Pub Date : 2024-11-04DOI: 10.1016/j.actamat.2024.120526
Changxi Liu , Lai-Chang Zhang , Kuaishe Wang , Liqiang Wang
Refractory high entropy alloys (RHEAs), as a novel class of multi-principal element alloys, have attracted significant attention owing to their excellent properties. However, their low plasticity limits their potential applications, while the high melting points of the alloying elements face challenges to additive manufacturing (AM). Herein, RHEA, with extensively distributed cellular structure within their grains, was successfully fabricated using AM. Furthermore, we proposed a simple strategy to form a complete dislocation network within the cellular structure region in advance through cyclic deformation processing in the elastic stage (microplastic deformation). Dislocation networks are entangled with other dislocations, creating numerous pinned points adjacent cell walls, which impede dislocation motion. As a result, the cyclic deformation processing of RHEA achieves a yield strength of 1136 MPa while maintaining 50 % deformation strain without fracturing. The cyclic deformation processing method provides a route to strengthen additively manufactured alloys, offering a solution to overcome the trade-off between strength and plasticity.
难熔高熵合金（RHEAs）作为一类新型多主元素合金，因其优异的性能而备受关注。然而，它们的低塑性限制了其潜在的应用领域，而合金元素的高熔点又给增材制造（AM）带来了挑战。在此，我们利用 AM 成功制造出了晶粒内具有广泛分布的蜂窝结构的 RHEA。此外，我们还提出了一种简单的策略，即通过弹性阶段的循环变形处理（微塑性变形），提前在蜂窝结构区域内形成完整的位错网络。位错网络与其他位错纠缠在一起，在邻近细胞壁的地方形成了许多钉点，从而阻碍了位错运动。因此，RHEA 的循环变形加工可达到 1136 兆帕的屈服强度，同时保持 50%的变形应变而不发生断裂。循环变形加工方法为强化添加剂制造的合金提供了一条途径，为克服强度和塑性之间的权衡提供了一种解决方案。
{"title":"Improving strength and plasticity via pre-assembled dislocation networks in additively manufactured refractory high entropy alloy","authors":"Changxi Liu , Lai-Chang Zhang , Kuaishe Wang , Liqiang Wang","doi":"10.1016/j.actamat.2024.120526","DOIUrl":"10.1016/j.actamat.2024.120526","url":null,"abstract":"<div><div>Refractory high entropy alloys (RHEAs), as a novel class of multi-principal element alloys, have attracted significant attention owing to their excellent properties. However, their low plasticity limits their potential applications, while the high melting points of the alloying elements face challenges to additive manufacturing (AM). Herein, RHEA, with extensively distributed cellular structure within their grains, was successfully fabricated using AM. Furthermore, we proposed a simple strategy to form a complete dislocation network within the cellular structure region in advance through cyclic deformation processing in the elastic stage (microplastic deformation). Dislocation networks are entangled with other dislocations, creating numerous pinned points adjacent cell walls, which impede dislocation motion. As a result, the cyclic deformation processing of RHEA achieves a yield strength of 1136 MPa while maintaining 50 % deformation strain without fracturing. The cyclic deformation processing method provides a route to strengthen additively manufactured alloys, offering a solution to overcome the trade-off between strength and plasticity.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120526"},"PeriodicalIF":8.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574654","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.actamat.2024.120528
Eliana M. Feygin , Christopher A. Schuh
Significant effort has been put into designing shape-memory materials that can survive many cycles without functional or structural fatigue. A component of the design process is the condition defining perfect interface compatibility between the austenite and martensite lattices (λ2 = 1). In this paper, we evaluate the traditional mathematical theories of martensite under applied stresses, which distort the lattice compatibility through elastic strains. In NiTi we find that elastic distortions resulting from applied stresses influence the interface compatibility to a degree of impacting the material's functional abilities. Combining our results with empirical relationships connecting interface compatibility to transformation hysteresis we show that the model matches reasonably to a number of experimental results in the literature in which hysteresis changes under applied loads. We also apply these theories to a shape-memory ceramic (zirconia), which suggests a large orientation-dependence and asymmetric behavior in tension and compression. In both systems, we find that variant selection plays a large role in whether interface compatibility will improve or worsen under stress.
{"title":"Interface compatibility and hysteresis in shape memory materials are affected by lattice distortions from applied stresses","authors":"Eliana M. Feygin , Christopher A. Schuh","doi":"10.1016/j.actamat.2024.120528","DOIUrl":"10.1016/j.actamat.2024.120528","url":null,"abstract":"<div><div>Significant effort has been put into designing shape-memory materials that can survive many cycles without functional or structural fatigue. A component of the design process is the condition defining perfect interface compatibility between the austenite and martensite lattices (λ<sub>2</sub> = 1). In this paper, we evaluate the traditional mathematical theories of martensite under applied stresses, which distort the lattice compatibility through elastic strains. In NiTi we find that elastic distortions resulting from applied stresses influence the interface compatibility to a degree of impacting the material's functional abilities. Combining our results with empirical relationships connecting interface compatibility to transformation hysteresis we show that the model matches reasonably to a number of experimental results in the literature in which hysteresis changes under applied loads. We also apply these theories to a shape-memory ceramic (zirconia), which suggests a large orientation-dependence and asymmetric behavior in tension and compression. In both systems, we find that variant selection plays a large role in whether interface compatibility will improve or worsen under stress.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120528"},"PeriodicalIF":8.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574656","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, molecular dynamics (MD) simulations of ferroelectric BaTiO are used to generate parameters for a phase-field (PF) model. The MD simulations provide important input parameters, such as elastic and piezoelectric properties, as well as domain wall (DW) widths and velocities. A parameterization technique is proposed to incorporate the MD results into the PF simulations, allowing for the generation of relevant parameters. Anisotropic interface energy coefficients are used to match the widths of both the 180° and 90° DWs in the PF simulations to the MD data. The velocities of the DWs are calculated and compared to the results obtained from MD simulations, demonstrating excellent agreement. Furthermore, we investigate the disparity between coercive fields obtained from PF simulations and MD simulations. Initially, our PF simulations yield coercive fields approximately twice as high as those observed in MD simulations. To address this discrepancy, we introduce a nucleus into the PF simulation system. The parameters of this nucleus are derived from a statistical analysis of coercive field data from MD simulations. By incorporating the nucleus model, we achieve a coercive field in PF simulations that closely aligns with the MD results. Validation of the parameterized PF model using MD data obtained with different initial conditions and thermodynamic constraints shows good agreement, further confirming the model’s accuracy.
{"title":"Parameterization of a phase field model for ferroelectrics from molecular dynamics data","authors":"Dilshod Durdiev , Frank Wendler , Michael Zaiser , Hikaru Azuma , Takahiro Tsuzuki , Shuji Ogata , Tomohiro Ogawa , Ryo Kobayashi , Masayuki Uranagase","doi":"10.1016/j.actamat.2024.120513","DOIUrl":"10.1016/j.actamat.2024.120513","url":null,"abstract":"<div><div>In this work, molecular dynamics (MD) simulations of ferroelectric BaTiO<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> are used to generate parameters for a phase-field (PF) model. The MD simulations provide important input parameters, such as elastic and piezoelectric properties, as well as domain wall (DW) widths and velocities. A parameterization technique is proposed to incorporate the MD results into the PF simulations, allowing for the generation of relevant parameters. Anisotropic interface energy coefficients are used to match the widths of both the 180° and 90° DWs in the PF simulations to the MD data. The velocities of the DWs are calculated and compared to the results obtained from MD simulations, demonstrating excellent agreement. Furthermore, we investigate the disparity between coercive fields obtained from PF simulations and MD simulations. Initially, our PF simulations yield coercive fields approximately twice as high as those observed in MD simulations. To address this discrepancy, we introduce a nucleus into the PF simulation system. The parameters of this nucleus are derived from a statistical analysis of coercive field data from MD simulations. By incorporating the nucleus model, we achieve a coercive field in PF simulations that closely aligns with the MD results. Validation of the parameterized PF model using MD data obtained with different initial conditions and thermodynamic constraints shows good agreement, further confirming the model’s accuracy.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120513"},"PeriodicalIF":8.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579898","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}
Pub Date : 2024-11-04DOI: 10.1016/j.actamat.2024.120533
Yu Qian , Wenjia Wang , Yu Wang , Andong Xiao , Yao Liu , Ge Zhang , Zhizhi Xu , Yun Pan , Guanqi Wang , Xiaobing Ren , Yuanchao Ji
Superelastic alloys, being successfully used in cutting-edge space technologies, are desired to possess large recoverable strain and wide working temperature range simultaneously. However, achieving such a combination has proven challenging. Here we report a finding of crossover strain glass transition in the crossover region between martensite and strain glass regimes of temperature vs. annealing-time phase diagram of cold-rolled Ti50Ni50 alloys. The crossover strain glass alloy exhibits a large recoverable strain of ∼ 4%-6% and ultrawide working temperature range from 453 to 93 K, outperforming previously reported superelastic alloys. Moreover, such exceptional properties were revealed to stem from the crossover strain glass transition occurring at a high transition temperature Tg ∼ 276 K, which possesses a unique transition behavior of strain glass transition accompanied by a sluggish and partial martensitic transformation from strain glass to martensite with cooling. This transition was further characterized by in-situ microscopic observations: upon cooling both several nanometer-sized and dozens of nanometer-sized B19’ martensitic domains gradually appear and increase in the matrix of B2 parent phase over a wide temperature range, which contribute to large recoverable strain and ultrawide working temperature range. Our work indicates that the crossover strain glass may provide a new mechanism to achieve large recoverable strain over a wide temperature range, and large field-induced strain over a wide temperature range may be obtained in other crossover ferroic glasses.
超弹性合金已成功应用于尖端空间技术，人们希望它能同时拥有较大的可恢复应变和较宽的工作温度范围。然而，事实证明实现这样的组合具有挑战性。在此，我们报告了在冷轧 Ti50Ni50 合金的温度与退火时间相图的马氏体和应变玻璃之间的交叉区域发现的交叉应变玻璃转变。这种交叉应变玻璃化合金表现出 4%-6% 的大可恢复应变和 453 至 93 K 的超宽工作温度范围，优于之前报道的超弹性合金。此外，研究还揭示了这种特殊性能源于在高转变温度 Tg ∼ 276 K 时发生的交叉应变玻璃转变，这种转变具有独特的应变玻璃转变行为，伴随着冷却时从应变玻璃到马氏体的缓慢和部分马氏体转变。通过原位显微观察进一步确定了这一转变的特征：冷却时，B2 母相的基体中会逐渐出现几个纳米级和几十个纳米级的 B19' 马氏体畴，并在较宽的温度范围内逐渐增大，从而产生较大的可恢复应变和超宽的工作温度范围。我们的研究表明，交叉应变玻璃可能为在宽温度范围内实现大可回收应变提供了一种新机制，而在其他交叉铁玻璃中也可能获得宽温度范围内的大场致应变。
{"title":"Crossover strain glass alloy exhibiting large recoverable strain over a wide temperature range","authors":"Yu Qian , Wenjia Wang , Yu Wang , Andong Xiao , Yao Liu , Ge Zhang , Zhizhi Xu , Yun Pan , Guanqi Wang , Xiaobing Ren , Yuanchao Ji","doi":"10.1016/j.actamat.2024.120533","DOIUrl":"10.1016/j.actamat.2024.120533","url":null,"abstract":"<div><div>Superelastic alloys, being successfully used in cutting-edge space technologies, are desired to possess large recoverable strain and wide working temperature range simultaneously. However, achieving such a combination has proven challenging. Here we report a finding of crossover strain glass transition in the crossover region between martensite and strain glass regimes of temperature vs. annealing-time phase diagram of cold-rolled Ti<sub>50</sub>Ni<sub>50</sub> alloys. The crossover strain glass alloy exhibits a large recoverable strain of ∼ 4%-6% and ultrawide working temperature range from 453 to 93 K, outperforming previously reported superelastic alloys. Moreover, such exceptional properties were revealed to stem from the crossover strain glass transition occurring at a high transition temperature <em>T</em><sub>g</sub> ∼ 276 K, which possesses a unique transition behavior of strain glass transition accompanied by a sluggish and partial martensitic transformation from strain glass to martensite with cooling. This transition was further characterized by <em>in-situ</em> microscopic observations: upon cooling both several nanometer-sized and dozens of nanometer-sized B19’ martensitic domains gradually appear and increase in the matrix of B2 parent phase over a wide temperature range, which contribute to large recoverable strain and ultrawide working temperature range. Our work indicates that the crossover strain glass may provide a new mechanism to achieve large recoverable strain over a wide temperature range, and large field-induced strain over a wide temperature range may be obtained in other crossover ferroic glasses.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120533"},"PeriodicalIF":8.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574655","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.actamat.2024.120538
Cameran Beg, Jaemin Byeon, Nova Berman, John Kieffer
We explore the concept of correlative activation free energy (CAFE) for the analysis and interpretation of viscosity data of a collection of 847 inorganic oxide glass formers that exhibit various degrees of non-Arrhenius behavior. The CAFE model formalism is strictly based on transition state theory and accounts for the variation in the activation barrier height for the viscous dissipation due to the structural evolution the system undergoes upon traversing the glass transition regime. Thus, fitting parameters are meaningful in a statistical thermodynamic context. Compared to the VFT and MYEGA equations, fits using the CAFE model are more robust when extrapolating to infinite temperature because the latter encodes non-enthalpic contributions to the rate coefficient more realistically. The CAFE model-based analysis reveals a strong connection between melt fragility and the degree of change in the potential energy landscape with temperature. Accordingly, while the average ground-state potential energy of the glass forming liquid gradually increases with temperature, the energy of the activated state remains relatively invariant. Our analysis also allows one to estimate the number of atoms involved in the viscous relaxation process, which ranges from approximately 10 to 50 atoms for the oxide glass formers studied. We observe that thermally activated dynamic phenomena exhibited by glassy networks, such as the mixed alkali effect, persist into the supercooled liquid state.
{"title":"Correlative activation free energy (CAFE) model: Application to viscous processes in inorganic oxide glass-formers","authors":"Cameran Beg, Jaemin Byeon, Nova Berman, John Kieffer","doi":"10.1016/j.actamat.2024.120538","DOIUrl":"10.1016/j.actamat.2024.120538","url":null,"abstract":"<div><div>We explore the concept of correlative activation free energy (CAFE) for the analysis and interpretation of viscosity data of a collection of 847 inorganic oxide glass formers that exhibit various degrees of non-Arrhenius behavior. The CAFE model formalism is strictly based on transition state theory and accounts for the variation in the activation barrier height for the viscous dissipation due to the structural evolution the system undergoes upon traversing the glass transition regime. Thus, fitting parameters are meaningful in a statistical thermodynamic context. Compared to the VFT and MYEGA equations, fits using the CAFE model are more robust when extrapolating to infinite temperature because the latter encodes non-enthalpic contributions to the rate coefficient more realistically. The CAFE model-based analysis reveals a strong connection between melt fragility and the degree of change in the potential energy landscape with temperature. Accordingly, while the average ground-state potential energy of the glass forming liquid gradually increases with temperature, the energy of the activated state remains relatively invariant. Our analysis also allows one to estimate the number of atoms involved in the viscous relaxation process, which ranges from approximately 10 to 50 atoms for the oxide glass formers studied. We observe that thermally activated dynamic phenomena exhibited by glassy networks, such as the mixed alkali effect, persist into the supercooled liquid state.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120538"},"PeriodicalIF":8.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142580053","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 : 2024-11-02DOI: 10.1016/j.actamat.2024.120527
Seok-Hyun Hong , Hyung-Jun Cho , Selim Kim , Sang Yoon Song , Hyun Chung , Suk-kyu Lee , Sunghak Lee , Seok Su Sohn , Sung-Joon Kim
This study addresses critical issues of hydrogen embrittlement (HE) and liquid metal embrittlement (LME) in Al-Si-coated and Zn-coated hot-press-forming (HPF) steel sheets, respectively, by proposing an innovative approach of incorporating (24–30) wt% Zn into the conventional Al-Si (AS) coating to mitigate HE issues while leveraging the absence of LME associated with Zn coating. To the best of the authors' knowledge, no other paper has considered this subject. The optimal Al-Si-Zn (ASZ) sheet formed a surface oxide layer and Zn-enriched zone, acting as local trap sites to reduce H intrusion, while the AS sheet lacked this zone, leading to continuous H intrusion. The ASZ sheet reached complete H emission in 4 weeks, whereas significant H remained in the AS sheet even after 4 weeks due to higher H intrusion. This result emphasizes the crucial role of Zn addition in impeding H diffusion and ensuring excellent resistance to HE. Bending angles at peak load, crucial for assessing bending and sheet forming properties, were adversely affected by diffusible H contents within the sheets. When austenitized at 900 °C for 3 min and then cooled to 800 °C for tensile testing, the ASZ sheet experienced abrupt premature fracture due to selective Zn diffusion from the liquid alloy to grain boundaries, inducing LME. However, prolonged austenitization to 6 min mitigated LME, with no expected issues on LME. These findings underscore the significance of the tailored Al-Si-Zn coating in enhancing resistance to HE, making it suitable for broad applications in high-strength HPF steel sheets.
本研究针对铝硅涂层和锌涂层热压成形（HPF）钢板中分别存在的氢脆（HE）和液态金属脆化（LME）的关键问题，提出了一种创新方法，即在传统的铝硅（AS）涂层中加入 (24-30) wt% 的锌，以减轻氢脆问题，同时利用锌涂层不存在 LME 的特性。据作者所知，还没有其他论文考虑过这一问题。最佳的铝硅锌（ASZ）薄片形成了一个表面氧化层和富含锌的区域，作为局部捕集点，减少了氢的侵入，而 AS 薄片则缺少这一区域，导致氢的持续侵入。ASZ 薄膜在 4 周后达到完全的 H 排放，而 AS 薄膜由于 H 入侵较多，即使在 4 周后仍有大量 H 残留。这一结果强调了添加锌在阻碍 H 扩散和确保优异的抗 HE 性能方面的关键作用。峰值载荷下的弯曲角对评估弯曲和板材成型性能至关重要，而板材中的可扩散 H 含量对弯曲角产生了不利影响。当在900°C下奥氏体化3分钟，然后冷却到800°C进行拉伸测试时，ASZ板材会因选择性锌从液态合金扩散到晶界而突然过早断裂，导致LME。不过，将奥氏体化时间延长至 6 分钟可减轻 LME，预计不会出现 LME 问题。这些发现强调了定制 Al-Si-Zn 涂层在增强抗高炉效应方面的重要作用，使其适用于高强度 HPF 钢板的广泛应用。
{"title":"Enhancing resistance to hydrogen embrittlement in high-strength hot-press-forming steel sheets through Al-Si-Zn coating optimization","authors":"Seok-Hyun Hong , Hyung-Jun Cho , Selim Kim , Sang Yoon Song , Hyun Chung , Suk-kyu Lee , Sunghak Lee , Seok Su Sohn , Sung-Joon Kim","doi":"10.1016/j.actamat.2024.120527","DOIUrl":"10.1016/j.actamat.2024.120527","url":null,"abstract":"<div><div>This study addresses critical issues of hydrogen embrittlement (HE) and liquid metal embrittlement (LME) in Al-Si-coated and Zn-coated hot-press-forming (HPF) steel sheets, respectively, by proposing an innovative approach of incorporating (24–30) wt% Zn into the conventional Al-Si (AS) coating to mitigate HE issues while leveraging the absence of LME associated with Zn coating. To the best of the authors' knowledge, no other paper has considered this subject. The optimal Al-Si-Zn (ASZ) sheet formed a surface oxide layer and Zn-enriched zone, acting as local trap sites to reduce H intrusion, while the AS sheet lacked this zone, leading to continuous H intrusion. The ASZ sheet reached complete H emission in 4 weeks, whereas significant H remained in the AS sheet even after 4 weeks due to higher H intrusion. This result emphasizes the crucial role of Zn addition in impeding H diffusion and ensuring excellent resistance to HE. Bending angles at peak load, crucial for assessing bending and sheet forming properties, were adversely affected by diffusible H contents within the sheets. When austenitized at 900 °C for 3 min and then cooled to 800 °C for tensile testing, the ASZ sheet experienced abrupt premature fracture due to selective Zn diffusion from the liquid alloy to grain boundaries, inducing LME. However, prolonged austenitization to 6 min mitigated LME, with no expected issues on LME. These findings underscore the significance of the tailored Al-Si-Zn coating in enhancing resistance to HE, making it suitable for broad applications in high-strength HPF steel sheets.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120527"},"PeriodicalIF":8.3,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563074","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 : 2024-11-02DOI: 10.1016/j.actamat.2024.120508
Fei Shuang , Luca Laurenti , Poulumi Dey
In this study, we explore the mechanisms underlying the exceptional intrinsic strength of face-centered cubic (FCC) Multi-Principal Element Alloys (MPEAs) using a multifaceted approach. Our methods integrate atomistic simulations, informed by both embedded-atom model and neural network potentials, with first-principles calculations, stochastic Peierls-Nabarro (PN) modeling, and symbolic machine learning. We identify a consistent, robust linear correlation between the strength of MPEAs and the standard deviation of the maximum stacking-fault restoring force (τmax,sd) across various potentials. This finding is substantiated by comparing the experimental strengths of Cantor alloys’ subsystems and Ni62.5V37.5 against τmax,sd values from high-throughput first-principle calculations. Our theoretical insights are derived from integrating the stochastic Peierls-Nabarro model with a shearable precipitation hardening framework, demonstrating that lattice distortion alone does not directly enhance intrinsic strength. Instead, τmax,sd emerges as a critical determinant, capable of boosting the strength of MPEAs by up to tenfold. Our analysis reveals the critical role of the exponential form of the PN model in achieving substantial strength improvement by transforming the Gaussian-like distribution of τmax into an exponential-like distribution of local Peierls stress. Additionally, using an advanced symbolic machine learning technique, the sure independence screening and sparsifying operator (SISSO) method, we derive interpretable relationships between MPEA strength, elastic properties, and τmax statistics, offering new insights into the design and optimization of advanced MPEAs. These findings highlight that the nonlinear physics and atomic fluctuations characterizing MPEAs not only underpin their unconventional intrinsic strength but also contribute to other complex properties such as sluggish diffusion and cocktail effect.
{"title":"Standard deviation in maximum restoring force controls the intrinsic strength of face-centered cubic multi-principal element alloys","authors":"Fei Shuang , Luca Laurenti , Poulumi Dey","doi":"10.1016/j.actamat.2024.120508","DOIUrl":"10.1016/j.actamat.2024.120508","url":null,"abstract":"<div><div>In this study, we explore the mechanisms underlying the exceptional intrinsic strength of face-centered cubic (FCC) Multi-Principal Element Alloys (MPEAs) using a multifaceted approach. Our methods integrate atomistic simulations, informed by both embedded-atom model and neural network potentials, with first-principles calculations, stochastic Peierls-Nabarro (PN) modeling, and symbolic machine learning. We identify a consistent, robust linear correlation between the strength of MPEAs and the standard deviation of the maximum stacking-fault restoring force (<em>τ</em><sub>max,sd</sub>) across various potentials. This finding is substantiated by comparing the experimental strengths of Cantor alloys’ subsystems and Ni<sub>62.5</sub>V<sub>37.5</sub> against <em>τ</em><sub>max,sd</sub> values from high-throughput first-principle calculations. Our theoretical insights are derived from integrating the stochastic Peierls-Nabarro model with a shearable precipitation hardening framework, demonstrating that lattice distortion alone does not directly enhance intrinsic strength. Instead, <em>τ</em><sub>max,sd</sub> emerges as a critical determinant, capable of boosting the strength of MPEAs by up to tenfold. Our analysis reveals the critical role of the exponential form of the PN model in achieving substantial strength improvement by transforming the Gaussian-like distribution of <em>τ</em><sub>max</sub> into an exponential-like distribution of local Peierls stress. Additionally, using an advanced symbolic machine learning technique, the sure independence screening and sparsifying operator (SISSO) method, we derive interpretable relationships between MPEA strength, elastic properties, and <em>τ</em><sub>max</sub> statistics, offering new insights into the design and optimization of advanced MPEAs. These findings highlight that the nonlinear physics and atomic fluctuations characterizing MPEAs not only underpin their unconventional intrinsic strength but also contribute to other complex properties such as sluggish diffusion and cocktail effect.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120508"},"PeriodicalIF":8.3,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142566092","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}
Pub Date : 2024-11-02DOI: 10.1016/j.actamat.2024.120497
I. Escobar-Moreno, E. Nieto-Valeiras, J. LLorca
Slip transfer/blocking at grain and twin boundaries as well as preferential fatigue crack nucleation locations were studied in two solution-hardened Ni-based alloys (Inconel 600 and Hastelloy C276) deformed under strain-controlled, fully-reversed cyclic deformation in the low-cycle fatigue regime. Electron backscatter diffraction-based slip trace analysis was used to identify the active slip systems after interrupted fatigue tests. It was found that the Luster-Morris parameter was an accurate geometrical criteria to discriminate between slip transfer and blocking at grain and twin boundaries. Moreover, it was found that fatigue cracks initiation was always intergranular and cracks were nucleated at grain and twin boundaries when the slip transfer across was blocked. The probability of crack nucleation increased with the misorientation angle and was independent of the grain size. This behavior was associated with the development of stress concentrations at grain and twin boundaries as well as triple junctions in which slip was blocked and is different from previous reports on fatigue crack nucleation in Ni-based superalloys deformed, in which the slip system parallel to the TB in the parent grain was suitably oriented for slip. This contrast in the fatigue crack nucleation sites between both types of Ni alloys were attributed to the differences in the degree of strain localization and show how this factor controls damage nucleation in polycrystals.
{"title":"Slip transfer and crack initiation at grain and twin boundaries during strain-controlled fatigue of solution-hardened Ni-based alloys","authors":"I. Escobar-Moreno, E. Nieto-Valeiras, J. LLorca","doi":"10.1016/j.actamat.2024.120497","DOIUrl":"10.1016/j.actamat.2024.120497","url":null,"abstract":"<div><div>Slip transfer/blocking at grain and twin boundaries as well as preferential fatigue crack nucleation locations were studied in two solution-hardened Ni-based alloys (Inconel 600 and Hastelloy C276) deformed under strain-controlled, fully-reversed cyclic deformation in the low-cycle fatigue regime. Electron backscatter diffraction-based slip trace analysis was used to identify the active slip systems after interrupted fatigue tests. It was found that the Luster-Morris parameter <span><math><mrow><msup><mrow><mi>m</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>=</mo><mn>0</mn><mo>.</mo><mn>6</mn></mrow></math></span> was an accurate geometrical criteria to discriminate between slip transfer and blocking at grain and twin boundaries. Moreover, it was found that fatigue cracks initiation was always intergranular and cracks were nucleated at grain and twin boundaries when the slip transfer across was blocked. The probability of crack nucleation increased with the misorientation angle and was independent of the grain size. This behavior was associated with the development of stress concentrations at grain and twin boundaries as well as triple junctions in which slip was blocked and is different from previous reports on fatigue crack nucleation in Ni-based superalloys deformed, in which the slip system parallel to the TB in the parent grain was suitably oriented for slip. This contrast in the fatigue crack nucleation sites between both types of Ni alloys were attributed to the differences in the degree of strain localization and show how this factor controls damage nucleation in polycrystals.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120497"},"PeriodicalIF":8.3,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142566131","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.actamat.2024.120504
Xiang Li , Yixiao Jiang , Qianqian Jin , Fei Qin , Tingting Yao , Ang Tao , Xuexi Yan , Chunyang Gao , Zhiqing Yang , Chunlin Chen , Gang Liu , Xiu-Liang Ma , Hengqiang Ye
Elemental doping at coherent interfaces is very difficult and rarely used to improve the interfacial properties since coherent interfaces have low interfacial energies and lack open space for trapping dopant atoms. Exploring universally applicable strategies for elemental doping at coherent interfaces represents an important progress in interface science and engineering. In this study, Nb atoms are successfully doped at coherent (001) LaAlO3/anatase-TiO2 interfaces, which enhances greatly the efficiency of photocatalytic hydrogen production from water. Transmission electron microscopy investigations reveal that both LaO- terminated and AlO2-terminated LaAlO3/anatase-TiO2 interfaces can trap two layers of Nb atoms, which accompanies with the formation of La vacancies between them. First-principles calculations suggest that Nb atoms segregate at the interfaces under the action of potential gradient, which increases significantly the strength of the built-in electric field in TiO2, thereby facilitating the separation of photogenerated carriers and improving the photocatalytic performance. The H2 production of the Nb doped coherent interface is about 4 times that of the pristine coherent interface. Since potential gradient widely exists at various interfaces including the coherent ones, elemental doping by potential gradient should be an universally applicable fabrication method for tuning the properties of interfaces and heterostructures.
{"title":"Nb-doped coherent TiO2/LaAlO3 interfaces: Segregation mechanism and improved photocatalytic performance","authors":"Xiang Li , Yixiao Jiang , Qianqian Jin , Fei Qin , Tingting Yao , Ang Tao , Xuexi Yan , Chunyang Gao , Zhiqing Yang , Chunlin Chen , Gang Liu , Xiu-Liang Ma , Hengqiang Ye","doi":"10.1016/j.actamat.2024.120504","DOIUrl":"10.1016/j.actamat.2024.120504","url":null,"abstract":"<div><div>Elemental doping at coherent interfaces is very difficult and rarely used to improve the interfacial properties since coherent interfaces have low interfacial energies and lack open space for trapping dopant atoms. Exploring universally applicable strategies for elemental doping at coherent interfaces represents an important progress in interface science and engineering. In this study, Nb atoms are successfully doped at coherent (001) LaAlO<sub>3</sub>/anatase-TiO<sub>2</sub> interfaces, which enhances greatly the efficiency of photocatalytic hydrogen production from water. Transmission electron microscopy investigations reveal that both LaO- terminated and AlO<sub>2</sub>-terminated LaAlO<sub>3</sub>/anatase-TiO<sub>2</sub> interfaces can trap two layers of Nb atoms, which accompanies with the formation of La vacancies between them. First-principles calculations suggest that Nb atoms segregate at the interfaces under the action of potential gradient, which increases significantly the strength of the built-in electric field in TiO<sub>2</sub>, thereby facilitating the separation of photogenerated carriers and improving the photocatalytic performance. The H<sub>2</sub> production of the Nb doped coherent interface is about 4 times that of the pristine coherent interface. Since potential gradient widely exists at various interfaces including the coherent ones, elemental doping by potential gradient should be an universally applicable fabrication method for tuning the properties of interfaces and heterostructures.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120504"},"PeriodicalIF":8.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142556405","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.actamat.2024.120521
Christopher Hutchinson, Yves Brechet
Nucleation is the first step of the phase transformations that we use to control the microstructures of engineering materials. The starting point for questions of nucleation is usually Classical Nucleation Theory (CNT) but for solid-state nucleation at low temperatures where atomic mobility is limited, such as in engineering alloys, CNT has not been very successful is quantitatively predicting nucleation. A strong assumption of CNT is that all thermally-induced stochastic fluctuations, no matter how far their compositions lie from the bulk alloy composition, are possible and that they become nuclei when a critical size determined from thermodynamics is reached.
Here we present a new and complementary model for solid-state nucleation. We consider the other extreme where atomic mobility is limited and thermally-induced stochastic clusters cannot form in the time scale relevant for a nucleation event. Instead, we consider the geometric clusters that are a statistical feature of any solution as the origin of the nuclei and present a simple model for the number of nuclei and their rate of ‘activation’. This new ‘geometric cluster’ model is shown to be able to successfully predict the competition in phase nucleation during the crystallization of a series of Al-Ni-Y metallic glass, predict the solvent trapping that is increasingly seen in solid-state nucleation and predict the peak number density of precipitates observed in Cu-Co and Fe-Cu alloys.
{"title":"A new approach to solid-state nucleation in kinetically-constrained systems","authors":"Christopher Hutchinson, Yves Brechet","doi":"10.1016/j.actamat.2024.120521","DOIUrl":"10.1016/j.actamat.2024.120521","url":null,"abstract":"<div><div>Nucleation is the first step of the phase transformations that we use to control the microstructures of engineering materials. The starting point for questions of nucleation is usually Classical Nucleation Theory (CNT) but for solid-state nucleation at low temperatures where atomic mobility is limited, such as in engineering alloys, CNT has not been very successful is quantitatively predicting nucleation. A strong assumption of CNT is that all thermally-induced stochastic fluctuations, no matter how far their compositions lie from the bulk alloy composition, are possible and that they become nuclei when a critical size determined from thermodynamics is reached.</div><div>Here we present a new and complementary model for solid-state nucleation. We consider the other extreme where atomic mobility is limited and thermally-induced stochastic clusters cannot form in the time scale relevant for a nucleation event. Instead, we consider the geometric clusters that are a statistical feature of any solution as the origin of the nuclei and present a simple model for the number of nuclei and their rate of ‘activation’. This new ‘geometric cluster’ model is shown to be able to successfully predict the competition in phase nucleation during the crystallization of a series of Al-Ni-Y metallic glass, predict the solvent trapping that is increasingly seen in solid-state nucleation and predict the peak number density of precipitates observed in Cu-Co and Fe-Cu alloys.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120521"},"PeriodicalIF":8.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142556409","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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