Materials Characterization最新文献

英文中文

Quantitative revealing the solute segregation behavior at melt pool boundary in additively manufactured stainless steel using a novel processing method for precise positioning by HAADF-STEM 利用 HAADF-STEM 精确定位的新型加工方法定量揭示添加式制造不锈钢中熔池边界的溶质偏析行为

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-05 DOI: 10.1016/j.matchar.2024.114435

Laser-powder bed fusion (LPBF) enables the fabrication of complex metallic components by manipulating various laser scan strategies to control microstructure and texture. Multiple thermal cycling and rapid solidification lead to non-equilibrium, non-uniform microstructure, and micro-segregation at the melt pool boundary (MPB), whose accurate location is still invisible by transmission electron microscopy (TEM), and quantitative concentration remains imprecise. In this study, we proposed a novel method to make it clear by controlling the crystallographic texture of 316 L stainless steel through unique LPBF processing parameters to obtain a single-crystal-like microstructure of the cellular structures along the laser scanning direction. The accurate location of the track-track MPB is distinguishable by means of the transverse and longitudinal cellular dislocation structures on both sides. The edge-on state of the track-track MPB makes the quantitative concentration analysis precisely using high-angle annular dark-field scanning TEM with energy-dispersive X-ray spectroscopy, which is in good agreement with the Scheil-Gulliver solidification simulations.

激光粉末床熔融技术（LPBF）可通过操纵各种激光扫描策略来控制微观结构和质地，从而制造出复杂的金属部件。多次热循环和快速凝固会导致熔池边界（MPB）出现非平衡、不均匀的微观结构和微观偏析，而透射电子显微镜（TEM）仍无法看到MPB的准确位置，定量浓度也不精确。在这项研究中，我们提出了一种新颖的方法，通过独特的 LPBF 加工参数控制 316 L 不锈钢的结晶纹理，沿激光扫描方向获得单晶样的蜂窝状微观结构，从而使其清晰可见。通过两侧的横向和纵向蜂窝状位错结构，可以分辨出轨道轨迹 MPB 的准确位置。利用高角度环形暗场扫描 TEM 与能量色散 X 射线光谱法，可对轨迹 MPB 的边缘状态进行精确的定量浓度分析，这与 Scheil-Gulliver 凝固模拟结果十分吻合。

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引用次数: 0

Enhanced high-temperature mechanical properties and strengthening mechanisms of chemically prepared nano-TiC reinforced IN738LC via laser powder bed fusion 通过激光粉末床熔融技术提高化学制备的纳米钛强化 IN738LC 的高温力学性能和强化机理

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-04 DOI: 10.1016/j.matchar.2024.114434

Fabrication of high-strength nickel-based composites to meet the demanding service requirements in aerospace environments is a significant challenge. This paper introduces the wet chemical method to prepare the nano-TiC reinforced IN738LC. In contrast to the conventional ball milling approach, this method attains superior attachment of nanoparticles. By employing a full-factorial experimental design, the correlation between Laser-powder bed fusion (L-PBF) processing parameters and the porosity, micro-hardness, and high-temperature tensile strength of as-built samples was examined. The results indicate that the optimal processing parameters are a laser power of 225 W, scanning speed of 750 mm/s, and hatch space of 0.09 mm, with a Volumetric energy density (VED) of 111.1 J/mm³. Compared to IN738LC, the chemically prepared TiC-IN738LC exhibits a 45 % increase in room temperature tensile strength (400 MPa) and a 65 % increase in high-temperature tensile strength (120 MPa). Compared with ball-milled TiC-IN738LC, the chemically prepared samples present superior microstructure with more equiaxed grains. The morphological analysis of the tensile samples reveals that the presence of dimples are crucial in enhancing the ductility properties. Furthermore, this study identifies the Orowan strengthening mechanism and the grain refinement strengthening mechanism as the principal mechanisms of reinforcement by nano-ceramics.

制备高强度镍基复合材料以满足航空航天环境中苛刻的使用要求是一项重大挑战。本文介绍了制备纳米 TiC 增强 IN738LC 的湿化学方法。与传统的球磨法相比，该方法能获得更佳的纳米颗粒附着效果。通过采用全因子实验设计，考察了激光粉末床熔融（L-PBF）加工参数与坯料样品的孔隙率、微硬度和高温抗拉强度之间的相关性。结果表明，最佳加工参数为激光功率 225 W、扫描速度 750 mm/s、舱口空间 0.09 mm、体积能量密度 (VED) 111.1 J/mm3。与 IN738LC 相比，化学制备的 TiC-IN738LC 的室温抗拉强度（400 兆帕）提高了 45%，高温抗拉强度（120 兆帕）提高了 65%。与球磨 TiC-IN738LC 相比，化学制备的样品具有更优异的微观结构，具有更多的等轴晶粒。拉伸样品的形态分析表明，凹坑的存在对提高延展性能至关重要。此外，本研究还发现奥罗万强化机制和晶粒细化强化机制是纳米陶瓷的主要强化机制。

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引用次数: 0

The effect of oxide scale on the corrosion resistance of SUS301L stainless steel welding joints 氧化鳞对 SUS301L 不锈钢焊接接头耐腐蚀性的影响

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-02 DOI: 10.1016/j.matchar.2024.114431

The effect of thermal oxidates on the corrosion of SUS301L stainless steel welded joint was investigated using electrochemical corrosion test and TEM microstructure observation. Activation dissolution behavior without passive region was found in the potentiodynamic polarization curves on the welding zone and heat affected zone. The activation corrosion is related to the preferential dissolution of the NiFe layer at the interface between chromium oxide and substrate. However, the passive region in the polarization curve reappears after the unstable NiFe dissolves in the salt-frog test. The passivation behavior due to microstructure evolution beneath the thermal oxide film was discussed during the corrosion process.

利用电化学腐蚀试验和 TEM 显微结构观察研究了热氧化物对 SUS301L 不锈钢焊接接头腐蚀的影响。在焊接区和热影响区的电位极化曲线中发现了无被动区的活化溶解行为。活化腐蚀与氧化铬和基体界面上的镍铁合金层优先溶解有关。然而，在盐蛙试验中，不稳定的镍铁层溶解后，极化曲线中的被动区再次出现。在腐蚀过程中，讨论了热氧化膜下微观结构演变导致的钝化行为。

引用次数: 0

Achieving high strength and ductility of Al-Zn-Mg-Cu alloys via laser shock peening and spray forming 通过激光冲击强化和喷射成形实现铝-锌-镁-铜合金的高强度和延展性

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-01 DOI: 10.1016/j.matchar.2024.114427

In order to further enhance the strength and ductility of ultra-high strength aluminum alloys, the laser shock peening technology was applied to ultra-high strength Al-Zn-Mg-Cu alloy. The ultimate tensile strength, elongation and hardness can reach to 751 MPa, 11 % and 208.3 HV by combining spray forming, secondary extrusion, solid solution, retrogression and reaging as well as laser shock peening. The high strength and hardness of the alloys is mainly attributed to the fine-grained layer on surface as well as new grain boundaries, dislocation cells and high-density dislocations introduced by laser shock peening, uniform nano-sized strengthening phases with high density precipitated during heat treatments. The excellent ductility of the alloys is mainly ascribed to multiple structures including fine-grained layer on surface and slip lines inside different grains introduced by laser shock peening, smaller size of fibrous grains and Al₇Cu₂Fe phase produced by secondary extrusion and spray forming. The aging treatment after laser shock peening can lead to the annihilation of high-density dislocations as well as significantly promote the formation of stable and coarse η phase, which can greatly reduce the strength of the studied alloys.

为了进一步提高超高强度铝合金的强度和延展性，将激光冲击强化技术应用于超高强度铝-锌-镁-铜合金。通过结合喷射成形、二次挤压、固溶、回火和时效以及激光冲击强化技术，其极限拉伸强度、伸长率和硬度分别达到 751 兆帕、11% 和 208.3 HV。合金的高强度和高硬度主要归功于表面的细晶粒层以及激光冲击强化引入的新晶界、位错单元和高密度位错，以及热处理过程中析出的高密度均匀纳米级强化相。合金的优异延展性主要归因于多种结构，包括激光冲击强化引入的表面细晶粒层和不同晶粒内部的滑移线、较小尺寸的纤维晶粒以及二次挤压和喷射成形产生的 Al7Cu2Fe 相。激光冲击强化后的时效处理可导致高密度位错的湮灭，并显著促进稳定粗大的 η 相的形成，从而大大降低所研究合金的强度。

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引用次数: 0

Revealing the substantial impact of trace Mg addition on the microstructural configuration of a cast Al-Li-Cu-Zr alloy under various conditions 揭示微量镁添加在不同条件下对铝-锂-铜-锌铸造合金微观结构构造的重大影响

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-01 DOI: 10.1016/j.matchar.2024.114428

In this study, the impact of 0.2 wt% Mg addition on the microstructural configuration of a cast Al-2.5Li-2.5Cu-0.15Zr alloy under different heat treatment conditions was investigated using multiscale characterization. Results indicate that in the as-cast state, trace Mg forms the low-melting-point Al₂CuMg eutectic phases and promotes grain refinement. In the natural aging state, trace Mg promotes the precipitation of fine Guinier-Preston (GP) zones independent of pre-existing δ′-Al₃Li phases. In the artificial aging state, trace Mg mainly leads to the inducing of GP zones, suppression of θ′-Al₂Cu phases, and promotion of T₁-Al₂CuLi phases. δ′ phases with slight diameter reduction and minimal S′-Al₂CuMg phases with two variants are also observed. Atomic-level analysis of the two newly formed composite precipitates indicates that L1₂ structure phases on both sides of the GP zone have an anti-phase relationship. This study is expected to provide theoretical insights into the microstructural origins underlying the beneficial effects of Mg microalloying in cast Al-Li-Cu alloys.

本研究采用多尺度表征方法研究了在不同热处理条件下，添加 0.2 wt% 的镁对铸造 Al-2.5Li-2.5Cu-0.15Zr 合金微观结构配置的影响。结果表明，在铸造状态下，微量镁形成低熔点的 Al2CuMg 共晶相，并促进晶粒细化。在自然老化状态下，痕量镁促进了细小的吉尼尔-普雷斯顿（GP）区的沉淀，而与预先存在的δ′-Al3Li 相无关。在人工老化状态下，微量镁主要导致诱发 GP 区，抑制 θ′-Al2Cu 相，促进 T1-Al2CuLi 相。此外，还观察到直径略有减小的δ′相和具有两种变体的最小 S′-Al2CuMg 相。对两种新形成的复合沉淀的原子级分析表明，GP 区两侧的 L12 结构相具有反相关系。这项研究有望为研究铸铝-锂-铜合金中镁微合金化的有利影响的微观结构起源提供理论依据。

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引用次数: 0

Characterization of L12-Al3Ce phase and its purification mechanism in the Al-Ce-TiCN alloy Al-Ce-TiCN 合金中 L12-Al3Ce 相的特征及其纯化机制

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-01 DOI: 10.1016/j.matchar.2024.114425

Rare earth element Ce has a positive purifying effect on Fe and Si impurities in pure aluminum. In this study, we unveiled the mechanism of Ce purification of Fe and Si impurities in commercial pure aluminum at the atomic scale via utilizing the properties of TiCN nanoparticles, which exhibit distribution along grain boundaries and impede solute atom diffusion at specific cooling rates. The transition phase L1₂-Al₃Ce was characterized in aluminum, which is considered to be an important transition phase to purified products. Furthermore, High Angle Dark Field Scanning Transmission Electron Microscopy (HADDF-STEM) and 3D Atom Probe Tomography (3D-APT) results showed that Ce could respectively enrich the Fe and Si impurities, resulting in the formation of Al-Ce-Fe and Al-Ce-Si clusters. Density functional theory (DFT) results indicated that Fe and Si atoms can incorporate into L1₂-Al₃Ce crystal, forming more stable structures and therefore giving rise to the formation of Al-Ce-Si and Al-Ce-Fe nanoclusters. This study provides atomic-scale insights into the mechanism of Ce purifying Fe and Si impurities in aluminum.

稀土元素 Ce 对纯铝中的铁和硅杂质具有积极的净化作用。在这项研究中，我们利用 TiCN 纳米粒子的特性，在原子尺度上揭示了 Ce 在商业纯铝中提纯铁和硅杂质的机理，TiCN 纳米粒子沿晶界分布，并在特定冷却速率下阻碍溶质原子扩散。对铝中的过渡相 L12-Al3Ce 进行了表征，该相被认为是纯化产品的重要过渡相。此外，高角度暗场扫描透射电子显微镜（HADDF-STEM）和三维原子探针断层扫描（3D-APT）结果表明，Ce 可分别富集 Fe 和 Si 杂质，从而形成 Al-Ce-Fe 和 Al-Ce-Si 团簇。密度泛函理论（DFT）结果表明，Fe 原子和 Si 原子可以融入 L12-Al3Ce 晶体，形成更稳定的结构，从而形成 Al-Ce-Si 和 Al-Ce-Fe 纳米团簇。这项研究从原子尺度上揭示了 Ce 净化铝中 Fe 和 Si 杂质的机理。

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引用次数: 0

Effect of microalloying on the properties and Cr precipitate thermal stability of Cu-Cr-Nb alloys 微合金化对铜-铬-铌合金性能和铬析出物热稳定性的影响

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-01 DOI: 10.1016/j.matchar.2024.114426

The Cu-Cr-Nb alloy's high-temperature property is well known for the heat-sink application in rocket engine combustion chambers. Effects of Ti, Si, and Co microalloying elements on the microstructure and mechanical properties at high temperatures were investigated in detail. Cu-Cr-Nb alloy ingots were prepared using the atmospheric melting method and the growth rate of Cr precipitates in the studied alloys was explored. After aging at 450 °C for 60 min, the tensile strengths of Cu-2.6Cr-0.9Nb-0.15Ti (at. %) alloy were measured as follows: 468 MPa at 20 °C, 318 MPa at 400 °C, 281 MPa at 450 °C, 238 MPa at 500 °C, 187 MPa at 550 °C, and 140 MPa at 600 °C. The addition of trace Ti element effectively reduced the growth rate of Cr precipitates during high-temperature strain and contributed to the high-temperature mechanical properties. These findings are meaningful in developing high-strength Cu–Cr–Nb alloys at high temperatures.

众所周知，Cu-Cr-Nb 合金的高温性能主要用于火箭发动机燃烧室的散热器。研究人员详细探讨了 Ti、Si 和 Co 微合金元素对高温下微观结构和机械性能的影响。采用常压熔炼法制备了 Cu-Cr-Nb 合金铸锭，并探讨了所研究合金中铬析出物的生长率。Cu-2.6Cr-0.9Nb-0.15Ti (at. %) 合金在 450 °C 下老化 60 分钟后，拉伸强度的测量结果如下：20 °C 时为 468 MPa，400 °C 时为 318 MPa，450 °C 时为 281 MPa，500 °C 时为 238 MPa，550 °C 时为 187 MPa，600 °C 时为 140 MPa。痕量钛元素的添加有效地降低了高温应变过程中铬析出物的增长速度，有助于提高高温机械性能。这些发现对开发高温下的高强度 Cu-Cr-Nb 合金很有意义。

引用次数: 0

Enhancing mechanical property and corrosion resistance of Al0.3CoCrFeNi1.5 high entropy alloy via grain boundary engineering 通过晶界工程提高 Al0.3CoCrFeNi1.5 高熵合金的机械性能和耐腐蚀性能

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-10-01 DOI: 10.1016/j.matchar.2024.114420

In the present study, to improve the performances of Al_0.3CoCrFeNi_1.5 high entropy alloys (HEAs), grain boundary character distribution (GBCD) of Al_0.3CoCrFeNi_1.5 HEA has been optimized by an appropriate thermo-mechanical processing. The experiment results showed that the fraction of low-Σ coincidence site lattice (CSL) boundaries could reach approximately 80 % through cold rolling with deformation of 8 % and subsequent annealing at 1050 °C for 5 min. The reason for GBCD optimization could be attributed to sufficient strain-induced boundary migration (SIBM) or grain growth after recrystallization. While recrystallization is not favorable for optimizing GBCD. The mechanical properties and corrosion resistance have been enhanced, with a more pronounced improvement observed in the corrosion resistance. The corrosion current density i_corr of the GBEM specimen stands at 0.23 μA∙cm⁻², representing a reduction of 66 % in comparison to the BM specimen (0.68 μA∙cm⁻²). The improvement of corrosion resistance of Al_0.3CoCrFeNi_1.5 HEA resulted from the discontinuous random grain boundaries (RGBs) broken by the high fraction of low-ΣCSL boundaries, especially Σ3 boundaries suppressed the propagation of corrosion crack.

在本研究中，为了提高 Al0.3CoCrFeNi1.5 高熵合金（HEAs）的性能，通过适当的热机械加工优化了 Al0.3CoCrFeNi1.5 HEA 的晶界特征分布（GBCD）。实验结果表明，通过变形量为 8% 的冷轧和随后在 1050 °C 下退火 5 分钟，低Σ共轭晶格 (CSL) 晶界的比例可达到约 80%。GBCD 优化的原因可能是再结晶后充分的应变诱导边界迁移（SIBM）或晶粒生长。而再结晶不利于 GBCD 的优化。机械性能和耐腐蚀性能都得到了提高，耐腐蚀性能的提高更为明显。GBEM 试样的腐蚀电流密度 icorr 为 0.23 μA∙cm-2，与 BM 试样（0.68 μA∙cm-2）相比降低了 66%。Al0.3CoCrFeNi1.5 HEA 耐腐蚀性能的提高源于不连续的随机晶界（RGB）被高比例的低ΣCSL 晶界打破，尤其是Σ3 晶界抑制了腐蚀裂纹的扩展。

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引用次数: 0

The microstructure and mechanical properties of the laser-welded joints of as-hot rolled AlCoCrFeNi2.1 high entropy alloy 热轧 AlCoCrFeNi2.1 高熵合金激光焊接接头的显微组织和力学性能

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-09-30 DOI: 10.1016/j.matchar.2024.114423

AlCoCrFeNi_2.1 hot-rolled eutectic high entropy alloys were welded by laser welding, yielding a free-defect laser-welded connection. With the use of optical microscopy, EDS, EBSD, and XRD, the microstructure of the base metal (BM), fusion zone (FZ), and heat-affected zone (HAZ) of the joint was examined. The produced joint underwent tensile and micro-hardness testing as well as a fracture morphology examination. A similar tensile strength in the FZ and BM is measured, while a decrease in the elongation. The typical layered lamellar structures, in particular an FCC + BCC dual-phase structure, were all visible in the HAZ, BM, and FZ zones. The α-fiber and γ-fiber as well as other textures are determined by the ODF figure, indicating a potential orientation distribution of the as-hot rolled AlCoCrFeNi_2.1 joint. A clear grain refinement characteristics in the fusion zone as a result of the uneven thermal cycling during the welding process. The results of the mechanical test demonstrate the base metal has the highest hardness value, i.e. 500–550 HV_0.2, within the welded joint zone. The welded joint has a tensile strength ∼1200 MPa, which is marginally higher than ∼1150 MPa in the base metal, and an elongation that decreases by 20 % from base metal to welded joint, indicating a decrease in the plasticity of the welded joint. A combination of brittle and ductile fracture occurs in welded joints during tensile failure. This study may give possibilities for the engineering application of laser welding of AlCoCrFeNi_2.1 eutectic high entropy alloy in the future.

用激光焊接了 AlCoCrFeNi2.1 热轧共晶高熵合金，获得了无缺陷激光焊接连接。利用光学显微镜、EDS、EBSD 和 XRD 检查了接头母材 (BM)、熔合区 (FZ) 和热影响区 (HAZ) 的微观结构。生产出的接头还进行了拉伸和显微硬度测试以及断口形态检查。测量结果表明，FZ 和 BM 的拉伸强度相似，但伸长率有所下降。在 HAZ、BM 和 FZ 区都能看到典型的层状薄片结构，特别是 FCC + BCC 双相结构。ODF 图确定了 α 纤维和 γ 纤维以及其他纹理，表明了热轧铝钴铬铁镍 2.1 接头的潜在取向分布。由于焊接过程中不均匀的热循环，熔合区出现了明显的晶粒细化特征。机械测试结果表明，在焊点区域内，母材的硬度值最高，即 500-550 HV0.2。焊接接头的抗拉强度为 1200 兆帕，略高于母材的 1150 兆帕，从母材到焊接接头的伸长率降低了 20%，表明焊接接头的塑性降低。在拉伸破坏过程中，焊点会发生脆性和韧性断裂的结合。这项研究可能为未来 AlCoCrFeNi2.1 共晶高熵合金的激光焊接工程应用提供可能性。

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引用次数: 0

Unexpected thermal aging effect on brittle fracture and elemental segregation in modern dissimilar metal weld 热老化对现代异种金属焊缝脆性断裂和元素偏析的意外影响

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-09-30 DOI: 10.1016/j.matchar.2024.114419

A full-scale dissimilar metal weld safe-end mock-up, precisely replicating a critical component of a modern nuclear power plant, was investigated. The brittle fracture behavior, carbide evolution and nanoscale elemental segregation in the heat-affected zone (HAZ) of low alloy steel (LAS) were analyzed under both post-weld heat-treated and thermally-aged conditions (400 °C for 15,000 h, equivalent to 90 years of operation) using analytical electron microscopy and atom probe tomography. The observed increase in grain boundary (GB) decohesion and intergranular cracking on the fracture surface and the decrease of fracture toughness are primarily attributed to P and Mn segregation to GBs and the coarsening of carbides upon long-term thermal aging. The direct observations of significant elemental segregation to GBs and the consequent reduction in fracture toughness in the HAZ are unexpected for modern low-phosphorus LASs, highlighting potential concerns for evaluating the structural integrity of modern nuclear power plants.

对精确复制现代核电厂关键部件的全尺寸异种金属焊接安全端模型进行了研究。利用分析电子显微镜和原子探针断层扫描技术，分析了低合金钢（LAS）在焊后热处理和热老化（400 °C，15,000 小时，相当于运行 90 年）条件下的脆性断裂行为、碳化物演变和热影响区（HAZ）中的纳米级元素偏析。所观察到的晶界（GB）脱粘和断裂表面晶间裂纹的增加以及断裂韧性的降低主要归因于 P 和 Mn 在 GB 上的偏析以及长期热老化后碳化物的粗化。对于现代低磷 LAS 而言，直接观察到大量元素偏析到 GB 以及 HAZ 断裂韧性随之降低是意料之外的，这凸显了评估现代核电站结构完整性的潜在问题。

引用次数: 0

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