International Journal of Plasticity最新文献_第8页

A new strategy for fabricating Mg-Al alloys with excellent strength-ductility synergy via pulse-coupled wire-arc directed energy deposition 脉冲耦合线弧定向能沉积制备具有优异强度-延展性协同效应的Mg-Al合金的新策略

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-14 DOI: 10.1016/j.ijplas.2025.104550

Yukang An , Enyu Guo , Diyang Xia , Shuo Yin , Zhirou Zhang , Wuyue Zheng , Zongning Chen , Huijun Kang , Tongmin Wang

Wire-arc directed energy deposition (W-DED) is a cost-effective additive manufacturing technology increasingly applied to the fabrication of magnesium alloy components. However, AZ-series magnesium alloys fabricated by conventional DED suffer from inadequate properties and premature failure due to stress concentration caused by coarse structure and high fraction of porosity. In this work, a high-energy pulsed arc is introduced into the W-DED of AZ31B alloy, and its effects on porosity, microstructure, mechanical properties, and deformation damage behavior are comprehensively investigated. The pulsed-coupled DED (CMT+P) process significantly enhances component densification while refining grains and precipitates by intensifying solidification dynamics and modifying solute redistribution. The AZ31B alloy fabricated by CMT+P process exhibits a superior strength-ductility synergy, with ultimate tensile strength of 262 ± 1.5 MPa along BD and 267 ± 2 MPa along TD accompanied by a total elongation of 24.7 ± 1.8 % and 25.4 ± 1.5 %, respectively. In-situ synchrotron tomography from a novel “primary damage band (PDB)” perspective reveals the competitive relationship between initial and derived pores of deformation behavior. During the progressive damage evolution, the optimized structure crucially suppresses derived pore nucleation and delays stress accumulation to enhance damage tolerance and promote uniform plastic deformation. This work provides a new strategy for fabricating high-performance Mg-Al DED components that combine high performance with superior damage resistance.

电弧定向能沉积（W-DED）是一种经济高效的增材制造技术，越来越多地应用于镁合金部件的制造。然而，传统DED法制备的az系列镁合金由于结构粗大、孔隙率高，导致应力集中，导致性能不理想、过早失效。本文将高能脉冲电弧引入AZ31B合金的W-DED中，全面研究了高能脉冲电弧对AZ31B合金的孔隙率、微观组织、力学性能和变形损伤行为的影响。脉冲耦合DED （CMT+P）工艺通过强化凝固动力学和改变溶质再分布来细化晶粒和析出相，显著提高了组分致密化程度。CMT+P工艺制备的AZ31B合金表现出优异的强度-塑性协同效应，沿双轴拉伸强度为262±1.5 MPa，沿双轴拉伸强度为267±2 MPa，总伸长率分别为24.7±1.8 %和25.4±1.5 %。从一种新颖的“初级损伤带（PDB）”角度出发的原位同步加速器断层扫描揭示了变形行为的初始和衍生孔隙之间的竞争关系。在损伤演化过程中，优化后的结构对孔隙成核和应力积累起到关键抑制作用，从而提高损伤容限，促进均匀塑性变形。这项工作为制造高性能Mg-Al DED组件提供了一种新的策略，该策略将高性能与优异的抗损伤性结合起来。

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引用次数: 0

Ascertaining the plastic deformation mechanisms of polycrystalline extruded Zn through in situ SEM/EBSD mechanical tests 通过原位SEM/EBSD力学试验确定多晶挤压锌的塑性变形机理

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-11 DOI: 10.1016/j.ijplas.2025.104548

Alireza Rezaei , Nafiseh Mollaei , Maral Sarebanzadeh , Biaobiao Yang , Seyed Mahmood Fatemi , Javier LLorca

The plastic deformation micro-mechanisms of extruded pure Zn deformed in tension along the extrusion direction were investigated by means of in situ scanning electron microscopy (SEM) integrated with electron back-scatter diffraction (EBSD). Plastic deformation began with the activation of 〈a〉 basal slip in grains with the highest Schmid factor while, the incompatibility of deformation between neighbour grains was accommodated by grain boundary sliding. The geometrically necessary dislocation density increased sharply from 1.53 × 10¹³ m⁻² to 9.03 × 10¹³ m⁻² when applied strain reached 6.7%, and this increase coincides with the strong initial strain hardening region. The incompatibility of deformation between neighbour grains was accommodated by grain boundary sliding at strains above 3.3%, which somehow limited the strain hardening rate. Evidence of 〈c + a〉 pyramidal II slip was also found through slip trace analysis from the early stages of deformation, i.e. 1.6% strain, but it was always limited to a small fraction of suitably oriented grains. Moreover, transmission electron microscopy (TEM) observations showed that many 〈c + a〉 pyramidal dislocations were dissociated into the basal plane and became sessile. {

10 \overline{1} 2

}<

10 \overline{1} \overline{1}

> compression twins were nucleated at 3.3% strain and the fraction of grains undergoing twinning as well as the area fraction of twins increased proportionally to the applied strain. Twinning was favoured by the fiber texture and the twin variant with the highest Schmid factor was primarily activated in each grain. The contribution of twinning to the total strain was limited (around 11% when the applied strain was 16.7%). The strain hardening rate decreased sharply beyond 6.7% and the hardening contribution of basal slip was balanced by grain boundary sliding and compression twinning. Finally, a high fraction of sub-grain boundaries that trigger recrystallization at larger strains was found at 16.7%. These observations reveal the sequence and interaction of plastic deformation mechanisms in Zn, which may help design novel Zn alloys with improved mechanical properties.

采用原位扫描电子显微镜（SEM）和电子背散射衍射（EBSD）相结合的方法，研究了挤压纯锌沿挤压方向拉伸变形的微观塑性变形机理。塑性变形始于施密德系数最高的晶内基底滑移的激活，而相邻晶粒之间变形的不相容则由晶界滑移来调节。当应变达到6.7%时，几何上必要的位错密度从1.53 × 1013 m⁻²急剧增加到9.03 × 1013 m⁻²，这种增加与强的初始应变硬化区一致。当应变大于3.3%时，晶界滑移调节了相邻晶粒间变形的不相容，这在一定程度上限制了应变硬化速率。变形初期的滑移迹分析也发现了<；c+a>； II型锥体滑移的证据，即1.6%的应变，但始终局限于一小部分取向合适的晶粒。此外，透射电镜观察显示，许多锥体位错被解离到基面上并成为无柄。{101¯2}<101¯1¯>；压缩孪晶在3.3%应变下成核，孪晶的晶粒比例和孪晶的面积比例随应变的增加而成比例增加。纤维织构有利于孪晶形成，施密德因子最高的孪晶变异主要在各粒中被激活。孪生对总应变的贡献是有限的（当施加应变为16.7%时约为11%）。应变硬化率急剧下降至6.7%以上，基底滑移的硬化作用被晶界滑移和压缩孪晶所平衡。最后，16.7%的亚晶界在较大的应变下触发再结晶。这些观察结果揭示了Zn中塑性变形机制的顺序和相互作用，这可能有助于设计具有更好力学性能的新型Zn合金。

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引用次数: 0

Nonlinear chemomechanical modeling of hydrogen diffusion in super duplex stainless steel and comparison with x-ray diffraction measurements 超级双相不锈钢中氢扩散的非线性化学力学建模及与x射线衍射测量的比较

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-11 DOI: 10.1016/j.ijplas.2025.104546

David Lindblom , Menghao Liu , Jinshan Pan , Robin Woracek , Carl F.O. Dahlberg

A coupled hydrogen (H) diffusion and higher-order strain gradient plasticity model is used to predict H localization in the ferrite (

α

) and austenite (

γ

) phases of super duplex steel under plane stress conditions. The geometry and finite element (FE) mesh are derived from optical micrograph images of the phase morphology, ensuring a realistic representation of the alloy’s microstructure. The model highlights the role of individual phases in coupled diffusion–mechanics interactions and demonstrates that the phase morphology significantly impacts the localization of H in the material. The results indicate that plastic strains in the ferrite phase exert a much greater influence on the spatial distribution of H than in the austenite phase. Finally, results of the model compare well with in situ X-ray diffraction (XRD) measurements of the temporal evolution of the strain induced by H charging. These findings provide valuable insight for future alloy design strategies aimed at mitigating H localization and preventing embrittlement.

采用氢(H)扩散和高阶应变梯度塑性耦合模型预测了平面应力条件下超级双相钢铁素体（αα）和奥氏体（γγ）相中H的局部化。几何和有限元（FE）网格来源于相形态的光学显微图像，确保了合金微观结构的真实表现。该模型强调了单个相在耦合扩散力学相互作用中的作用，并表明相形态显著影响H在材料中的局部化。结果表明，铁素体相的塑性应变对H的空间分布的影响远大于奥氏体相。最后，该模型的结果与原位x射线衍射（XRD）测量的H电荷引起的应变的时间演变结果进行了比较。这些发现为未来旨在减轻H局部化和防止脆化的合金设计策略提供了有价值的见解。

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引用次数: 0

A non-isothermal fractional consistency two-surface viscoplasticity model for gas hydrate-bearing sediments 含天然气水合物沉积物非等温分数稠度双表面粘塑性模型

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-10 DOI: 10.1016/j.ijplas.2025.104547

Wei Cheng, Zhen-Yu Yin

Gas hydrate-bearing sediments (GHBS), recognized as an emerging and highly promising unconventional energy resource, exhibit pronounced rate-, temperature-, and pore pressure-dependent mechanical behaviors that have been inadequately addressed or frequently overlooked in existing constitutive modeling frameworks. In this paper, a novel non-isothermal two-surface elasto-viscoplastic model is proposed based on the fractional consistency viscoplasticity and bounding surface theory to capture the key mechanical behaviors of GHBS under varying loading conditions. Specifically, a modified isotach viscosity formulation is first extended to account for hydrate conditions, with the creep coefficient expressed as an exponential function of hydrate saturation. Secondly, a two-surface (loading and yield surfaces) framework is formulated, integrating multifactorial viscoplastic hardening mechanisms, namely isotropic hardening, progressive hardening, and deviatoric degradation, along with a Caputo-formed non-orthogonal viscoplastic flow rule. Then, employing the consistency condition of the loading surface, an incremental constitutive relation is rigorously formulated to explicitly relate stress, strain, strain rate, temperature, pore pressure, and hydrate saturation. Finally, validation against experimental data demonstrates the model’s excellent capability to simulate mechanical behaviors under complex time-dependent stress paths. This robust, rate-dependent constitutive framework provides a fundamental basis for subsequent advancements aimed at incorporating a broader spectrum of pertinent factors, such as hydrate dissociation, extended temperature ranges, multi-component effects, and particle crushing, etc.

天然气水合物沉积物（GHBS）被认为是一种新兴的、非常有前途的非常规能源资源，它表现出明显的速率、温度和孔隙压力相关的力学行为，这些行为在现有的本构模型框架中没有得到充分的解决，或者经常被忽视。本文基于分数一致性粘塑性和边界面理论，提出了一种新的非等温双面弹粘塑性模型，以捕捉不同加载条件下GHBS的关键力学行为。具体来说，首先将修正的等黏度公式推广到水合物条件，将蠕变系数表示为水合物饱和度的指数函数。其次，建立了两面（加载面和屈服面）框架，整合了各向同性硬化、渐进硬化和偏差退化等多因素粘塑性硬化机制，以及caputo形成的非正交粘塑性流动规律。然后，利用加载面一致性条件，严格建立增量本构关系，明确地将应力、应变、应变率、温度、孔隙压力和水合物饱和度联系起来。最后，对实验数据的验证表明，该模型具有良好的能力，可以模拟复杂的随时间变化的应力路径下的力学行为。这种稳健的、速率相关的本构框架为随后的进展提供了基础，旨在纳入更广泛的相关因素，如水合物解离、延长的温度范围、多组分效应和颗粒破碎等。

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引用次数: 0

Data-inspired atomic environment-dependence of vacancy formation energy in high-entropy alloys 高熵合金中空位形成能对原子环境的依赖

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-05 DOI: 10.1016/j.ijplas.2025.104545

Fusheng Tan , Xin Liu , Xuefeng Liang , Yinan Cui

Vacancy properties in High-entropy alloys (HEAs) play a critical role in governing high-temperature microstructural stability, yet the fundamental relationship between Vacancy Formation Energy (VFE) and heterogeneous Local Atomic Environments (LAE) in HEAs remains far from well understood, owing to the complex and heterogeneous nature of LAE. To address this, we developed an interpretable machine learning framework integrating high-throughput molecular dynamics simulations and physics-informed features. Using CoNiCrFeMn as model system, our approach achieves exceptional prediction accuracy (R² = 0.98) for VFE. It is found that the LAE within the first-nearest-neighbor shell around vacancy dominates VFE variations, and the local atomic spatial ordering exerts influence on VFE comparable in magnitude to local chemical composition. Based on the designated LAE descriptor, namely multilevel element pair probability, and feature analysis-guided physics interpretation, we identify for the first time the physical origin of LAE-mediated VFE as the synergistic strong/weak-bond elements competition and lattice distortion effects. Specifically, coexisting strong-bond (e.g., Ni) and weak-bond (e.g., Mn) atoms in 1NN shell around central vacancy drive offsetting displacements through lattice distortion, dynamically tailoring VFE. The mechanism explains anomalously high lattice distortion and elevated vacancy concentrations observed in Mn-containing CoNiCrFeMn HEAs, and further enables a strategy for enhancing vacancy stability via annealing-induced elemental aggregation. These results establish a theoretical framework for defect engineering in the design of complex solid-solution alloys.

高熵合金（HEAs）的空位性质在高温显微组织稳定性中起着至关重要的作用，但由于高熵合金中空位形成能（VFE）与非均相局部原子环境（LAE）的复杂性和非均相性，空位形成能（VFE）与非均相局部原子环境（LAE）之间的基本关系尚不清楚。为了解决这个问题，我们开发了一个可解释的机器学习框架，集成了高通量分子动力学模拟和物理信息功能。使用CoNiCrFeMn作为模型系统，我们的方法对VFE的预测精度很高（R² = 0.98）。发现空位周围第一近邻壳层内的LAE主导着VFE的变化，局域原子空间排序对VFE的影响程度与局域化学成分相当。基于指定的LAE描述符，即多层元素对概率，以及特征分析指导的物理解释，我们首次确定了LAE介导的VFE的物理起源是强/弱键元素竞争和晶格畸变效应的协同作用。具体来说，围绕中心空位的1NN壳层中共存的强键（如Ni）和弱键（如Mn）原子通过晶格畸变驱动偏移位移，动态地调整VFE。该机制解释了在含锰的CoNiCrFeMn HEAs中观察到的异常高晶格畸变和高空位浓度，并进一步实现了通过退火诱导元素聚集来增强空位稳定性的策略。这些结果为复杂固溶合金缺陷工程设计提供了理论框架。

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引用次数: 0

Shock-induced hierarchical plastic deformations in high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C at high strain rate 高熵（Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2）C在高应变速率下冲击诱发的分层塑性变形

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-05 DOI: 10.1016/j.ijplas.2025.104543

Lanxi Feng , Wanghui Li , Wenxuan Tang , Zhuochen Chen , Xiaoqing Zhang , Yilun Xu , Guglielmo Vastola , Fu-Zhi Dai , Yong-Wei Zhang , Xiaohu Yao

Conventional ceramics have ultra-high strength but often lack plasticity. The high-entropy carbide ceramics (HECCs) offer a new perspective to enhance the plasticity of ceramics, which may extend their applicability as components operating under extreme conditions. However, there still lacks research on the dynamic behavior of HECCs, causing a poor understanding of their plastic response to dynamic loading. In this work, the dynamic behavior of a high-entropy ceramic (Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C (denoted as HEC) under shock compression is investigated, for the first time, by the plate impact experiments with two-stage gas gun and molecular dynamics simulations utilizing a deep learning potential based on accurate first-principles data. With increasing shock pressure, HEC undergoes a pronounced elastic-plastic transition characterized by the formation of multiple plastic deformation bands, local phase transition and amorphization, which involve the activations of

< 1 \bar{1} 0 > {1 1 0}

and

< 1 \bar{1} 0 > {1 1 1}

slip systems simultaneously. The local lattice distortions in HEC are found to influence the behavior of dislocation propagation during shock compression. Instead of following predefined paths, dislocations tend to deviate at the propagation front, resulting in the formation of vacancies. Our findings reveal the hierarchical plastic deformation mediated by multi-competing mechanisms in HEC under extreme conditions, suggesting a promising strategy for achieving HECCs that are both strong and ductile.

传统陶瓷具有超高的强度，但往往缺乏可塑性。高熵碳化物陶瓷（HECCs）为提高陶瓷的可塑性提供了一个新的视角，可以扩展其作为极端条件下工作的部件的适用性。然而，对于hecc的动力行为研究仍然缺乏，导致对其在动荷载下的塑性响应的理解较差。在这项工作中，首次通过两级气枪板冲击实验和基于精确第一原理数据的深度学习潜力的分子动力学模拟，研究了高熵陶瓷（Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2）C（记为HEC）在冲击压缩下的动态行为。随着冲击压力的增加，HEC发生了明显的弹塑性转变，其特征是形成多个塑性变形带，局部相变和非晶化，这涉及<；1ࣥ1 0>；{11 10}和<；1ࣥ1 0>；{11 11}滑移体系的同时激活。在激波压缩过程中，发现HEC中的局部晶格畸变会影响位错的扩展行为。而不是按照预定的路径，位错往往偏离在传播前沿，导致空位的形成。我们的研究结果揭示了极端条件下HEC中由多种竞争机制介导的分层塑性变形，为实现既强又延展性的HEC提供了一个有希望的策略。

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引用次数: 0

A coupled crystal plasticity-phase field framework for anisotropic fracture in Ni-based single crystals 镍基单晶各向异性断裂的晶体塑性-相场耦合框架

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-05 DOI: 10.1016/j.ijplas.2025.104541

H.T. Li , X.M. Wang , H. Cheng , Z.L. Ding , S.Y. Sun , W.Z. Yang , Y. Wang

Crack nucleation, propagation and coalescence in anisotropic Ni-based single crystal superalloys are critical to the durability of aero engines hot-section components. This study develops a coupled crystal-plasticity and phase-field model to capture the fracture behavior for the materials and account for the coupling effects between plasticity and damage. The framework incorporates a fracture toughness degradation function driven by plastic strain energy, directly illustrating the influence of plastic deformation on crack resistance. Additionally, a yield surface degradation function, incorporated into power-law flow theory, accounts for damage-induced strength reduction and prevents numerical instabilities in severely damaged zones. Furthermore, elastoplastic constitutive relations are decomposed into crack-driving and persistent components within a variational framework, addressing tension-compression asymmetry for fracture behavior and satisfying the orthogonality decomposition condition for anisotropic materials. The proposed model is validated through numerical examples, demonstrating its ability to accurately predict experimental results and elucidate the anisotropic fracture processes in Ni-based single crystal superalloys. This work provides a robust framework for understanding and predicting fracture in anisotropic materials, with potential applications for advancing aerospace hot-section component design.

各向异性镍基单晶高温合金裂纹的形核、扩展和聚结对航空发动机热断面部件的耐久性起着至关重要的作用。本研究建立了一种晶体-塑性和相场耦合模型，以捕捉材料的断裂行为，并考虑塑性和损伤之间的耦合效应。该框架包含了由塑性应变能驱动的断裂韧性退化函数，直接说明了塑性变形对抗裂性能的影响。此外，纳入幂律流动理论的屈服面退化函数解释了损伤引起的强度降低，并防止了严重损伤区域的数值不稳定。此外，在变分框架内将弹塑性本构关系分解为裂纹驱动和持久分量，解决了断裂行为的拉压不对称问题，并满足各向异性材料的正交性分解条件。通过数值算例验证了该模型的正确性，表明该模型能够准确预测实验结果，并能很好地解释ni基单晶高温合金的各向异性断裂过程。这项工作为理解和预测各向异性材料的断裂提供了一个强大的框架，具有推进航空航天热截面部件设计的潜在应用。

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引用次数: 0

Molecular dynamics study on the multi-spallation of Ti-6Al-4V titanium alloy caused by non-planar effect of shock wave induced by microscopic interface 微观界面引起的非平面激波效应对Ti-6Al-4V钛合金多重裂裂的分子动力学研究

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-05 DOI: 10.1016/j.ijplas.2025.104542

Qianhua Yang , Yang Yang , Binwen Wang , Yupei Guo , Xiang Chen

The shock-induced multi-spall processes of nanocrystalline titanium alloys were simulated based on molecular dynamics method in this study to reveal the multi-spall damage mechanism caused by non-planar effect of shock wave induced by microscopic interface. The microscopic interface in nanocrystalline titanium alloys caused non-planar effect of shock wave propagation and hindered shock wave propagation. The shapes of non-planar shock wave in nanocrystalline dual-phase titanium alloys were affected by the distribution of second phase grain. Based on the relationship between the evolution law of tensile stress and the nucleation principle of multi-spall voids, it was found that the multi-spall voids nucleated at microscopic interface under tensile stress generated by the encounter between the secondary reflected wave and the reflected wave for the first time. The non-uniform distribution of tensile stress generated by the encounter between the non-uniform propagation reflected waves led to the non-uniform distribution of multi-spall voids at microscopic interface. The increase of dislocation density caused by second phase grain hindered the secondary void nucleation in nanocrystalline dual-phase titanium alloys, resulting in the difference in secondary void nucleation between nanocrystalline single-phase titanium alloy and nanocrystalline dual-phase titanium alloys. The damage rate (

\dot{D}

) at the spall stage and strain rate (

\dot{ε}

) at the shock stage were positively correlated and followed the relationship:

\dot{D} = a {\dot{ε}}^{b}

(

a

and

b

were fitting parameters and related to the microstructure of material and shock conditions). The multi-voids still nucleated at microscopic interfaces and the intergranular spall occurred in nanocrystalline titanium alloys although the shock velocity increased.

本研究基于分子动力学方法对纳米晶钛合金的冲击诱导多裂过程进行了模拟，揭示了微观界面诱导的非平面激波效应引起的多裂损伤机理。纳米晶钛合金的微观界面对激波的传播产生非平面效应，对激波的传播产生阻碍。纳米晶双相钛合金中第二相晶粒的分布影响了非平面激波的形状。基于拉应力演化规律与多片孔洞成核原理的关系，首次发现在二次反射波与反射波相遇产生的拉应力作用下，多片孔洞在微观界面处成核。非均匀传播反射波相遇产生的拉应力的非均匀分布导致微观界面处多小孔隙的非均匀分布。第二相晶粒引起的位错密度增大阻碍了纳米晶双相钛合金的二次空洞形核，导致纳米晶单相钛合金与纳米晶双相钛合金的二次空洞形核存在差异。剥落阶段的损伤率（D˙）与冲击阶段的应变率（ε˙）呈正相关，并遵循如下关系：D˙=aε˙b （a和b为拟合参数，与材料的微观结构和冲击条件有关）。随着冲击速度的增加，纳米晶钛合金在微观界面处仍存在多孔洞形核，并出现晶间剥落。

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引用次数: 0

Excellent mechanical properties and superelasticity: bimodal heterostructure enhances NiTi alloy fabricated via laser powder bed fusion 优异的力学性能和超弹性：双峰异质结构增强了激光粉末床熔合制备的NiTi合金

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-05 DOI: 10.1016/j.ijplas.2025.104544

Minqian Liu , Danyang Lin , Yankun Zhang , Dong Wang , Bo Xiao , Lianyong Xu , Yongdian Han , Fumiyoshi Minami

Heterostructure (HS) materials are selected in natural evolution to exhibit superior mechanical and functional properties that traditional homogeneous materials cannot achieve. However, it is an open issue how to prepare HS alloys without destroying the advantages of laser powder bed fusion (LPBF) to directly form complex components. Here, based on the high stored energy of LPBF components, we obtained bimodal HS LPBF-NiTi shape memory alloys (SMAs) by recrystallization and abnormal grain growth induced by simple heat treatment after LPBF for the first time. The grain size of LPBF-NiTi SMAs can be regulated by modulating the heat treatment temperature. Homogeneous equiaxed fine grains (FGs), homogeneous coarse grains (CGs), and bimodal HS can be obtained after heat treatment at 780℃, 880℃, and 980℃, respectively. It is shown that LPBF-NiTi alloys with bimodal HS exhibit extraordinary strength-ductility (σ_MTS-δ balance: 13,810 MPa•%) and superelasticity (SE) (σ_C-δ_C balance: 2232 MPa•% and 96 % of SE recovery rate in 4 % applied strain). The intrinsic mechanism leading to property enhancement was studied through in-situ experiments and simulations. It is due to the strain optimization induced by heterogeneous regions, which promotes phase transformation and alleviates plastic deformation, avoiding strain localization. This work provides theoretical and practical significance for the property improvement and application promotion of the LPBF-NiTi alloy and may open a novel avenue for fabricating other LPBF alloys with HS.

异质结构（HS）材料是在自然进化过程中被选择出来的，具有传统均质材料无法达到的优越的力学和功能性能。然而，如何在不破坏激光粉末床熔合（LPBF）直接形成复杂部件的优点的情况下制备HS合金是一个悬而未决的问题。本文首次利用LPBF组分的高存储能量，通过LPBF后的再结晶和简单热处理引起的异常晶粒长大，获得了双峰HS LPBF- niti形状记忆合金（SMAs）。通过调节热处理温度可以调节LPBF-NiTi sma的晶粒尺寸。780℃、880℃和980℃热处理后，可获得均匀等轴细晶、均匀粗晶和双峰HS。结果表明，具有双峰HS的LPBF-NiTi合金表现出优异的强度-塑性（σMTS-δ平衡：13810 MPa•%）和超弹性（σC-δ c平衡：2232 MPa•%，在4%的应变下SE回收率为96%）。通过现场实验和模拟，研究了性能增强的内在机理。这是由于非均质区引起的应变优化，促进了相变，缓解了塑性变形，避免了应变局部化。本研究为LPBF- niti合金的性能改善和应用推广提供了理论和实际意义，并为利用HS制备其他LPBF合金开辟了新的途径。

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引用次数: 0

Scale-bridging dislocation plasticity in MgO at room temperature 室温下MgO的尺度桥接位错塑性

IF 12.8 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity

Pub Date : 2025-11-03 DOI: 10.1016/j.ijplas.2025.104533

Jiawen Zhang , Zhangtao Li , Yuwei Zhang , Hendrik Holz , James P. Best , Oliver Preuß , Zhenyong Chen , Yinan Cui , Xufei Fang , Wenjun Lu

Dislocations in ceramics have recently gained renewed research interest, in contrast to the traditional belief that ceramics are inherently brittle. Understanding dislocation mechanics in representative oxides is beneficial for effective dislocation engineering. Here, we use MgO single crystals with mechanically seeded dislocation densities from ∼10¹² to ∼10¹⁵ m^-2 to investigate the mechanical behavior such as yield and fracture. Micro-pillar compression tests reveal a dislocation density dependent yield strength, mediated by the varying dominating dislocation mechanisms from nucleation to multiplication/motion. In situ TEM compression measurements highlight the dislocation-seeded samples can achieve a much-improved compressive plastic strain beyond ∼70%, with a high yield strength of ∼2.35 GPa (diameter of ∼400 nm), indicating size effect. Complementary bulk compression tests, along with digital image correlation (DIC), demonstrate a consistent dislocation-mediated deformation and a notable size effect, with bulk samples exhibiting much reduced yield strength (∼120 MPa) compared to the nano-/micro-pillars. Using three-dimensional Discrete Dislocation Dynamics (3D-DDD) simulation, we further qualitatively analyze the collective dislocation activities (slip events) and work hardening during compression. This study provides new insights into dislocation-mediated plasticity in MgO, across different length scales, by systematically tuning dislocation density.

陶瓷中的位错最近获得了新的研究兴趣，与传统观念相反，陶瓷本质上是脆的。了解具有代表性的氧化物中的位错力学，有助于进行有效的位错工程。在这里，我们使用机械播种位错密度从~ 1012到~ 1015 m-2的MgO单晶来研究屈服和断裂等力学行为。微柱压缩试验揭示了位错密度依赖于屈服强度，由不同的主要位错机制介导，从成核到倍增/运动。原位TEM压缩测量显示，位错种子样品可以获得大大改善的压缩塑性应变，超过~ 70%，屈服强度高达~ 2.35 GPa（直径~ 400 nm），表明尺寸效应。互补体压缩测试，以及数字图像相关（DIC），证明了一致的位错介导的变形和显著的尺寸效应，与纳米/微柱相比，体样品的屈服强度大大降低（~ 120 MPa）。利用三维离散位错动力学（3D-DDD）模拟，我们进一步定性分析了压缩过程中的集体位错活动（滑移事件）和加工硬化。本研究通过系统调节位错密度，为MgO中位错介导的可塑性在不同长度尺度上提供了新的见解。

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引用次数: 0