For the application of nanoindentation on the nanoscale, the dislocation behavior affected by solid solution strengthening can be described microscopically, which contributes to comprehend the peculiarity of high-entropy alloys (HEAs). This study is to provide deeper insights into the dislocation motion within the plastic zone and reveal the material dependence of the plastic zone variation in multi-principal alloys through designed nanoindentation linear tests performed on face-centered cubic Ni, CoNi, CoCrNi, and FeCoCrNi metals and alloys. Indentation tests at various depths further confirmed that the scale factor, f , which was proposed to modify the Nix-Gao model, is governed by the material category. From this, a connection is established between f and pertinent parameters of dislocation activation process and distribution characteristics. As for the dislocation activation, the activation volume and theoretical strength are considered, and then the lattice distortion and strain gradient determine the dislocation distribution feature. Regarding the critical strengthening of adjacent indentations, a critical scale factor f eff of the strengthening boundary is defined, which is proportional to the indentation depth, and a large f eff is preferred for high-strength multi-principal HEAs and /or medium-entropy alloys (MEAs). Combining the f and the f eff of the four metals and alloys, a model describing the evolution of the indentation plastic zone is established, in which the plastic zone include three parts. For the inconsonant trends of f and f eff , a dislocation saturation zone is suggested to existing in the plastic zone. The Gradient plastic zone model proposed here graphically depicts the dislocations motion, as well as its reinforcement effect. Futhermore, this model lends credence to modify the framework which describes the mechanical response of materials under nanoindentation.
{"title":"Gradient Plastic Zone Model in Equiatomic Face-Centered Cubic Alloys","authors":"Q. Zhang, X. Jin, H. J. Yang, X. H. Shi, J. Qiao","doi":"10.2139/ssrn.3922863","DOIUrl":"https://doi.org/10.2139/ssrn.3922863","url":null,"abstract":"For the application of nanoindentation on the nanoscale, the dislocation behavior affected by solid solution strengthening can be described microscopically, which contributes to comprehend the peculiarity of high-entropy alloys (HEAs). This study is to provide deeper insights into the dislocation motion within the plastic zone and reveal the material dependence of the plastic zone variation in multi-principal alloys through designed nanoindentation linear tests performed on face-centered cubic Ni, CoNi, CoCrNi, and FeCoCrNi metals and alloys. Indentation tests at various depths further confirmed that the scale factor, f , which was proposed to modify the Nix-Gao model, is governed by the material category. From this, a connection is established between f and pertinent parameters of dislocation activation process and distribution characteristics. As for the dislocation activation, the activation volume and theoretical strength are considered, and then the lattice distortion and strain gradient determine the dislocation distribution feature. Regarding the critical strengthening of adjacent indentations, a critical scale factor f eff of the strengthening boundary is defined, which is proportional to the indentation depth, and a large f eff is preferred for high-strength multi-principal HEAs and /or medium-entropy alloys (MEAs). Combining the f and the f eff of the four metals and alloys, a model describing the evolution of the indentation plastic zone is established, in which the plastic zone include three parts. For the inconsonant trends of f and f eff , a dislocation saturation zone is suggested to existing in the plastic zone. The Gradient plastic zone model proposed here graphically depicts the dislocations motion, as well as its reinforcement effect. Futhermore, this model lends credence to modify the framework which describes the mechanical response of materials under nanoindentation.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81693035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The additive manufacturability of nickel-based superalloys for laser powder bed fusion (LPBF) technologies is studied by considering the in-process cracking mechanisms. The additive manufacturability of nickel-based superalloys largely depends on the resistance to the liquid and solid-state cracking. Herein, we propose a two-parameter-based, heat resistance and deformation resistance (HR-DR) model, accounting for the relation between chemical composition (both major and minor elements) and cracking susceptibility, which is generalized from the elemental microsegregation behavior and mechanisms of LPBF process induced cracking. The proposed model is validated by the LPBF experiments in this study and by the hitherto reported data in LPBF superalloys community. The HR-DR-model is found to be a theoretically acceptable and easy-to-use approach for the prediction of in-process cracking of nickel-based superalloys during LPBF. The influence of alloying elements and the γ′ precipitates on the additive manufacturability is discussed. The model provides a path for designing not only new solid solutioning, but also and more importantly γ′ strengthened nickel-based superalloys for LPBF applications.
研究了镍基高温合金在激光粉末床熔合(LPBF)工艺中的可增材制造性。镍基高温合金的增材制造性能在很大程度上取决于其抗液态和固态开裂的能力。本文从LPBF工艺诱发裂纹的元素微偏析行为和机理出发，提出了一种考虑化学成分(主要元素和次要元素)与裂纹敏感性之间关系的基于双参数的耐热和变形抗力(HR-DR)模型。该模型通过本研究的LPBF实验和LPBF高温合金界迄今报道的数据进行了验证。hr - dr -模型是一种理论上可接受且易于使用的预测镍基高温合金LPBF过程中裂纹的方法。讨论了合金元素和γ′析出物对增材可加工性的影响。该模型不仅为设计新的固溶体，更重要的是为设计用于LPBF的γ′强化镍基高温合金提供了途径。
{"title":"Modelling of Additive Manufacturability of Nickel-Based Superalloys for Laser Powder Bed Fusion","authors":"Jinghao Xu, P. Kontis, R. Peng, J. Moverare","doi":"10.2139/ssrn.3910606","DOIUrl":"https://doi.org/10.2139/ssrn.3910606","url":null,"abstract":"The additive manufacturability of nickel-based superalloys for laser powder bed fusion (LPBF) technologies is studied by considering the in-process cracking mechanisms. The additive manufacturability of nickel-based superalloys largely depends on the resistance to the liquid and solid-state cracking. Herein, we propose a two-parameter-based, heat resistance and deformation resistance (HR-DR) model, accounting for the relation between chemical composition (both major and minor elements) and cracking susceptibility, which is generalized from the elemental microsegregation behavior and mechanisms of LPBF process induced cracking. The proposed model is validated by the LPBF experiments in this study and by the hitherto reported data in LPBF superalloys community. The HR-DR-model is found to be a theoretically acceptable and easy-to-use approach for the prediction of in-process cracking of nickel-based superalloys during LPBF. The influence of alloying elements and the γ′ precipitates on the additive manufacturability is discussed. The model provides a path for designing not only new solid solutioning, but also and more importantly γ′ strengthened nickel-based superalloys for LPBF applications.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"53 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91402704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuxuan Chen, A. Li, Xiangguang Kong, Zhiyuan Ma, Genfa Kang, D. Jiang, Kun Zhao, Y. Ren, L. Cui, Kaiyuan Yu
The challenges in the identification of reversible twinning modes and in the measurement of reversible twinning strain impede the thorough understanding of twinning induced elasticity (TIE). In this report, we exploited the mode and strain of reversible twinning in B19' martensite in a Nb-nanowire/NiTiFe-matrix alloy. TIE strain up to 5.1% was achieved by pre-deforming the alloy up to an applied strain of 55.7%. In situ synchrotron X-ray diffraction (XRD) results show that B19' ( ) and ( ) twins were induced by pre-deformation. More importantly, a large portion of these twins were found reversible for the first time. It is suggested that the reversibility is likely due to the pinning effects of high density dislocations and nanosized martensite variants or twins. Furthermore, the reversible twinning strain was measured using XRD based on a 'lattice strain matching' concept such that the contribution of reversible twinning to TIE was clarified. The measured twinning strain was compared with the calculated strain based on twinning crystallography.
{"title":"Revealing the Mode and Strain of Reversible Twinning in B19' Martensite by in situ Synchrotron X-Ray Diffraction","authors":"Yuxuan Chen, A. Li, Xiangguang Kong, Zhiyuan Ma, Genfa Kang, D. Jiang, Kun Zhao, Y. Ren, L. Cui, Kaiyuan Yu","doi":"10.2139/ssrn.3927817","DOIUrl":"https://doi.org/10.2139/ssrn.3927817","url":null,"abstract":"The challenges in the identification of reversible twinning modes and in the measurement of reversible twinning strain impede the thorough understanding of twinning induced elasticity (TIE). In this report, we exploited the mode and strain of reversible twinning in B19' martensite in a Nb-nanowire/NiTiFe-matrix alloy. TIE strain up to 5.1% was achieved by pre-deforming the alloy up to an applied strain of 55.7%. In situ synchrotron X-ray diffraction (XRD) results show that B19' ( ) and ( ) twins were induced by pre-deformation. More importantly, a large portion of these twins were found reversible for the first time. It is suggested that the reversibility is likely due to the pinning effects of high density dislocations and nanosized martensite variants or twins. Furthermore, the reversible twinning strain was measured using XRD based on a 'lattice strain matching' concept such that the contribution of reversible twinning to TIE was clarified. The measured twinning strain was compared with the calculated strain based on twinning crystallography.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86297309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ability to efficiently generate microstructure instances corresponding to specified two-point statistics is a crucial capability in rigorously studying random heterogeneous materials within the Integrated Computational Materials Engineering and Materials Informatics frameworks. However, the lack of computationally efficient, statistically expressive models for achieving this transformation is a recurring roadblock in many foundational Materials Informatics challenges. In this article, we present a theoretical and computational framework for generating stationary, periodic microstructural instances corresponding to specified stationary, periodic two-point statistics by stochastically modeling the microstructure as an N-output Gaussian Random Field. First, we illustrate how two-point statistics can be used to parameterize anisotropic Gaussian Random Fields. Second, we derive analytic relationships between the two-point statistics and the spatially resolved sampled microstructures, within the approximation of a N-output Gaussian Random Field. Finally, we propose the algorithms necessary to efficiently sample these fields in O (S ln S) computational complexity and while incurring O (S) memory cost. We also discuss the current limitations of the proposed framework, and its usefulness to future Materials Informatics workflows.
{"title":"Efficient Generation of Anisotropic N-Field Microstructures From 2-Point Statistics Using Multi-Output Gaussian Random Fields","authors":"A. E. Robertson, S. Kalidindi","doi":"10.2139/ssrn.3949516","DOIUrl":"https://doi.org/10.2139/ssrn.3949516","url":null,"abstract":"The ability to efficiently generate microstructure instances corresponding to specified two-point statistics is a crucial capability in rigorously studying random heterogeneous materials within the Integrated Computational Materials Engineering and Materials Informatics frameworks. However, the lack of computationally efficient, statistically expressive models for achieving this transformation is a recurring roadblock in many foundational Materials Informatics challenges. In this article, we present a theoretical and computational framework for generating stationary, periodic microstructural instances corresponding to specified stationary, periodic two-point statistics by stochastically modeling the microstructure as an N-output Gaussian Random Field. First, we illustrate how two-point statistics can be used to parameterize anisotropic Gaussian Random Fields. Second, we derive analytic relationships between the two-point statistics and the spatially resolved sampled microstructures, within the approximation of a N-output Gaussian Random Field. Finally, we propose the algorithms necessary to efficiently sample these fields in O (S ln S) computational complexity and while incurring O (S) memory cost. We also discuss the current limitations of the proposed framework, and its usefulness to future Materials Informatics workflows.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"100 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77567570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report the first application of in-situ liquid cell transmission electron microscopy (LC-TEM) to research hydration reactions of nano OPC, providing nanoscale insight into early reaction mechanisms. We demonstrate that the formation and growth of C-S-H precipitates starts through lateral growth of planar silicate sheets, but soon continues in all directions resulting in a 3D microstructure. Furthermore, nanocrystalline C-S-H structures with sizes between 5 nm to 10 nm were observed inside the amorphous or highly disordered C-S-H matrix, denoting that C-S-H growth is conformed to layered structure model. Crack formation and propagation inside C-S-H precipitates confirms the presence of increasing lattice strain due to growing defects that limits the growth of a fully crystalline structure by buckling and separating the sheets. The rolling up and crumbling of C-S-H sheets promotes the formation of new embryos, leading to the growth of precipitates in all direction and finally their coalescence.
{"title":"Liquid Cell Transmission Electron Microscopy Reveals C-S-H Growth Mechanism During Portland Cement Hydration","authors":"P. Dong, A. Allahverdi, C. Andrei, N. Bassim","doi":"10.2139/ssrn.3940187","DOIUrl":"https://doi.org/10.2139/ssrn.3940187","url":null,"abstract":"We report the first application of in-situ liquid cell transmission electron microscopy (LC-TEM) to research hydration reactions of nano OPC, providing nanoscale insight into early reaction mechanisms. We demonstrate that the formation and growth of C-S-H precipitates starts through lateral growth of planar silicate sheets, but soon continues in all directions resulting in a 3D microstructure. Furthermore, nanocrystalline C-S-H structures with sizes between 5 nm to 10 nm were observed inside the amorphous or highly disordered C-S-H matrix, denoting that C-S-H growth is conformed to layered structure model. Crack formation and propagation inside C-S-H precipitates confirms the presence of increasing lattice strain due to growing defects that limits the growth of a fully crystalline structure by buckling and separating the sheets. The rolling up and crumbling of C-S-H sheets promotes the formation of new embryos, leading to the growth of precipitates in all direction and finally their coalescence.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"31 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78043271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the effect of the incorporation of doping ions into the structure, thermal properties and chemical durability of bioactive glasses is fundamental for the design of new compositions with tailored biological functions and applications.In this work, we have applied a combined experimental and computational approach to unravel the effect of adding metal oxides of Ce, Ti, V, Mn, Fe, Co, Cu and Zr that impart catalase mimetic activity to the 45S5 Bioglass on its density, thermal properties and chemical durability.UV-Vis-NIR spectroscopy and temperature programmed reduction (TPR) experiments allowed to determine the oxidation states of the doping cations in the bulk of the glasses, Differential Thermal Analysis have been used to determine the glass transition and crystallization temperatures whereas the chemical durability in water was determined by following the hydrolytic resistance of glass grains at 98°C standard method.The experimental results have been interpreted at the atomic level by exploiting reliable bulk and surface structural models of the investigated glass generated by using Molecular Dynamics Simulations.Some structure-property relationships helpful for the rational design of new glass compositions have been also inferred.
{"title":"The Effect of the Incorporation of Catalase Mimetic Activity Cations on the Structural, Thermal and Chemical Durability Properties of the 45S5 Bioglass®","authors":"G. Malavasi, A. Pedone","doi":"10.2139/ssrn.3920956","DOIUrl":"https://doi.org/10.2139/ssrn.3920956","url":null,"abstract":"Understanding the effect of the incorporation of doping ions into the structure, thermal properties and chemical durability of bioactive glasses is fundamental for the design of new compositions with tailored biological functions and applications.In this work, we have applied a combined experimental and computational approach to unravel the effect of adding metal oxides of Ce, Ti, V, Mn, Fe, Co, Cu and Zr that impart catalase mimetic activity to the 45S5 Bioglass on its density, thermal properties and chemical durability.UV-Vis-NIR spectroscopy and temperature programmed reduction (TPR) experiments allowed to determine the oxidation states of the doping cations in the bulk of the glasses, Differential Thermal Analysis have been used to determine the glass transition and crystallization temperatures whereas the chemical durability in water was determined by following the hydrolytic resistance of glass grains at 98°C standard method.The experimental results have been interpreted at the atomic level by exploiting reliable bulk and surface structural models of the investigated glass generated by using Molecular Dynamics Simulations.Some structure-property relationships helpful for the rational design of new glass compositions have been also inferred.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"12 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78499073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Claudius Dichtl, D. Lunt, M. Atkinson, R. Thomas, Adam Plowman, Bartosz Barzdajn, R. Sandala, J. Q. da Fonseca, M. Preuss
Near-α titanium alloys are known to be susceptible to cold dwell fatigue (CDF), a failure mechanism that has been linked to cold creep during high-load dwell times superimposed onto low cycle fatigue loading. In order to shed new light on the deformation mechanisms during cold dwell and to understand better the role of the microstructure, two different bimodal microstructures (fine and coarse transformation product) of TIMETAL®834 were investigated at stress levels below the 0.2% proof stress using a combination of grain orientation mapping and in-situ electron microscopy imaging. This enabled in-depth analysis of 2D slip patterns and slip system activity using High-Resolution Digital Image Correlation (HRDIC), showing that in both microstructures basal slip is initially the dominant slip mode before prismatic slip activity increases approaching the 0.2% proof stress. Comparing the two constituents in the bimodal microstructure, first slip bands are localised predominantly in primary α grains, indicating higher strength of secondary α colonies, particularly for finer transformation products. During 10-minute load holds at stresses below 0.2% proof stress, more plastic strain and longer connected slip traces across several grains were observed in the sample with coarse transformation product, indicating higher susceptibility to cold creep deformation.
{"title":"Slip Activity During Low-Stress Cold Creep Deformation in a Near-Α Titanium Alloy","authors":"Claudius Dichtl, D. Lunt, M. Atkinson, R. Thomas, Adam Plowman, Bartosz Barzdajn, R. Sandala, J. Q. da Fonseca, M. Preuss","doi":"10.2139/ssrn.3919747","DOIUrl":"https://doi.org/10.2139/ssrn.3919747","url":null,"abstract":"Near-α titanium alloys are known to be susceptible to cold dwell fatigue (CDF), a failure mechanism that has been linked to cold creep during high-load dwell times superimposed onto low cycle fatigue loading. In order to shed new light on the deformation mechanisms during cold dwell and to understand better the role of the microstructure, two different bimodal microstructures (fine and coarse transformation product) of TIMETAL®834 were investigated at stress levels below the 0.2% proof stress using a combination of grain orientation mapping and in-situ electron microscopy imaging. This enabled in-depth analysis of 2D slip patterns and slip system activity using High-Resolution Digital Image Correlation (HRDIC), showing that in both microstructures basal slip is initially the dominant slip mode before prismatic slip activity increases approaching the 0.2% proof stress. Comparing the two constituents in the bimodal microstructure, first slip bands are localised predominantly in primary α grains, indicating higher strength of secondary α colonies, particularly for finer transformation products. During 10-minute load holds at stresses below 0.2% proof stress, more plastic strain and longer connected slip traces across several grains were observed in the sample with coarse transformation product, indicating higher susceptibility to cold creep deformation.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88430329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Chatterjee, Md. Basiruddin Sk, Abhijit Ghosh, R. Mitra, D. Chakrabarti
A modified 9Cr-1Mo steel having lath martensitic microstructure has been subjected to the hot-rolling at three different temperatures followed by a normalization at 1025 °C to form different crystallographic textures after thermomechanical processing. The samples hot-rolled at 875 °C, 1000 °C and 1050 °C showed major texture components as Goss (i.e. {110}<001>), Cube (i.e. {001}<0‾10>) and Gamma (i.e. {111}<‾1‾12>), respectively. Next, these samples have been uniaxial tensile tested at quasi-static strain rate at room temperature, and tensile properties are evaluated. The results indicated almost similar strength levels for Goss and Cube oriented specimens, and significantly reduced strength for Gamma oriented samples. However, the Cube and Goss oriented samples showed different strain hardening rates owing to the occurrence of deformation induced twinning and anti-twinning phenomenon as revealed by the Visco-plastic self-consistent polycrystal plasticity simulations. Simulation results were validated with experimental observations using high-resolution transmission electron microscopy. Anisotropic parameters have also been simulated considering the difference in initial crystallographic orientations. Study of deformation micro-mechanism at different length scale of martensitic units (e.g., prior-austenite grain, martensitic packets, block, sub-block, and laths) revealed negligible rotations at the prior-austenite grain level, whilst the lattice rotations were found to be significant at martensitic sub-block length scale. The investigation indicated that some specific types of martensitic variants generally participated in large lattice rotation during deformation for differently textured samples.
{"title":"Combining Crystal Plasticity and Electron Microscopy to Elucidate Texture Dependent Micro-Mechanisms of Tensile Deformation in Lath Martensitic Steel","authors":"A. Chatterjee, Md. Basiruddin Sk, Abhijit Ghosh, R. Mitra, D. Chakrabarti","doi":"10.2139/ssrn.3878355","DOIUrl":"https://doi.org/10.2139/ssrn.3878355","url":null,"abstract":"A modified 9Cr-1Mo steel having lath martensitic microstructure has been subjected to the hot-rolling at three different temperatures followed by a normalization at 1025 °C to form different crystallographic textures after thermomechanical processing. The samples hot-rolled at 875 °C, 1000 °C and 1050 °C showed major texture components as Goss (i.e. {110}<001>), Cube (i.e. {001}<0‾10>) and Gamma (i.e. {111}<‾1‾12>), respectively. Next, these samples have been uniaxial tensile tested at quasi-static strain rate at room temperature, and tensile properties are evaluated. The results indicated almost similar strength levels for Goss and Cube oriented specimens, and significantly reduced strength for Gamma oriented samples. However, the Cube and Goss oriented samples showed different strain hardening rates owing to the occurrence of deformation induced twinning and anti-twinning phenomenon as revealed by the Visco-plastic self-consistent polycrystal plasticity simulations. Simulation results were validated with experimental observations using high-resolution transmission electron microscopy. Anisotropic parameters have also been simulated considering the difference in initial crystallographic orientations. Study of deformation micro-mechanism at different length scale of martensitic units (e.g., prior-austenite grain, martensitic packets, block, sub-block, and laths) revealed negligible rotations at the prior-austenite grain level, whilst the lattice rotations were found to be significant at martensitic sub-block length scale. The investigation indicated that some specific types of martensitic variants generally participated in large lattice rotation during deformation for differently textured samples.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80445062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Alaghmandfard, M. Mahdavi, P. Seraj, H. Pirgazi, Dharmendra Chalasani, B. S. Amirkhiz, L. Kestens, A. Odeshi, S. Liang, H. Garmestani, M. Mohammadi
Two different Ti-6Al-4V cylindrical rods, horizontally and vertically built, fabricated through the electron beam melting technique, were underwent compression loadings to failure at the strain rates of 2350s-1 and 1750s-1, respectively. Low-angle grain boundary formation, dislocation array, and dislocation pinning were observed and attributed to the stress-induced dislocation formation in the as-built microstructure. Superior strength at each strain rate in vertically built samples was concluded to be a consequence of its finer microstructure and the presence of martensite α'. Hardness measurements revealed higher values at the areas close to the fracture surface. Electron microscopic characterization revealed parallel-twin formation resulting from adiabatic temperature rise, increasing short-ranged clustering, and the high stacking fault energy. Dynamic compressive deformation led to the appearance of dislocation structure, cell blocks, and extended dislocation walls formation. Texture analysis showed type pyramidal slip systems and contraction twins as the most favorable slip systems. Texture evolution interpretations from the region far from the area close to the fractured surface indicated that mean grain size decreased, and higher dislocation densities were obtained. The more preferred texture tended to rotate by approaching the fracture surface so that the basal plane became parallel to the fracture surface, which is directly related to the facilitation of crack propagation. Moreover, the generalized spherical harmonics were used to apply 2-point statistics on the texture and then statistically compare the texture changes. The results were in good agreement statistically, where principal components (PC) were utilized to explain variances in the database.
{"title":"Characterization and Statistical Modeling of Texture and Microstructure Evolution in Dynamically Fractured Electron Beam Melted Ti-6Al-4V","authors":"R. Alaghmandfard, M. Mahdavi, P. Seraj, H. Pirgazi, Dharmendra Chalasani, B. S. Amirkhiz, L. Kestens, A. Odeshi, S. Liang, H. Garmestani, M. Mohammadi","doi":"10.2139/ssrn.3949514","DOIUrl":"https://doi.org/10.2139/ssrn.3949514","url":null,"abstract":"Two different Ti-6Al-4V cylindrical rods, horizontally and vertically built, fabricated through the electron beam melting technique, were underwent compression loadings to failure at the strain rates of 2350s-1 and 1750s-1, respectively. Low-angle grain boundary formation, dislocation array, and dislocation pinning were observed and attributed to the stress-induced dislocation formation in the as-built microstructure. Superior strength at each strain rate in vertically built samples was concluded to be a consequence of its finer microstructure and the presence of martensite α'. Hardness measurements revealed higher values at the areas close to the fracture surface. Electron microscopic characterization revealed parallel-twin formation resulting from adiabatic temperature rise, increasing short-ranged clustering, and the high stacking fault energy. Dynamic compressive deformation led to the appearance of dislocation structure, cell blocks, and extended dislocation walls formation. Texture analysis showed type pyramidal slip systems and contraction twins as the most favorable slip systems. Texture evolution interpretations from the region far from the area close to the fractured surface indicated that mean grain size decreased, and higher dislocation densities were obtained. The more preferred texture tended to rotate by approaching the fracture surface so that the basal plane became parallel to the fracture surface, which is directly related to the facilitation of crack propagation. Moreover, the generalized spherical harmonics were used to apply 2-point statistics on the texture and then statistically compare the texture changes. The results were in good agreement statistically, where principal components (PC) were utilized to explain variances in the database.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72872326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Q. Xie, Zhiran Yan, Dunji Yu, K. An, Xingchen Yan, Shuo Yin, Xiaolong Wu, P. Yang, Zhengzhi Zhao, Yandong Wang
In-situ neutron diffraction investigation on a high manganese steel, which was stretched before or after the fatigue loading, renders a meso-scale damage criterion: the {111} and {422} lattice strains along the transverse direction violating the Poisson effect signifies severe damage. They either showed no more lattice contraction corresponding to increasing of the tensile stress or transversal expansion during the plastic stage of tension. Distribution of the damaged grains was further investigated by the full-width at half-maximum pole figures. The crystal plasticity simulations justify the rationality of the damage criterion, and it could relate to the orientation distribution of the damaged slip/twinning planes. The cracks mainly distributed at the transverse surface. It is shown that the strong interaction between twin boundaries and slip dislocations could result in heavy damage at the surface, with a morphology of curved twin boundaries. Also, grain boundaries and the narrow deformation twins often correspond to different amplitudes of transversal contraction and expansion than other surface areas during the tension-compression fatigue loading, which may trigger the surface cracks. It is due to large crystallographic orientation gradients. The present paper provides a sound routine to identify criterions of the plastic damage for face-centered-cubic (FCC) polycrystals.
{"title":"Crystallographic Orientation and Spatially Resolved Damage for Polycrystalline Deformation of a High Manganese Steel","authors":"Q. Xie, Zhiran Yan, Dunji Yu, K. An, Xingchen Yan, Shuo Yin, Xiaolong Wu, P. Yang, Zhengzhi Zhao, Yandong Wang","doi":"10.2139/ssrn.3890356","DOIUrl":"https://doi.org/10.2139/ssrn.3890356","url":null,"abstract":"In-situ neutron diffraction investigation on a high manganese steel, which was stretched before or after the fatigue loading, renders a meso-scale damage criterion: the {111} and {422} lattice strains along the transverse direction violating the Poisson effect signifies severe damage. They either showed no more lattice contraction corresponding to increasing of the tensile stress or transversal expansion during the plastic stage of tension. Distribution of the damaged grains was further investigated by the full-width at half-maximum pole figures. The crystal plasticity simulations justify the rationality of the damage criterion, and it could relate to the orientation distribution of the damaged slip/twinning planes. The cracks mainly distributed at the transverse surface. It is shown that the strong interaction between twin boundaries and slip dislocations could result in heavy damage at the surface, with a morphology of curved twin boundaries. Also, grain boundaries and the narrow deformation twins often correspond to different amplitudes of transversal contraction and expansion than other surface areas during the tension-compression fatigue loading, which may trigger the surface cracks. It is due to large crystallographic orientation gradients. The present paper provides a sound routine to identify criterions of the plastic damage for face-centered-cubic (FCC) polycrystals.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78058898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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