Pub Date : 2024-11-08DOI: 10.1016/j.ijplas.2024.104163
C. Herath, K. Wijesinghe, J.G. Michopoulos, S.M. Arnold, A. Achuthan
In this study, the hierarchical deformation and anisotropic behavior of (α+β) Ti alloys are investigated using a novel microstructure-informed multiscale constitutive model. State-of-the-art crystal plasticity finite element (CPFE) models, due to their emphasis on a single length scale, are inadequate for capturing the complex hierarchical behavior of additively manufactured (AM) (α+β) titanium alloys, which are characterized by columnar grains and lamellar subgrain features at distinct length scales. To overcome this limitation, a decoupled multiscale framework was developed, integrating representative volume elements (RVEs) for both the columnar grain structure at the higher length scale and the subgrain microstructure at the lower length scale, with equal emphasis on each. The material behaviors at these scales were modeled using an anisotropic classical plasticity model and a mechanism-based CPFE model, respectively. The framework was experimentally validated for Directed Energy Deposition (DED) manufactured Ti-6Al-4V and used to investigate microscopic stress/strain fields, deformation localizations at grain and subgrain levels, and stress partitioning among neighboring grains. Insights from these studies led to the proposal of a new theory of anisotropy in AM (α+β) titanium alloys.
在本研究中，我们使用一种新型的微结构多尺度构成模型研究了（α+β）钛合金的分层变形和各向异性行为。最先进的晶体塑性有限元（CPFE）模型强调单一长度尺度，不足以捕捉添加制造（AM）（α+β）钛合金的复杂分层行为，这种合金在不同长度尺度上具有柱状晶粒和片状亚晶粒特征。为了克服这一局限性，我们开发了一个解耦多尺度框架，将较高长度尺度上的柱状晶粒结构和较低长度尺度上的亚晶粒微观结构的代表性体积元素（RVE）整合在一起，并对两者给予同等重视。这些尺度上的材料行为分别使用各向异性经典塑性模型和基于机理的 CPFE 模型进行建模。该框架在定向能沉积 (DED) 制造的 Ti-6Al-4V 中得到了实验验证，并用于研究微观应力/应变场、晶粒和亚晶粒级的变形定位以及相邻晶粒间的应力分配。通过这些研究，我们提出了 AM (α+β) 钛合金各向异性的新理论。
{"title":"Hierarchical Deformation and Anisotropic Behavior of (α+β) Ti Alloys: A Microstructure-Informed Multiscale Constitutive Model Study","authors":"C. Herath, K. Wijesinghe, J.G. Michopoulos, S.M. Arnold, A. Achuthan","doi":"10.1016/j.ijplas.2024.104163","DOIUrl":"https://doi.org/10.1016/j.ijplas.2024.104163","url":null,"abstract":"In this study, the hierarchical deformation and anisotropic behavior of (α+β) Ti alloys are investigated using a novel microstructure-informed multiscale constitutive model. State-of-the-art crystal plasticity finite element (CPFE) models, due to their emphasis on a single length scale, are inadequate for capturing the complex hierarchical behavior of additively manufactured (AM) (α+β) titanium alloys, which are characterized by columnar grains and lamellar subgrain features at distinct length scales. To overcome this limitation, a decoupled multiscale framework was developed, integrating representative volume elements (RVEs) for both the columnar grain structure at the higher length scale and the subgrain microstructure at the lower length scale, with equal emphasis on each. The material behaviors at these scales were modeled using an anisotropic classical plasticity model and a mechanism-based CPFE model, respectively. The framework was experimentally validated for Directed Energy Deposition (DED) manufactured Ti-6Al-4V and used to investigate microscopic stress/strain fields, deformation localizations at grain and subgrain levels, and stress partitioning among neighboring grains. Insights from these studies led to the proposal of a new theory of anisotropy in AM (α+β) titanium alloys.","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"1 1","pages":""},"PeriodicalIF":9.8,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The enhancement of strength and ductility of titanium matrix composites (TMCs) is crucial for lightweighting and expanding their advanced engineering applications. However, it is still a challenge for TMCs to achieve ultrahigh tensile strength with suitable ductility. In this study, a special low-temperature accumulative hot rolling (AHR) process was proposed to regulate the grain/phase boundaries and dislocation structures of TMCs reinforced with networked TiB. Through the AHR process, we have achieved exceptionally tensile strength and yield strength of 1570 MPa and 1460 MPa, respectively, accompanied with a suitable ductility of ∼7.5%. During the AHRed process, the majority of α-Ti grains rotated towards the favorable orientations, which display high SFs for basal slip in ND and prismatic slip in RD, respectively, resulting in the formation of {0002} texture. The accumulation and recovery of dislocations led to the formation of high-density sub-grain boundaries and geometrically necessary dislocations (GNDs) within α-Ti grains. Specifically, the GNDs rose dramatically from 1.06 × 1014 m−2 to 8.16 × 1014 m−2, whereas the size of α-Ti grains decreased significantly from 6.8 to 1.1 μm. In the β phase grains, secondary phase transformation was induced via the AHR process, resulting in the introduction of high-density nano-scaled secondary α-Ti lamellae (∼4 nm) with a fully coherent interface {110}BCC//{0002}HCP. After the AHR process, the crack nucleation and prolongation along the networked TiB was inhibited, resulting in the enhancement of ductility. This special AHR strategy, combining grain/hetero-phase boundary engineering and dislocation engineering, has great potential and universality for designing TMCs with both ultrahigh strength and suitable ductility.
{"title":"Achieving high strength and ductility of titanium matrix composite reinforced with networked TiB via SPS sintering of core-shell powder and accumulative hot rolling","authors":"Guo-Dong Sun, Jun-Jie Cheng, Ze-Kun Zheng, Jing-Li Zhang, Xu-Wen Su, Peng-Fei Zhang, Ming-Jia Li, Jun-Jie Xu, Xiao-Qi Mao, Long-Long Dong, Ming-Yang Li","doi":"10.1016/j.ijplas.2024.104166","DOIUrl":"https://doi.org/10.1016/j.ijplas.2024.104166","url":null,"abstract":"The enhancement of strength and ductility of titanium matrix composites (TMCs) is crucial for lightweighting and expanding their advanced engineering applications. However, it is still a challenge for TMCs to achieve ultrahigh tensile strength with suitable ductility. In this study, a special low-temperature accumulative hot rolling (AHR) process was proposed to regulate the grain/phase boundaries and dislocation structures of TMCs reinforced with networked TiB. Through the AHR process, we have achieved exceptionally tensile strength and yield strength of 1570 MPa and 1460 MPa, respectively, accompanied with a suitable ductility of ∼7.5%. During the AHRed process, the majority of α-Ti grains rotated towards the favorable orientations, which display high SFs for basal slip in ND and prismatic slip in RD, respectively, resulting in the formation of {0002} texture. The accumulation and recovery of dislocations led to the formation of high-density sub-grain boundaries and geometrically necessary dislocations (GNDs) within α-Ti grains. Specifically, the GNDs rose dramatically from 1.06 × 10<sup>14</sup> m<sup>−2</sup> to 8.16 × 10<sup>14</sup> m<sup>−2</sup>, whereas the size of α-Ti grains decreased significantly from 6.8 to 1.1 μm. In the β phase grains, secondary phase transformation was induced via the AHR process, resulting in the introduction of high-density nano-scaled secondary α-Ti lamellae (∼4 nm) with a fully coherent interface {110}<sub>BCC</sub>//{0002}<sub>HCP</sub>. After the AHR process, the crack nucleation and prolongation along the networked TiB was inhibited, resulting in the enhancement of ductility. This special AHR strategy, combining grain/hetero-phase boundary engineering and dislocation engineering, has great potential and universality for designing TMCs with both ultrahigh strength and suitable ductility.","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"1 1","pages":""},"PeriodicalIF":9.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.ijplas.2024.104168
Kwanghyun Yu , Jeong Whan Yoon
This study proposes the compressive fracture characterization method using bilinear strain paths: pre-tension and compression. Compressive ductile fracture exhibits extremely large strain, which has been regarded as being difficult to be measured. Large deformation under compressive loading makes the shape of a specimen barreled and changes the stress triaxiality rapidly. Due to these complicated and large strains, compressive fracture strain can be considered to be within the so-called cut-off region where no fracture occurs. In order to enable compression tests to be easier, an approach that can lower the range of fracture strain is needed. Uniaxial tensile deformation is a strain path that induces the growth of voids inside ductile materials and leads to ductility reduction. Ductile materials subjected to pre-tensile loading before compressive loading can show the premature compressive fracture. A ductile fracture model capable of predicting the cut-off region is selected for ductile fracture loci of the bilinear strain paths and implemented into the numerical simulation with different pre-tensile strain levels. The verification of the proposed characterization method is performed by comparing experimental data and simulation results for fractured specimen shapes and load-displacement curves.
{"title":"Characterization of compressive fracture strain based on bilinear strain paths","authors":"Kwanghyun Yu , Jeong Whan Yoon","doi":"10.1016/j.ijplas.2024.104168","DOIUrl":"10.1016/j.ijplas.2024.104168","url":null,"abstract":"<div><div>This study proposes the compressive fracture characterization method using bilinear strain paths: pre-tension and compression. Compressive ductile fracture exhibits extremely large strain, which has been regarded as being difficult to be measured. Large deformation under compressive loading makes the shape of a specimen barreled and changes the stress triaxiality rapidly. Due to these complicated and large strains, compressive fracture strain can be considered to be within the so-called cut-off region where no fracture occurs. In order to enable compression tests to be easier, an approach that can lower the range of fracture strain is needed. Uniaxial tensile deformation is a strain path that induces the growth of voids inside ductile materials and leads to ductility reduction. Ductile materials subjected to pre-tensile loading before compressive loading can show the premature compressive fracture. A ductile fracture model capable of predicting the cut-off region is selected for ductile fracture loci of the bilinear strain paths and implemented into the numerical simulation with different pre-tensile strain levels. The verification of the proposed characterization method is performed by comparing experimental data and simulation results for fractured specimen shapes and load-displacement curves.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104168"},"PeriodicalIF":9.4,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142594299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.ijplas.2024.104164
Gustavo Bertoli , Amy J. Clarke , Michael J. Kaufman , Claudio S. Kiminami , Francisco G. Coury
A Cr40Co40Ni20 (at.%) alloy with different grain/crystallite sizes was analyzed through in-situ synchrotron X-ray diffraction during tensile testing. The FCC starting structure underwent a partial strain-induced transformation to HCP (TRIP effect) and the percent transformed was measured throughout the deformation. The critical stress required to form a certain HCP fraction was shown to follow a Hall-Petch relation (σTRIP = σTRIP,0+ kTRIPd-0.5), with the Hall-Petch slope being approximately the same for yield stress and TRIP effect (ky ≈ kTRIP). Furthermore, this work developed a Hall-Petch-based model that correlates the applied stress, the transformed phase fraction, and the initial FCC grain/crystallite size. It predicts the stress required to form a certain HCP fraction, or the fraction formed when a certain stress is applied, for different grain/crystallite sizes. We also proposed a mechanism to explain the grain/crystallite size dependence of the TRIP effect and discuss how the TRIP effect and its early activation in the Cr40Co40Ni20 alloy provide high work-hardening capacity, which improves ductility and toughness. Here, a refined FCC grain size (d = 1.3; c = 0.7 μm) was shown to increase the yield stress by at least 100 % (417 → 834 MPa), compared to a coarser grain material (17; 6.8 μm), while maintaining a high ductility of 41 %. This work contributes to a better understanding of the deformation mechanisms, mainly the strain-induced phase transformation (TRIP), highlighting their impact and importance on mechanical properties.
{"title":"Influence of grain size on strain-induced phase transformation in a CrCoNi multi-principal element alloy","authors":"Gustavo Bertoli , Amy J. Clarke , Michael J. Kaufman , Claudio S. Kiminami , Francisco G. Coury","doi":"10.1016/j.ijplas.2024.104164","DOIUrl":"10.1016/j.ijplas.2024.104164","url":null,"abstract":"<div><div>A Cr<sub>40</sub>Co<sub>40</sub>Ni<sub>20</sub> (at.%) alloy with different grain/crystallite sizes was analyzed through <em>in-situ</em> synchrotron X-ray diffraction during tensile testing. The FCC starting structure underwent a partial strain-induced transformation to HCP (TRIP effect) and the percent transformed was measured throughout the deformation. The critical stress required to form a certain HCP fraction was shown to follow a Hall-Petch relation (<em>σ<sub>TRIP</sub> = σ<sub>TRIP,</sub></em><sub>0</sub> <em>+ k<sub>TRIP</sub>d<sup>-0.5</sup></em>), with the Hall-Petch slope being approximately the same for yield stress and TRIP effect (<em>k<sub>y</sub></em> ≈ <em>k<sub>TRIP</sub></em>). Furthermore, this work developed a Hall-Petch-based model that correlates the applied stress, the transformed phase fraction, and the initial FCC grain/crystallite size. It predicts the stress required to form a certain HCP fraction, or the fraction formed when a certain stress is applied, for different grain/crystallite sizes. We also proposed a mechanism to explain the grain/crystallite size dependence of the TRIP effect and discuss how the TRIP effect and its early activation in the Cr<sub>40</sub>Co<sub>40</sub>Ni<sub>20</sub> alloy provide high work-hardening capacity, which improves ductility and toughness. Here, a refined FCC grain size (<em>d</em> = 1.3; <em>c</em> = 0.7 μm) was shown to increase the yield stress by at least 100 % (417 → 834 MPa), compared to a coarser grain material (17; 6.8 μm), while maintaining a high ductility of 41 %. This work contributes to a better understanding of the deformation mechanisms, mainly the strain-induced phase transformation (TRIP), highlighting their impact and importance on mechanical properties.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104164"},"PeriodicalIF":9.4,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-05DOI: 10.1016/j.ijplas.2024.104160
Liuyong He , Jiang Zheng , Mengning Xu , Tianjiao Li , Dongdi Yin , Bin Jiang , Fusheng Pan , Hao Zhou
Navigating the strength-ductility trade-off has been a persistent challenge in Mg alloys. Here, we address this issue through a novel multiple-direction pre-deformation at room temperature that introduces a high density of 〈c + a〉 dislocations into pure Mg via dislocation transmutation. This approach achieves a remarkable enhancement in the strength-ductility synergy, increasing the yield strength from 87.6 MPa to 156.6 MPa and improving elongation to failure from 7.7% to 17.6%. In general, introducing a high-density 〈c + a〉 dislocations in Mg alloys have been difficult due to the high CRSS at room temperature. Our findings reveal that extension twinning can act as a “dislocation converter,” transforming basal 〈a〉 dislocations in the matrix into 〈c + a〉 dislocations within twins. Intensive basal 〈a〉 dislocations were induced in pure Mg through pre-tension and subsequently transformed into 〈c + a〉 dislocations via extension twinning during compression. This process led to a substantial number of 〈c + a〉 dislocations and I1 stacking faults, contributing to the enhanced strength. The high density of 〈c + a〉 dislocations, combined with I1 stacking faults and a reduced c/a ratio within twins, enhances the activity of pyramidal 〈c + a〉 slip, thereby significantly improving ductility. This dislocation transmutation strategy offers a promising way for producing strength-ductility synergy in Mg alloys.
{"title":"Towards extraordinary strength-ductility synergy in pure Mg via dislocation transmutation","authors":"Liuyong He , Jiang Zheng , Mengning Xu , Tianjiao Li , Dongdi Yin , Bin Jiang , Fusheng Pan , Hao Zhou","doi":"10.1016/j.ijplas.2024.104160","DOIUrl":"10.1016/j.ijplas.2024.104160","url":null,"abstract":"<div><div>Navigating the strength-ductility trade-off has been a persistent challenge in Mg alloys. Here, we address this issue through a novel multiple-direction pre-deformation at room temperature that introduces a high density of 〈<em>c</em> + <em>a</em>〉 dislocations into pure Mg via dislocation transmutation. This approach achieves a remarkable enhancement in the strength-ductility synergy, increasing the yield strength from 87.6 MPa to 156.6 MPa and improving elongation to failure from 7.7% to 17.6%. In general, introducing a high-density 〈<em>c</em> + <em>a</em>〉 dislocations in Mg alloys have been difficult due to the high CRSS at room temperature. Our findings reveal that extension twinning can act as a “dislocation converter,” transforming basal 〈a〉 dislocations in the matrix into 〈<em>c</em> + <em>a</em>〉 dislocations within twins. Intensive basal 〈a〉 dislocations were induced in pure Mg through pre-tension and subsequently transformed into 〈<em>c</em> + <em>a</em>〉 dislocations via extension twinning during compression. This process led to a substantial number of 〈<em>c</em> + <em>a</em>〉 dislocations and I<sub>1</sub> stacking faults, contributing to the enhanced strength. The high density of 〈<em>c</em> + <em>a</em>〉 dislocations, combined with I<sub>1</sub> stacking faults and a reduced c/a ratio within twins, enhances the activity of pyramidal 〈<em>c</em> + <em>a</em>〉 slip, thereby significantly improving ductility. This dislocation transmutation strategy offers a promising way for producing strength-ductility synergy in Mg alloys.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104160"},"PeriodicalIF":9.4,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142580559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-04DOI: 10.1016/j.ijplas.2024.104161
Jinhua Zhou , Jing Wang , Jungang Ren , Robert O. Ritchie , Zuncheng Wang , Yuchao Wu , Zhufeng He , Xin Wang , Ying Fu , Yifu Jiang , Lin Wang , Xiaowei Yin
The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.
{"title":"Exceptional tensile ductility and strength of a BCC structure CLAM steel with lamellar grains at 77 kelvin","authors":"Jinhua Zhou , Jing Wang , Jungang Ren , Robert O. Ritchie , Zuncheng Wang , Yuchao Wu , Zhufeng He , Xin Wang , Ying Fu , Yifu Jiang , Lin Wang , Xiaowei Yin","doi":"10.1016/j.ijplas.2024.104161","DOIUrl":"10.1016/j.ijplas.2024.104161","url":null,"abstract":"<div><div>The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104161"},"PeriodicalIF":9.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-04DOI: 10.1016/j.ijplas.2024.104162
Shilei Liu , Haitao Gao , Daixiu Wei , Charlie Kong , L.S.R. Kumara , M.W. Fu , Hailiang Yu
Face-centered cubic (FCC) medium entropy alloys (MEAs) have received considerable attention due to their impressive mechanical properties and responses. However, their practical application is limited by their modest yield strengths. The potential enhancement of the mechanical properties of single-phase MEAs was explored in this study through a synergistic approach combining heterogeneous structure design with subsequent cryo-pre-straining. A heterogeneous lamella structure was produced in a single-phase Fe55Mn20Cr15Ni10 MEA via two-step rolling and annealing. Cryo-pre-straining at varying degrees (6, 12, 21, and 36%) introduced hexagonal close-packed (HCP) phase, high-density dislocations, twins, and stacking faults, leveraging the reduced stacking fault energy at cryogenic temperatures. This process enhanced the alloy's yield strength from 353 MPa to 1.2 GPa (compared to the baseline uniform coarse-grained structure), while maintaining an acceptable total elongation of 8.4%. The impact of cryo-pre-straining on the microstructure and mechanical properties of the MEA was assessed using in-situ synchrotron X-ray diffraction analysis. Cryo-pre-straining (36%) achieved a higher dislocation density (6.1 × 1015m−2) compared to room-temperature straining (2.5 × 1015m−2). The stress contribution from HCP-martensite and the evolution of dislocation density during loading were quantified, along with observations of negative stacking fault probability and strain-induced HCP→FCC reverse transformation in cryo-pre-strained samples under loading conditions. Furthermore, the contributions of regulated microstructures to the enhancement of yield strength were quantitatively assessed.
面心立方（FCC）中熵合金（MEAs）因其令人印象深刻的机械性能和反应而备受关注。然而，它们的实际应用却因屈服强度不高而受到限制。本研究通过异质结构设计与后续低温预拉伸相结合的协同方法，探索了提高单相中熵合金机械性能的潜力。通过两步轧制和退火，在单相 Fe55Mn20Cr15Ni10 MEA 中产生了异质薄片结构。不同程度的低温预应变（6%、12%、21% 和 36%）引入了六方紧密堆积（HCP）相、高密度位错、孪晶和堆积断层，充分利用了低温下堆积断层能量的降低。这一过程将合金的屈服强度从 353 兆帕提高到 1.2 GPa（与基线均匀粗晶粒结构相比），同时保持了 8.4% 的可接受总伸长率。利用原位同步辐射 X 射线衍射分析评估了低温预拉伸对 MEA 的微观结构和机械性能的影响。与室温应变（2.5 × 1015 m-2）相比，低温预应变（36%）实现了更高的位错密度（6.1 × 1015 m-2）。在加载条件下，对低温预应变样品的负堆积断层概率和应变诱导的 HCP→FCC 反向转变进行了观察，同时量化了加载过程中 HCP-马氏体的应力贡献和位错密度的演变。此外，还定量评估了规范微结构对提高屈服强度的贡献。
{"title":"Deformation mechanism of a metastable medium entropy alloy strengthened by the synergy of heterostructure design and cryo-pre-straining","authors":"Shilei Liu , Haitao Gao , Daixiu Wei , Charlie Kong , L.S.R. Kumara , M.W. Fu , Hailiang Yu","doi":"10.1016/j.ijplas.2024.104162","DOIUrl":"10.1016/j.ijplas.2024.104162","url":null,"abstract":"<div><div>Face-centered cubic (FCC) medium entropy alloys (MEAs) have received considerable attention due to their impressive mechanical properties and responses. However, their practical application is limited by their modest yield strengths. The potential enhancement of the mechanical properties of single-phase MEAs was explored in this study through a synergistic approach combining heterogeneous structure design with subsequent cryo-pre-straining. A heterogeneous lamella structure was produced in a single-phase Fe<sub>55</sub>Mn<sub>20</sub>Cr<sub>15</sub>Ni<sub>10</sub> MEA via two-step rolling and annealing. Cryo-pre-straining at varying degrees (6, 12, 21, and 36%) introduced hexagonal close-packed (HCP) phase, high-density dislocations, twins, and stacking faults, leveraging the reduced stacking fault energy at cryogenic temperatures. This process enhanced the alloy's yield strength from 353 MPa to 1.2 GPa (compared to the baseline uniform coarse-grained structure), while maintaining an acceptable total elongation of 8.4%. The impact of cryo-pre-straining on the microstructure and mechanical properties of the MEA was assessed using <em>in</em>-<em>situ</em> synchrotron X-ray diffraction analysis. Cryo-pre-straining (36%) achieved a higher dislocation density (6.1 × 10<sup>15</sup> <em>m</em><sup>−2</sup>) compared to room-temperature straining (2.5 × 10<sup>15</sup> <em>m</em><sup>−2</sup>). The stress contribution from HCP-martensite and the evolution of dislocation density during loading were quantified, along with observations of negative stacking fault probability and strain-induced HCP→FCC reverse transformation in cryo-pre-strained samples under loading conditions. Furthermore, the contributions of regulated microstructures to the enhancement of yield strength were quantitatively assessed.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104162"},"PeriodicalIF":9.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we perform a comprehensive study of the dynamic deformation and fracture of brass, including Taylor tests with classical and profiled cylinders and ball throwing experiments reaching the strain rates of about (0.1−1)/μs, as well as atomistic and continuum-level numerical modeling. Molecular dynamics (MD) simulations are used to construct the equation of state (EOS) of brass and to study its fracture characteristics at shear deformation under negative pressure. An original model of fracture under combined tensile-shear loading is formulated, which takes into account both the accumulation of empty volume in the process of lattice loosening due to the lattice defect production in the course of plastic deformation and further mechanical growth of voids controlled by the dislocation plasticity. This atomic-scale model is transmitted to the macroscopic experiment-scale level and embedded into 3D dislocation plasticity model to describe the dynamic deformation and fracture of brass using the numerical scheme of smoothed particle hydrodynamics (SPH). A part of experimental data is used to find the optimal parameters of the dislocation plasticity model by means of the Bayesian global optimization method accelerated with the help of artificial-neural-network (ANN)-based emulator of the 3D model. Another part of experimental data is used to fit the fracture model parameter. The remaining experimental data, which are not used in the parameterization, are applied to verify the parameterized model. The developed physical-based model provides correct and meaningful description of the dynamic deformation and fracture of brass, while the developed formalized approach to its parameterization opens a way to wider use of this type of models in the engineering applications, including studies on dynamic performance and high-speed processing technologies.
{"title":"Dynamic deformation and fracture of brass: Experiments and dislocation-based model","authors":"E.S. Rodionov, V.V. Pogorelko, V.G. Lupanov, A.G. Fazlitdinova, P.N. Mayer, A.E. Mayer","doi":"10.1016/j.ijplas.2024.104165","DOIUrl":"10.1016/j.ijplas.2024.104165","url":null,"abstract":"<div><div>In this work, we perform a comprehensive study of the dynamic deformation and fracture of brass, including Taylor tests with classical and profiled cylinders and ball throwing experiments reaching the strain rates of about (0.1−1)/μs, as well as atomistic and continuum-level numerical modeling. Molecular dynamics (MD) simulations are used to construct the equation of state (EOS) of brass and to study its fracture characteristics at shear deformation under negative pressure. An original model of fracture under combined tensile-shear loading is formulated, which takes into account both the accumulation of empty volume in the process of lattice loosening due to the lattice defect production in the course of plastic deformation and further mechanical growth of voids controlled by the dislocation plasticity. This atomic-scale model is transmitted to the macroscopic experiment-scale level and embedded into 3D dislocation plasticity model to describe the dynamic deformation and fracture of brass using the numerical scheme of smoothed particle hydrodynamics (SPH). A part of experimental data is used to find the optimal parameters of the dislocation plasticity model by means of the Bayesian global optimization method accelerated with the help of artificial-neural-network (ANN)-based emulator of the 3D model. Another part of experimental data is used to fit the fracture model parameter. The remaining experimental data, which are not used in the parameterization, are applied to verify the parameterized model. The developed physical-based model provides correct and meaningful description of the dynamic deformation and fracture of brass, while the developed formalized approach to its parameterization opens a way to wider use of this type of models in the engineering applications, including studies on dynamic performance and high-speed processing technologies.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104165"},"PeriodicalIF":9.4,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-31DOI: 10.1016/j.ijplas.2024.104157
Pan-Dong Lin, Jun-Feng Nie, Wen-Dong Cui, Lei He, Shu-Gang Cui, Guo-Chao Gu, Gui-Yong Xiao, Yu-Peng Lu
The stacking fault tetrahedron (SFT) formation displays a pronounced size effect, progressing from vacancy equilateral triangular plate to perfect SFT, and eventually to truncated SFT, as demonstrated in numerous irradiated face-centered cubic metals. However, the presence of distinct SFT structures in F321 stainless steel has not been reported. This study explored the SFT formation mechanism in irradiated F321 stainless steel using transmission electron microscopy (TEM), molecular dynamics (MD) simulations, and machine learning. SFTs, Frank loops, and Lomer-Cottrell locks were found to be widely generated in the irradiated F321 steel. The critical size for truncated and perfect SFTs was determined using MD simulations; the results were consistent with the theoretical predictions. Additionally, the twin boundaries observed through TEM, which were attributed to the elevated tensile stress near the boundaries, facilitated the formation of perfect SFTs. Moreover, interstitial Frank loops also facilitated the formation of perfect SFTs. This study also explored the influence of variations in Ni and Cr concentrations on the critical size n1 for the transition from vacancy plates to perfect SFTs and n2 for the transition from perfect SFTs to truncated SFTs, using a combination of MD and machine learning methods. As the Ni concentration increased and the Cr concentration decreased, n1 and n2 increased; conversely, the critical sizes decreased when the Ni concentration decreased and the Cr concentration increased. These insights reveal the systematic mechanism of SFT formation under varied conditions, offering new perspectives for understanding the nano-defects in F321 stainless steel.
{"title":"Understanding Stacking Fault Tetrahedron Formation in FCC Stainless Steel: A Fusion of Transmission Electron Microscopy, Molecular Dynamics, and Machine Learning","authors":"Pan-Dong Lin, Jun-Feng Nie, Wen-Dong Cui, Lei He, Shu-Gang Cui, Guo-Chao Gu, Gui-Yong Xiao, Yu-Peng Lu","doi":"10.1016/j.ijplas.2024.104157","DOIUrl":"https://doi.org/10.1016/j.ijplas.2024.104157","url":null,"abstract":"The stacking fault tetrahedron (SFT) formation displays a pronounced size effect, progressing from vacancy equilateral triangular plate to perfect SFT, and eventually to truncated SFT, as demonstrated in numerous irradiated face-centered cubic metals. However, the presence of distinct SFT structures in F321 stainless steel has not been reported. This study explored the SFT formation mechanism in irradiated F321 stainless steel using transmission electron microscopy (TEM), molecular dynamics (MD) simulations, and machine learning. SFTs, Frank loops, and Lomer-Cottrell locks were found to be widely generated in the irradiated F321 steel. The critical size for truncated and perfect SFTs was determined using MD simulations; the results were consistent with the theoretical predictions. Additionally, the twin boundaries observed through TEM, which were attributed to the elevated tensile stress near the boundaries, facilitated the formation of perfect SFTs. Moreover, interstitial Frank loops also facilitated the formation of perfect SFTs. This study also explored the influence of variations in Ni and Cr concentrations on the critical size <em>n<sub>1</sub></em> for the transition from vacancy plates to perfect SFTs and <em>n<sub>2</sub></em> for the transition from perfect SFTs to truncated SFTs, using a combination of MD and machine learning methods. As the Ni concentration increased and the Cr concentration decreased, <em>n<sub>1</sub></em> and <em>n<sub>2</sub></em> increased; conversely, the critical sizes decreased when the Ni concentration decreased and the Cr concentration increased. These insights reveal the systematic mechanism of SFT formation under varied conditions, offering new perspectives for understanding the nano-defects in F321 stainless steel.","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"41 1","pages":""},"PeriodicalIF":9.8,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142542092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.ijplas.2024.104153
Amirhossein Lame Jouybari , Samir El Shawish , Leon Cizelj
The Strain Gradient Crystal Plasticity (SGCP) model, based on cumulative shear strain, is developed to regularize and simulate the size effect behavior of polycrystalline aggregates, specifically addressing the formation of localization bands, such as slip and kink bands, influenced by strain softening during the initial stages of plastic deformation. In this respect, the thermodynamically consistent derivation of the SGCP equations is presented, establishing their connection to the kinematics of classical crystal plasticity (CCP) framework. The governing balance equations are solved using the fixed-point algorithm of the fast Fourier transform (FFT)-homogenization method, involving explicit coupling between the classical and SGCP balance equations. To address this problem, a strong 21-voxel finite difference scheme is established. This scheme is considered to solve the higher order balance equation inherent to SGCP. Additionally, three types of interface conditions are implemented to explore the impact of grain boundaries on the transmission of localization bands. These conditions yield consistent intragranular/transgranular localization patterns in the MicroFree and MicroContinuity cases, while in the MicroHard condition all localization bands are intragranular with stress concentrations appearing at the grain boundaries.
Analytical solutions corresponding to different material behaviors are developed and compared with numerical results to validate the numerical implementation of the FFT fixed-point algorithm. It is observed that both the macroscopic behavior and microscopic variables in CCP framework are highly influenced by grid resolutions (non-objective), leading to numerical instabilities arising from the material softening and subsequent formation of localization bands, both in single crystals and polycrystalline aggregates. Remarkably, the developed SGCP model provides results that are independent of grid resolutions (objective) and effectively regularizes the material behavior on local scale. Moreover, the non-local parameter of the model is capable of controlling the localization band widths. Finally, the proposed SGCP model, together with employed MicroHard condition on grain boundaries, is demonstrated to qualitatively reproduce main microstructural features of irradiated polycrystalline materials.
{"title":"Fast Fourier transform approach to Strain Gradient Crystal Plasticity: Regularization of strain localization and size effect","authors":"Amirhossein Lame Jouybari , Samir El Shawish , Leon Cizelj","doi":"10.1016/j.ijplas.2024.104153","DOIUrl":"10.1016/j.ijplas.2024.104153","url":null,"abstract":"<div><div>The Strain Gradient Crystal Plasticity (SGCP) model, based on cumulative shear strain, is developed to regularize and simulate the size effect behavior of polycrystalline aggregates, specifically addressing the formation of localization bands, such as slip and kink bands, influenced by strain softening during the initial stages of plastic deformation. In this respect, the thermodynamically consistent derivation of the SGCP equations is presented, establishing their connection to the kinematics of classical crystal plasticity (CCP) framework. The governing balance equations are solved using the fixed-point algorithm of the fast Fourier transform (FFT)-homogenization method, involving explicit coupling between the classical and SGCP balance equations. To address this problem, a strong 21-voxel finite difference scheme is established. This scheme is considered to solve the higher order balance equation inherent to SGCP. Additionally, three types of interface conditions are implemented to explore the impact of grain boundaries on the transmission of localization bands. These conditions yield consistent intragranular/transgranular localization patterns in the MicroFree and MicroContinuity cases, while in the MicroHard condition all localization bands are intragranular with stress concentrations appearing at the grain boundaries.</div><div>Analytical solutions corresponding to different material behaviors are developed and compared with numerical results to validate the numerical implementation of the FFT fixed-point algorithm. It is observed that both the macroscopic behavior and microscopic variables in CCP framework are highly influenced by grid resolutions (non-objective), leading to numerical instabilities arising from the material softening and subsequent formation of localization bands, both in single crystals and polycrystalline aggregates. Remarkably, the developed SGCP model provides results that are independent of grid resolutions (objective) and effectively regularizes the material behavior on local scale. Moreover, the non-local parameter of the model is capable of controlling the localization band widths. Finally, the proposed SGCP model, together with employed MicroHard condition on grain boundaries, is demonstrated to qualitatively reproduce main microstructural features of irradiated polycrystalline materials.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"183 ","pages":"Article 104153"},"PeriodicalIF":9.4,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142541511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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