Accident Tolerant Fuel)材料的概念应运而生,包覆核燃料芯体的包壳管的材料选用及制造于此具有重要意义.SiC陶瓷凭借其优异的力学性能、耐腐蚀性能及抗辐照性能,成为下一代核燃料包壳管的候选材料.受限于SiC陶瓷的固有特性,SiC基包壳管难以一体成形,为确保端盖处气密性,SiC的连接技术成为国内外学者的研究重点.就SiC陶瓷基本性质、核领域应用前景和制备方法等方面进行了介绍.着重整理了SiC陶瓷的扩散焊连接和钎焊连接等常用连接技术研究现状,分析了Ti、Mo和Ni/Ti等扩散焊连接材料及Ag-Cu基、Pd基、Co基、Ni基、Ti基和Al基等钎料的优劣,论述了不同连接材料在高温、辐照、腐蚀等环境下的性能差异.就SiC陶瓷的连接技术在核包壳管的应用方面进行了评价及展望.

Present proposed mechanisms for ageing-induced martensitic stabilization cannot explain why the amount of martensites losing reverse transformation ability (RTA) positively depended on Ms temperatures in directly-quenched CuZnAl alloys owing to dynamic ageing during the cooling process of quenching and subsequent slow heating. We proposed and confirmed that the number of vacancies at martensites boundaries (Nvmb) was the key factor controlling the occurrence of martensitic stabilization and its resulting RTA or loss in shape memory effect, not the number of vacancies inside the martensites and their long-range diffusion. All reported results can be rationalized by the positive dependence of original Nvmb on the Ms temperature.

This paper compared the mechanical properties and damping capacity of homogeneous welded joints of Mn-36Cu-3Al-2Zn-2Ni-2Fe (wt.%) cast damping alloy by pulsed and non-pulsed current TIG welding. The results show that the pulsed current makes the microstructure finer in the welded seam due to its rapid solidification of the welding pool and fragmentation of the rough dendrite arm. Tensile and impact tests show that pulsed current welded joints have better mechanical properties than non-pulsed current welded joints, as the strength and toughness of the joints increased by 6.6 and 25.2%, respectively. In addition, according to damping capacity test results, the larger Mn-rich regions in the pulsed current welded seam result in a larger f.c.c-f.c.t phase transformation and more fine martensitic twins. Thus, the damping capacity of the welded joint under pulsed current is 27.6% higher than that under non-pulsed current and far higher than that of the base metal. The addition of pulsed current significantly improves the mechanical properties and damping capacity of the alloy welded joint.

The effect of annealing at 700, 800, 900 and 1000°C on the microstructure and mechanical properties of alloy Ti – 6% Al – 4% V obtained by selective laser melting is studied. The ultimate tensile strength, the yield strength, the elongation, and the hardness of samples of the titanium alloy are determined in the initial condition and after annealing. X-ray diffraction and phase analyses are performed. The changes in the structure of the alloy during annealing at different temperatures are analyzed. It is shown that the intensity of the structural changes increases with the annealing temperature, while the microhardness and the strength characteristics decrease, and the ductility grows.

Previous work did not identify occurrence stage and degree of martensitic stabilization in Cu-based shape memory alloys due to lower heating rate. By flash heating into liquid metals, we systematically clarified contribution of static ageing and the ones of dynamic ageing during process of quenching and heating to the martensitic stabilization in directly-quenched CuZnAl alloys. We discovered that the dynamic ageing during the cooling process of quenching could instantaneously stabilize a few already formed martensites totally although it did not stabilize the overwhelming majority of martensites. The dynamic ageing during the process of subsequent slow heating was responsible for the partial and total stabilization of overwhelming majority of martensites. Both the amounts of martensites stabilized totally by the two dynamic ageing positively depended on Ms temperature. The conventional up-quenching into oil or air actually made more martensites stabilized due to the dynamic ageing during the process of slow heating. The increase in As temperature owing to the static ageing also positively depended on the Ms temperature. These dependences cannot be explained by two well-known mechanisms for the martensitic stabilization.

对锻造Fe-11Cr-2.5Mo-1Ni-0.1Zr阻尼钢板进行钨极氩弧同质焊接.从焊后钢板上取样,在真空环境下进行900℃保温1h随炉冷却热处理.通过TAQ800动态机械分析仪研究了合金在不同预应力下的阻尼性能.结果表明:随着施加的预应力的增大,合金的阻尼性能降低,但下降的幅度不大.用万能试验机和冲击试验机研究焊接合金的力学性能,发现焊后合金具有良好的力学性能,且焊缝的强度高于母材.通过扫描电镜观察到了冲击试样的断口上存在大量冲击过程中因塑性变形而形成的纤维组织和韧窝组织,它们有效地吸收了冲击功,阻止了裂纹的扩展,合金的断裂方式为韧性断裂.

Co-Cr alloy fabricated by selective laser melting was used to investigate the recrystallization behavior and grain boundary character evolution from As-SLM to isothermal annealed at 1200 degrees C for 5 min to 60 min. The As-SLM Co-Cr alloy has a prominent residual strain, high densities of dislocations and stacking faults, and solute segregation along the subgrain boundaries. The driving force for recrystallization of As-SLM Co-Cr alloy is mainly provided by phase transformation rather than crystal defects, which also offer plenty of routeways for both lowand high-angle grain boundary diffusion. In addition, the stacking faults in As-SLM Co-Cr alloy can generate morphologically complex twins by extending and gliding. The obtained optimal Co-Cr alloy has a large fraction (more than 80%) of special boundaries (sigma 3, sigma 9, and sigma 27) after complete recrystallization, which enables high designing freedom and near-net-shape production towards additive manufacturing (AM) compatible grain boundary engineering (GBE) processing strategy.

STATEMENT OF PROBLEM:The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental restorations are fatigue failure. The 4-point bend fatigue behavior of Co-Cr-Mo-W alloys manufactured by investment casting (CAST) and selective laser melting (SLM) has received little attention. PURPOSE:The purpose of this in vitro study was to evaluate the 4-point bend fatigue property of dental Co-Cr alloys and determine the relationship between microstructure and the 4-point bend fatigue property of Co-Cr alloys created by traditional casting and SLM. These can guide the use of Co-Cr alloy in dentistry. MATERIAL AND METHODS:Co-Cr-Mo-W alloys were fabricated with a dimension of 45×2×2 mm by investment casting and SLM. The 3-point bend test measured the ultimate bend strength with 3 specimens in each group. The 4-point bend fatigue test evaluated the fatigue life under various stresses, with 6 specimens in each group. The specimens were mechanically ground, polished, and electrochemically etched. Scanning electron microscopy was used to identify the microstructures of both etched specimens and fracture surfaces. X-ray diffraction investigations were used to determine the phases. Significant differences in the bend strength were analyzed by using the independent samples t test (α=.05), and the fatigue test was analyzed with ANCOVA (α=.05). RESULTS:The mean ±standard deviation bend strength of SLM specimens was 1837 ±3 MPa, higher than the 1200 ±6 MPa for CAST specimens (P<.05). The maximum bend stress of the SLM specimens without fatigue failure was 735 MPa, which was statistically higher than the 394 MPa for CAST specimens (P<.05). The microstructure characteristics of the SLM alloy contributed to its excellent fatigue performance. In SLM alloy, the γ phase constituted the majority with some ε and Laves phases, while the cast alloy possessed higher ε and Laves phases. The grains of SLM alloy were equiaxed and fine, and the second phases were fine and dispersive. In contrast, the cast alloy possessed clear dendrites, and the second phases were sizable. CONCLUSIONS:The SLM dental Co-Cr-Mo-W alloy had statistically better 4-point bend fatigue properties than cast alloy, which was associated with an improved microstructure.

The microstructure and mechanical property of Ti-14Al-10Nb alloy as casted condition which carried out at heat treatment temperatures were studied. Through the X-ray diffraction and microstructure observed, it can be indicated that the microstructure of Ti-14Al-10Nb alloys was composed of α2 phase and β phase in cast condition. During the heat treatment process, the content of α2 phase decreased and accompanied by the thickness of α2 phase reduced as the temperature rose. As casted condition, the compression strength of Ti-14Al-10Nb alloy was 1320 MPa, and compressive strain was 0.161. The element Al and Nb solubilized in β phase leading to the solution strengthening strengthened during heat treatment process, so the plastic property of Ti-14Al-10Nb alloy was deteriorated. While alloy carried out at 900℃ for 60 minutes, the compressive strain was only 0.0236. Meamwhile, the trend of compression strength was first falling then rising as a result of comprehensive effect of phase strengthening and solution strengthening.