Materials Characterization最新文献_第4页

Effect of Mg/Si ratio and content on the microstructure and mechanical properties of cast Al-Li-Cu alloy Mg/Si比和含量对铸态Al-Li-Cu合金组织和力学性能的影响

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116089

Lixiong Shao , Gaoqiu Sun , Zhiping Wang , Hui Liu , Yilei Fu , Xianfeng Li , Dong Chen

This study systematically investigates the effects of dual Mg and Si additions on microstructural evolution and mechanical properties of a cast Al-Li-Cu alloy. The Mg and Si contents and their ratio (Mg/Si) strongly influence phase formation during solidification, dissolution behavior during solution treatment, and precipitation evolution during aging. Increasing the Mg/Si ratio promotes the formation of Mg₂Si and suppresses AlLiSi formation, particularly at a Mg/Si ratio of 3. However, excessive Mg additions (>2.4 wt%) lead to severe grain-boundary segregation and promote the formation of low-melting-point phases, such as Al₂CuMg and complex Al-Li-Cu-Mg phases, thereby reducing the incipient melting temperature and hindering complete dissolution during solution treatment. Alloys with moderate Mg and Si contents (e.g., 5M2S and 12M4S alloys) exhibit more effective dissolution of Cu-rich phases, while those with excessive additions retain coarse undissolved particles that deteriorate fracture toughness. During aging, Mg and Si additions inhibit θ' precipitation, promote a more uniform distribution of T₁ and nanoscale Mg₂Si precipitates, and suppress the coarsening of δ′-Al₃Li. Consequently, pronounced solid-solution and precipitation strengthening are achieved. Among the investigated alloys, the 5M2S alloy exhibits an optimal balance of strength and ductility after aging at 175 °C for 8 h, achieving a yield strength of 291 MPa, an ultimate tensile strength of 381 MPa, and an elongation of 3.1%. These findings elucidate the synergistic roles of Mg and Si in tailoring microstructural evolution and provide practical guidance for designing high-performance cast Al-Li-Cu alloys.

本研究系统地研究了Mg和Si双添加对铸态Al-Li-Cu合金组织演变和力学性能的影响。Mg和Si含量及其比值（Mg/Si）对凝固过程中的相形成、固溶过程中的溶解行为和时效过程中的析出演化有重要影响。Mg/Si比的增加促进了Mg2Si的形成，抑制了AlLiSi的形成，特别是在Mg/Si比为3时。然而，过量的Mg添加量（>2.4 wt%）会导致严重的晶界偏析，促进低熔点相的形成，如Al2CuMg和Al-Li-Cu-Mg复合相，从而降低了初熔温度，阻碍了固溶处理过程中的完全溶解。Mg和Si含量适中的合金（如5M2S和12M4S合金）富cu相的溶解更有效，而过量Mg和Si含量的合金则保留了较粗的未溶解颗粒，降低了断裂韧性。时效过程中，Mg和Si的加入抑制了θ′析出，促进了T1和纳米级Mg2Si析出的更均匀分布，抑制了δ′-Al3Li的粗化。因此，实现了明显的固溶和沉淀强化。在175℃时效8 h后，5M2S合金的屈服强度达到291 MPa，极限抗拉强度达到381 MPa，伸长率达到3.1%。这些发现阐明了Mg和Si在调整微观组织演变中的协同作用，并为设计高性能铸造Al-Li-Cu合金提供了实用指导。

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引用次数: 0

A protocol for in-situ high resolution strain mapping at elevated temperature 高温下的原位高分辨率应变成像方案

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116119

D. Lunt , A.D. Smith , J.M. Donoghue , I. Alakiozidis , R. Thomas , E.J. Pickering , P. Frankel , M. Carrington , B. Poole , C. Hardie , C. Hamelin , A. Harte

High-resolution digital image correlation (HRDIC) is a well-established technique for mapping local displacements during tensile loading for the quantification of strain localisation at the sub-grain scale using a scanning electron microscope (SEM). This is achieved by the tracking of a nanoscale pattern that is applied to the sample surface by either direct sputtering, thin-film remodelling, or fine nanoparticles. For elevated temperature testing a pattern that is thermally stable is essential. Here, gold remodelling was carried out in a styrene environment, which enables remodelling on corrosion-susceptible materials without oxide formation, followed by a stabilisation heat treatment to fully saturate the growth of the nanospeckles for elevated temperature testing. In this paper, elevated temperature testing refers to uniaxial tensile testing in an SEM at temperatures up to 400 °C. Robust procedures have to date not been established and this paper provides a repeatable process for performing elevated temperature HRDIC. We have developed good practice for acquiring and analysing strain maps with nanoscale resolution at temperature. Systematic error analysis was performed to determine the strain noise by correlating relative to the stabilised and non-stabilised pattern. Plasma cleaning in the SEM was essential to enable low noise measurements by reducing surface contamination during heating. Different detectors were investigated to find the most suitable, where the Everhart-Thornley secondary electron detector exhibited the lowest noise across the temperature range. The method was applied to a ferritic-martensitic steel, where the balance between measurement noise reduction and maximising spatial resolution to fully resolve grain scale deformation features is discussed. Being able to perform these experiments will permit the development and verification of new and novel materials.

高分辨率数字图像相关（HRDIC）是一种成熟的技术，用于绘制拉伸加载过程中的局部位移，用于使用扫描电子显微镜（SEM）在亚晶粒尺度上量化应变局部化。这是通过直接溅射、薄膜重塑或细纳米颗粒对应用于样品表面的纳米级图案进行跟踪来实现的。对于高温测试，热稳定的模式是必不可少的。在这里，金重塑是在苯乙烯环境中进行的，这使得在不形成氧化物的情况下对易腐蚀材料进行重塑，然后进行稳定热处理，使纳米斑点的生长完全饱和，以进行高温测试。在本文中，高温测试是指在高达400°C的温度下，在SEM中进行单轴拉伸测试。迄今为止还没有建立可靠的程序，本文提供了执行高温HRDIC的可重复过程。我们已经开发了在温度下以纳米级分辨率获取和分析应变图的良好实践。系统误差分析是通过相对于稳定和非稳定模式的相关性来确定应变噪声。扫描电镜中的等离子体清洗对于通过减少加热过程中的表面污染来实现低噪声测量至关重要。研究了不同的探测器以寻找最合适的探测器，其中Everhart-Thornley二次电子探测器在整个温度范围内表现出最低的噪声。将该方法应用于铁素体-马氏体钢，讨论了测量噪声降低与最大化空间分辨率之间的平衡，以充分解决晶粒尺度变形特征。能够进行这些实验将允许开发和验证新的和新颖的材料。

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引用次数: 0

Microstructure evolution and failure mechanism of SP2215/Stellite-6 components prepared by laser directed energy deposition during high-temperature service 高温激光定向能沉积制备SP2215/Stellite-6构件的组织演变及失效机理

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116112

Pengcheng Che , Lilin Xie , Shamima Sultana , Nan Wang , Li Yang , Wenjie Zhao , Zhiliang Ning , Jianfei Sun , Shuo Wang , Yongjiang Huang

Additive manufacturing via laser directed energy deposition (L-DED) is an effective method for fabricating advanced coatings to enhance surface wear and corrosion resistance. However, cracking and spallation during high-temperature service of these coatings can significantly reduce their service life. This study systematically investigates the microstructural evolution and thermomechanical coupling behavior at the SP2215/Stellite-6 interface, where Stellite-6, a cobalt-based alloy, was deposited via L-DED onto austenitic stainless steel 22Cr15Ni3.5CuNbN (SP2215). L-DED-fabricated SP2215/Stellite-6 samples underwent prolonged thermal exposure at 650 °C for up to 5000 h to simulate service conditions. The decomposition of M₂₃C₆ along grain boundaries within Stellite-6 accelerates the diffusion of Cr and C atoms, leading to the reprecipitation and Ostwald ripening of M₂₃C₆ carbides along the SP2215/Stellite-6 interface and within Stellite-6 grains. These carbides act as crack initiation sites, promoting crack propagation and reducing fracture strength at both the interface and within the deposited Stellite-6 layer. The interfacial shear strength and impact absorbed energy decreased from 435.2 MPa and 82.8 J in as-built condition (0 h) to 112 MPa and 5.9 J after 5000 h high-temperature service, respectively. These findings can provide critical insights into the mechanisms of cracking and spallation failure in L-DED-fabricated cobalt-based alloy coatings under long-term and high-temperature service.

通过激光定向能沉积（L-DED）的增材制造是制造先进涂层以提高表面磨损和耐腐蚀性的有效方法。然而，在高温使用过程中，这些涂层的开裂和剥落会大大降低其使用寿命。本研究系统地研究了在22cr15ni3.5 5cunbn （SP2215）奥氏体不锈钢表面通过L-DED沉积钴基合金Stellite-6的SP2215/Stellite-6界面的显微组织演变和热-力学耦合行为。l - d制造的SP2215/Stellite-6样品在650°C下长时间热暴露长达5000小时，以模拟使用条件。M23C6沿晶界的分解加速了Cr和C原子的扩散，导致M23C6碳化物沿SP2215/Stellite-6界面和Stellite-6晶粒内的再沉淀和奥斯特瓦尔德成熟。这些碳化物作为裂纹起裂部位，促进裂纹扩展，降低沉积的Stellite-6层界面和内部的断裂强度。高温工作5000 h后，界面抗剪强度和冲击吸收能分别从原状（0 h）的435.2 MPa和82.8 J降低到112 MPa和5.9 J。这些发现可以为长期高温使用下l - d制造的钴基合金涂层的开裂和剥落失效机制提供重要见解。

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引用次数: 0

Heat resistance performance and degradation mechanisms of the RR350 AlCu alloy in medium-high temperature environments (250–400°C) 中高温环境下（250 ~ 400℃）RR350 AlCu合金耐热性能及降解机理研究

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116113

Hong He , Yepeng Zhang , Sinian Wan , Xiong Tao , Ke Li , Ruiqing Lu , Xinghao Gao , Daijun Wang , Fulin Jiang , Wei Li , Wenkang Zhang

This study investigates the heat resistance performance of the RR350 AlCu alloy under medium-high service temperatures of 250–400 °C. The growth, coarsening, and phase transformations of different precipitates were analyzed, and the corresponding mechanisms were discussed. Experimental results show that the T6-treated RR350 alloy undergoes significant hardness degradation during the heat resistance testing processes. Increasing the testing temperature accelerates greatly the precipitate phase transformation from θ″ to θ' and coarsening both of them. The θ″ phase shows low coarsening rate but is not stable with a rapid transforming into the θ' phase. While the θ' phase is relatively stable, with its coarsening rate gradually decreasing as the heat resistance test progresses. However, when the testing temperature exceeds 350 °C, the θ' phase begins to dissolve, leading to a rapid decline in sample hardness. Even though the samples were previously peak aged at different artificial aging temperature, they exhibit similar hardness softening behavior at the same heat resistance testing temperature, due to two main reasons: (1) weak stability of the θ″ phase which leads to a rapid transformation into the θ' phase within 0.5 h of thermal exposure, making the influence of the remaining θ″ phase negligible in the subsequent process; (2) at higher heat resistance testing temperatures, the accelerated coarsening rate of the θ' phase reduces the size differences between the θ' phase originated from different aging heat treatments and the newly formed during thermal exposure. The whole results prove that the RR350 alloy shows good heat resistance performance up to 400 h when the temperature is not higher than 300 °C and a relatively shorter time of about 100 h in the temperature range of 350–400 °C.

研究了RR350 AlCu合金在250 ~ 400℃中高温下的耐热性能。分析了不同析出相的生长、粗化和相变过程，并探讨了相应的机理。实验结果表明，经t6处理的RR350合金在耐热性测试过程中出现了明显的硬度下降。升高试验温度可显著加速析出相由θ″向θ′转变，并使两者粗化。θ″相粗化速率较低，但不稳定，向θ′相转变较快。而θ′相相对稳定，随着耐热性试验的进行，其粗化速率逐渐降低。但当测试温度超过350℃时，θ′相开始溶解，导致试样硬度迅速下降。尽管在不同的人工时效温度下进行了峰值时效处理，但在相同的耐热性测试温度下，试样表现出相似的硬度软化行为，主要有两个原因：(1)θ″相的稳定性较弱，在热暴露0.5 h内迅速转变为θ′相，使得剩余的θ″相的影响可以忽略不计；(2)在较高的耐热性测试温度下，θ′相粗化速率的加快减小了不同时效热处理产生的θ′相与热暴露时新形成的θ′相之间的尺寸差异。整体结果表明，在温度不高于300℃时，RR350合金耐热时间可达400 h，在350 ~ 400℃温度范围内耐热时间较短，约为100 h。

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引用次数: 0

Breaking the room-temperature coercivity record via multiphase microstructure in SmCoFe2NiB ribbons 通过SmCoFe2NiB带的多相显微结构打破了室温矫顽力记录

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116109

Shu Wang , Ji-Bing Sun , Xiang Chi , Hu-Hu Su , Tie-Bao Wang , Zhi-Xia Xiao , Ying Zhang

Building upon our previous discovery that the SmCo_1.6Fe_1.6Ni_0.8B composition exhibits a high coercivity of 84.3 kOe after annealing at 850 °C for 30 min [Nat. Commun. 15, 10158 (2024)], this study conducts a dedicated investigation into the effects of annealing temperature and time on another SmCoFe₂NiB alloy. A record room-temperature coercivity of 100.8 kOe is achieved in its ribbons annealed at 760 °C for 30 min, surpassing the previous best value for this alloy system. Correspondingly, a well-defined multiphase microstructure composed of stripe-shaped and equiaxed nanograins is revealed. The ultrahigh coercivity is attributed to the high magnetocrystalline anisotropy of the stripe-shaped Sm-Co-B nanograins, whereas interphase boundaries and planar defects serve only as barriers to domain-wall motion. These findings provide not only a practical route to enhance magnetic properties but also a deeper understanding of the microstructural evolution mechanisms in multiphase SmCo₄B-based magnets.

基于我们之前的发现，SmCo1.6Fe1.6Ni0.8B组合物在850°C退火30 min后显示出84.3 kOe的高矫顽力[Nat. comm . 15,10158(2024)]，本研究对退火温度和时间对另一种SmCoFe2NiB合金的影响进行了专门的研究。在760°C退火30分钟后，其带的室温矫顽力达到了100.8 kOe，超过了该合金系统之前的最佳值。相应的，由条纹状和等轴状纳米颗粒组成的多相微观结构被清晰地定义。超高矫顽力是由于条形Sm-Co-B纳米颗粒的高磁晶各向异性，而相界面和平面缺陷仅作为畴壁运动的障碍。这些发现不仅为提高磁性能提供了一条实用的途径，而且对多相smco4b基磁体的微观结构演化机制也有了更深入的了解。

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引用次数: 0

Revisiting the influence of Cr and Ti on the γ'-Ni₃Al phase dissolution and precipitation kinetics: A combined study using diffusion couples, CALPHAD, and DFT Cr和Ti对γ′-Ni₃Al相溶解析出动力学的影响：基于扩散偶、CALPHAD和DFT的联合研究

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116117

Xinyu Gao , Chao Yuan

In Ni-based superalloy system, the alloying element Cr mainly enters the γ-matrix for solid solution strengthening, and improves the oxidation resistance and thermal corrosion resistance, while the Ti element mainly enters the γ’-Ni₃Al phase to undertake precipitation strengthening. This study delves into the temporal evolution behaviors of the γ' phase solution and coarsening in the Ni-Al-X (X = Cr, Ti) system. Experimentally, incorporating low concentrations of Cr and Ti elements has a significant preventing effect on the γ’ → γ phase transition. Based on thermodynamic and kinetic theories, the potential mechanism of alloy elements preventing phase transition has been clarified. Specifically, the addition of Cr and Ti leads to a notable increase in the driving force ΔG required for the phase transition to occur, as evidenced by changes in Gibbs free energy calculated using the CALPHAD methodology. Computationally, the incompressibility of Al induced by the doping of Cr and Ti plays a crucial role in preventing the formation of the newly forming γ phase. Furthermore, during low-temperature aging, different forms of γ’-Ni₃Al phase are precipitated in the newly forming γ phase region, and their morphology, size, and distribution are closely related to the precipitation location. The precipitation process of the Ni₃Al phase depends on the diffusivity of Ni and Al atoms, while its growth behavior is governed by the diffusion mechanism of Al atoms.

在ni基高温合金体系中，合金元素Cr主要进入γ-基体进行固溶强化，提高了合金的抗氧化性和抗热腐蚀能力，而Ti元素主要进入γ′-Ni3Al相进行析出强化。本文研究了Ni-Al-X （X = Cr, Ti）体系中γ′相溶液和粗化的时间演化行为。实验结果表明，低浓度的Cr和Ti元素对γ′→γ相变具有显著的抑制作用。基于热力学和动力学理论，阐明了合金元素阻止相变的潜在机理。具体来说，Cr和Ti的加入导致相变发生所需的驱动力ΔG显著增加，这可以通过使用CALPHAD方法计算的吉布斯自由能的变化来证明。计算表明，Cr和Ti掺杂导致Al的不可压缩性对阻止新形成的γ相的形成起着至关重要的作用。低温时效过程中，在新形成的γ相区析出不同形态的γ′-Ni3Al相，其形态、大小和分布与析出位置密切相关。Ni3Al相的析出过程取决于Ni和Al原子的扩散率，而其生长行为受Al原子扩散机制的支配。

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引用次数: 0

Subgrain-boundary induced improvement mechanism in strength, ductility and electrical conductivity of Cu-Cr-Ag-Mg-Sn alloy Cu-Cr-Ag-Mg-Sn合金的亚晶界诱导强度、延展性和电导率提高机制

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116114

Xingyu Xiao , Zhilei Wang , Qi Yang , Jianxin Xie

High-performance copper alloys with an optimal combination of strength, electrical conductivity, and ductility are increasingly demanded for next-generation electronics. Herein, a subgrain-boundary-mediated strategy is proposed to overcome the typical strength–ductility–conductivity conflict in a Cu–Cr–Ag–Mg–Sn alloy. Using a tailored thermomechanical process combing cold rolling and short-time solid solution treatment, high-density subgrain boundaries were introduced. These subgrain boundaries promote dense nanoscale Cr-rich precipitates, which serve as both dislocation sources and obstacles, enabling simultaneous gains in strength and electrical conductivity. Moreover, during deformation, they interact with dislocations, not only inhibiting dislocation slip to strengthen the alloy but also enabling dislocation multiplication and storage to improve ductility. This work establishes subgrain boundary engineering as a viable design principle for advanced precipitation-strengthened copper alloys with excellent performance.

高性能铜合金具有强度、导电性和延展性的最佳组合，对下一代电子产品的需求日益增加。本文提出了一种亚晶界介导的策略来克服Cu-Cr-Ag-Mg-Sn合金中典型的强度-塑性-电导率冲突。采用冷轧与短时固溶相结合的量身定制的热处理工艺，引入了高密度亚晶界。这些亚晶界促进了致密的纳米级富cr析出物，这些析出物既是位错源，也是障碍，使强度和导电性同时提高。此外，在变形过程中，它们与位错相互作用，不仅抑制位错滑移以增强合金，而且使位错增殖和储存以提高塑性。本研究为亚晶界工程设计提供了一种可行的设计原则，可用于性能优异的先进析出强化铜合金。

引用次数: 0

Mechanical behavior and microstructure evolution of spheroidized-annealed GCr15 bearing steel under dynamic loading 动态加载下球化退火GCr15轴承钢力学行为及组织演变

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116110

Shicheng Liang , Bo Gao , Yang Liu , Caiyi Liu , Chengwu Zheng , Lichi Tian , Pei Wang , Yan Peng , Dianzhong Li

In this study, the intrinsic correlation between dynamic mechanical behavior and microstructural evolution of spheroidized-annealed GCr15 bearing steel with a ferrite-carbide dual-phase structure has been investigated under high strain rates (3000–7000 s⁻¹) and wide temperature ranges (20–650 °C). To more accurately characterize the dynamic mechanical response，the conventional TANH-Johnson-Cook (TANH-JC) constitutive model is optimized by incorporating the actual strain rate and the softening effect arising from adiabatic temperature rise observed in Split Hopkinson Pressure Bar (SHPB) experiments. This modification significantly improves the model's prediction accuracy. Furthermore, the coupling mechanisms among deformation parameters, dynamic recrystallization of ferrite, and carbide evolution are elucidated using multi-scale characterization techniques. Continuous dynamic recrystallization (CDRX) is identified as the primary grain refinement mechanism in the ferrite matrix, supplemented by particle-stimulated nucleation dynamic recrystallization (PSNDRX). The evolution of carbides is governed by the synergistic interaction of temperature and strain rate. The atomic diffusion capacity is enhanced with increased temperature, while numerous additional rapid diffusion pathways are introduced through its coupling with plastic deformation. These factors promote the dissolution of small carbides and the coarsening of large carbides. When thermal effects dominate, significant carbide dissolution weakens the Zener pinning effect, leading to coarsening of recrystallized grains. These microstructural evolution characteristics collectively govern the macroscopic mechanical response through three primary strengthening mechanisms: grain boundary strengthening, dislocation strengthening, and precipitation strengthening. This study provides practical engineering guidance for optimizing the turning process of material in subsequent machining operations.

本文研究了铁素体-碳化物双相组织球化退火GCr15轴承钢在高应变速率（3000 ~ 7000 s−1）和宽温度范围（20 ~ 650℃）下动态力学行为与微观组织演变的内在相关性。为了更准确地表征材料的动态力学响应，将传统的TANH-Johnson-Cook （TANH-JC）本构模型纳入实际应变速率和Split Hopkinson压杆（SHPB）实验中观察到的绝热温升引起的软化效应，对其进行了优化。这一修正显著提高了模型的预测精度。此外，利用多尺度表征技术阐明了形变参数、铁素体动态再结晶和碳化物演化之间的耦合机制。连续动态再结晶（CDRX）是铁素体基体晶粒细化的主要机制，其次是颗粒激发成核动态再结晶（PSNDRX）。碳化物的演化受温度和应变速率的协同作用支配。原子扩散能力随着温度的升高而增强，同时通过其与塑性变形的耦合引入了许多额外的快速扩散途径。这些因素促进了小碳化物的溶解和大碳化物的粗化。当热效应占主导地位时，显著的碳化物溶解削弱了齐纳钉钉效应，导致再结晶晶粒变粗。这些微观组织演化特征通过晶界强化、位错强化和析出强化三种主要强化机制共同控制宏观力学响应。该研究为后续加工中材料车削工艺的优化提供了实际的工程指导。

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引用次数: 0

Enhanced strength and ductility by optimizing B2-NiAl precipitation shape in ferritic alloys 通过优化铁素体合金中B2-NiAl的析出形状来提高强度和延展性

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-03 DOI: 10.1016/j.matchar.2026.116118

Yuanchen Liang , Peng Zhang , Yongwei Wang , Ye Liu , Ming Li , Lin Zhang , Xuanhui Qu

B2-NiAl strengthened ferritic alloys show promising potential for high-temperature applications, but their room-temperature brittleness under high precipitate volume fraction remains a major limitation. To overcome this shortcoming, a ferritic alloy with two variants was produced by rationally designing the austenite phase region and altering the sequence of solution treatment and hot rolling. The main microstructural difference between the two variants lies in the morphology of B2 phase, while other characteristics remain largely consistent. Mechanical tests demonstrated that the alloy with 30.4 vol% of spherical B2 precipitates exhibits higher yield strength (1104 ± 46 MPa vs. 1058 ± 16 MPa), tensile strength (1725 ± 35 MPa vs. 1597 ± 16 MPa), and uniform elongation (6.5 ± 0.2% vs. 4.8 ± 0.3%) compared to the variant containing rod-shaped precipitates. Further crystal plasticity finite element modeling confirmed that the high symmetry and isotropy of the spherical B2 precipitates promote stress delocalization and higher strain gradients, thereby enhancing back-stress strengthening and work hardening capacity. These findings align with observations of deformed microstructures, which revealed higher dislocation density and uniformly distributed nanopores in the alloy with spherical B2 precipitates. Calculations of the theoretical yield strength indicated that the strength improvement primarily stems from the stronger back-stress strengthening effect induced by the spherical B2 phase.

B2-NiAl强化铁素体合金具有良好的高温应用前景，但其在高析出物体积分数下的室温脆性仍然是其主要局限性。为克服这一缺点，通过合理设计奥氏体相区，改变固溶处理和热轧顺序，制备了两种变体的铁素体合金。两种变体的主要显微组织差异在于B2相的形貌，而其他特征基本一致。力学试验表明，与含有棒状析出相的合金相比，含有30.4 vol%球状B2析出相的合金具有更高的屈服强度（1104±46 MPa vs. 1058±16 MPa）、抗拉强度（1725±35 MPa vs. 1597±16 MPa）和均匀伸长率（6.5±0.2% vs. 4.8±0.3%）。进一步的晶体塑性有限元模拟证实，球状B2析出物的高对称性和各向同性促进了应力离域和更高的应变梯度，从而增强了背应力强化和加工硬化能力。这些发现与变形显微组织的观察结果一致，表明具有球形B2析出物的合金中存在更高的位错密度和均匀分布的纳米孔。理论屈服强度的计算表明，强度的提高主要源于球形B2相引起的更强的背应力强化效应。

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引用次数: 0

Simultaneously improving coercivity and temperature coefficient of remanence of sintered Nd-Fe-B magnets through Co/(TbAl) grain boundary diffusion 同时通过Co/(TbAl)晶界扩散提高烧结Nd-Fe-B磁体的矫顽力和残余温度系数

IF 5.5 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2026-02-02 DOI: 10.1016/j.matchar.2026.116106

Weihao Jiang , Jingzhen Zhou , Guodong Li , Yue Wang , Chengcan Li , Da Li , Yuan Xia , Yi Xu

In this work, Co/TbAl coatings with controlled Co concentration are synthesized via direct current magnetron sputtering (DCMS) in a multilayer configuration and employed as grain boundary diffusion sources for simultaneous improvement of intrinsic coercivity (H_cj) and temperature coefficient of remanence (α) of the sintered Nd-Fe-B magnet. Results reveal that the Co_38.37Tb_42.66Al_18.97 diffused magnet, prepared by introducing a moderate concentration of Co into the diffusion source, achieves the best comprehensive magnetic properties. Specifically, compared to the original magnet, it demonstrates a significant H_cj enhancement from 12.49 kOe to 18.19 kOe, accompanied by a B_r improvement from 14.44 kGs to 14.76 kGs. Notably, its α is also substantially increased from −0.132%/°C to −0.113%/°C, exhibiting excellent thermal stability. The H_cj enhancement is attributed to the formation of Tb-rich shells possessing high anisotropic fields (H_A), while the improvement in α arises from the formation of RE₂(Fe,Co)₁₄B phases with elevated Curie temperatures. However, in the Co_56.05Tb_28.71Al_15.24 diffused magnet, the excessive Co concentration leads to the agglomeration of Co in grain boundary phases (GBPs), which is attributed to the higher formation energies of (Nd,Tb)₂(Fe_,Co)₁₄B with the increase of Co concentration. Meanwhile, the soft magnetic NdCo₄B possessing plane anisotropy and high melting temperature can be found in the Co-rich triple junction phases (TJPs). It not only acts as the nucleation sites for reversed magnetic domains but also leads to the poor wettability of the GBPs, thereby in turn deteriorating the magnetic properties of diffused magnets.

本文采用直流磁控溅射（DCMS）法制备了Co浓度可控的多层Co/TbAl涂层，并将其作为晶界扩散源，提高了烧结Nd-Fe-B磁体的固有矫顽力（Hcj）和残余温度系数（α）。结果表明，在扩散源中加入适量Co制备的Co38.37Tb42.66Al18.97扩散磁体具有最佳的综合磁性能。与原磁体相比，Hcj从12.49 kOe显著提高到18.19 kOe， Br从14.44 kGs提高到14.76 kGs， α从- 0.132%/°C显著提高到- 0.113%/°C，具有良好的热稳定性。Hcj的增强是由于形成了具有高各向异性场（HA）的富tb壳层，而α的增强是由于在居里温度升高的情况下形成了RE2(Fe,Co)14B相。而在Co56.05Tb28.71Al15.24扩散磁体中，过量的Co浓度导致Co在晶界相（GBPs）中聚集，这是由于（Nd,Tb）2(Fe,Co)14B的形成能随着Co浓度的增加而升高。同时，在富钴三结相（TJPs）中发现了具有平面各向异性和高熔融温度的软磁NdCo4B。它不仅作为反磁畴的成核位点，而且还导致GBPs的润湿性差，从而反过来恶化扩散磁体的磁性能。

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