AMI: Acta Materialia最新文献_第8页

The Influence of Microstructural Texture and Prior Beta Grain Recrystallisation on the Deformation Behaviour of Laser Powder Bed Fusion Produced Ti-6al-4v 显微组织织构和预先β晶粒再结晶对激光粉末床熔合Ti-6al-4v变形行为的影响

AMI: Acta Materialia Pub Date : 2020-01-01 DOI: 10.2139/ssrn.3694108

G. T. Haar, T. Becker

{"title":"The Influence of Microstructural Texture and Prior Beta Grain Recrystallisation on the Deformation Behaviour of Laser Powder Bed Fusion Produced Ti-6al-4v","authors":"G. T. Haar, T. Becker","doi":"10.2139/ssrn.3694108","DOIUrl":"https://doi.org/10.2139/ssrn.3694108","url":null,"abstract":"The control and predictability of mechanical properties during manufacturing is essential in achieving parts that consistently deliver adequate mechanical properties. In laser powder bed fusion produced Ti-6Al-4V, this control is complex and dependent on the build orientation. While studies have identified the columnar prior-β grain structure as a cause in mechanical anisotropy, differences in underlying micro-structure and its influence on anisotropy are not yet well understood. This study investigates micro-structural texture differences in two build orientations before and after post-process heat treatments and in what way the micro-structural features control deformation-and-failure behavior. The study uses uniaxial tensile tests to determine tensile behavior of samples built “vertically” and “horizontally” with reference to the build plate. Microscopy techniques of scanning electron microscopy imaging and back-scatter diffraction are used for micro-structure characterization and deformation mode identification. Results identify key crystallographic and morphological textural differences in the two build-orientations. Heat treatments above the β-transus successfully globularise prior β grains, thereby improving mechanical anisotropy. The use of electron backscatter diffraction demonstrates key morphological features that control slip, micro-crack initiation and final fracture.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86861887","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}

引用次数: 1

Detection of the LLT in Superalloys Melts Upon Overheating and Relaxation by the Electromagnetic Method 电磁法检测高温合金熔体过热松弛时的LLT

AMI: Acta Materialia Pub Date : 2020-01-01 DOI: 10.2139/ssrn.3674669

A. Tyagunov, G. Tyagunov, O. Milder, D. Tarasov

{"title":"Detection of the LLT in Superalloys Melts Upon Overheating and Relaxation by the Electromagnetic Method","authors":"A. Tyagunov, G. Tyagunov, O. Milder, D. Tarasov","doi":"10.2139/ssrn.3674669","DOIUrl":"https://doi.org/10.2139/ssrn.3674669","url":null,"abstract":"Among numerous melt structure model representations, the most relevant for liquid heat-resistant nickel alloys description is the quasicrystalline model of microinhomogeneous structure, in which it is assumed that multicomponent nickel melts consist of clusters and intercluster space. Clusters inherit the short-range order of the atomic structure from various phases of the initial solid metal crystalline structure. Heating the melt to a certain temperature and/or increasing a period of its isothermal holding at constant pressure leads to a second-order phase LLT transition. As a result, atomic associations which are more balanced and uniformly distributed over the melt volume are formed. Structural changes in nickel superalloy melts are irreversible and have a significant effect on the formation of the structure and properties of a solid metal during crystallization. Structural LLT changes in multicomponent nickel melts are the basis for the scientific substantiation of technological modes of smelting, which contribute to improving the technological properties of melts, reducing metallurgical defects, the rational use of expensive elements and foundry waste, as well as, a significant improvement in the quality of metal products. This work is devoted to the experimental determination of the LLT transition in superalloy melts by the noninvasive electromagnetic method.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83987712","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}

引用次数: 0

Part I: A Study of the Underlying Factor(s) Effecting the Change of Point of Zero Charge With Decreasing Particle Size 第一部分:影响零电荷点随粒径减小而变化的潜在因素研究

AMI: Acta Materialia Pub Date : 2020-01-01 DOI: 10.2139/ssrn.3910605

M. Leffler, Anne Mirich, S. Suib

引用次数: 0

New Insights into the Formation Mechanism of Solid-Liquid Segregation in the Semi-Solid Processing: Macro-Micro Linkage Theory 半固态加工中固液偏析形成机理的新认识:宏观-微观联系理论

AMI: Acta Materialia Pub Date : 2020-01-01 DOI: 10.2139/ssrn.3708673

W. Qu, Da-quan Li, Xiaogang Hu, Min Luo, Q. Zhu

{"title":"New Insights into the Formation Mechanism of Solid-Liquid Segregation in the Semi-Solid Processing: Macro-Micro Linkage Theory","authors":"W. Qu, Da-quan Li, Xiaogang Hu, Min Luo, Q. Zhu","doi":"10.2139/ssrn.3708673","DOIUrl":"https://doi.org/10.2139/ssrn.3708673","url":null,"abstract":"Solid-liquid segregation is a typical problem in multiphase flow, especially in the die casting of metallic alloys. The avoidance of phase segregation in High Pressure Die Casting (HPDC), and Semi-solid Processing (SSP) for suspended flow is a benefit for improving product performance. At present, there is not a unified statement on the cause of the solid-liquid segregation defect. The formation mechanism of phase segregation is investigated by theoretical analysis from the perspective of hydrodynamic and rheology. The relationship between hydrodynamic parameters and characteristic rheological index is established. Maps of critical velocity, power-law index n, and consistency coefficient k are depicted for the semi-solid slurries. Then experiments and corresponding multiphase simulations were conducted to verify this theory. The macroscopic and microscopic linkage mechanism was proposed based on the theoretical discussion. This investigation not only provides important insights into the flow map of the semi-solid slurry, but also offers a key criterion of filling velocity for the avoiding of phase segregation for shear-thinning non-Newtonian fluids.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"119 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73663980","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}

引用次数: 0

4D Imaging of Void Nucleation, Growth and Coalescence from Large and Small Inclusions in Steel 钢中大小夹杂物空洞形核、生长和聚结的4D成像

AMI: Acta Materialia Pub Date : 2019-11-20 DOI: 10.2139/ssrn.3490434

Yi Guo, T. Burnett, S. McDonald, M. Daly, A. Sherry, P. Withers

{"title":"4D Imaging of Void Nucleation, Growth and Coalescence from Large and Small Inclusions in Steel","authors":"Yi Guo, T. Burnett, S. McDonald, M. Daly, A. Sherry, P. Withers","doi":"10.2139/ssrn.3490434","DOIUrl":"https://doi.org/10.2139/ssrn.3490434","url":null,"abstract":"Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst simultaneously imaged in 3D in real time using high resolution, high frame rate time-lapse synchrotron computed tomography (CT). This enabled direct observation of void development from nucleation, through growth to coalescence and final failure validating many inferences made post mortem or by theoretical models, as well as raising new points. The sparse, large inclusions were found to nucleate voids at essentially zero plastic strain (consistent with zero interfacial strength); these became increasingly elongated with straining. In contrast, a high density of small spherical voids were found to nucleate from the sub-micron cementite particles at larger strains (>200%) only in the centre of the necked (high triaxiality) region. An interfacial strength approaching 2100MPa was inferred and soon after their nucleation, these small voids coalesce to form internal microcracks that lead to the final failure of the specimen. Perhaps surprisingly, under these conditions of generally low triaxial constraint the large voids are simply cut across and appear to play no significant role in determining the final failure. The implications of these results are discussed in terms of ductile fracture behaviour and the Gurson model for ductile fracture.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"79 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79075322","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}

引用次数: 2

AMI: Acta Materialia Pub Date : 2019-10-23 DOI: 10.2139/ssrn.3474536

Gareoung Kim, M. Lee, J. Yun, Soon-Gil Jung, Woongjin Choi, T. You, J. Rhyee

{"title":"Strongly Correlated and Strong Coupled S-Wave Superconductivity of the High Entropy Alloy Ta 1/6Nb 2/6Hf 1/6Zr 1/6Ti 1/6 Compound","authors":"Gareoung Kim, M. Lee, J. Yun, Soon-Gil Jung, Woongjin Choi, T. You, J. Rhyee","doi":"10.2139/ssrn.3474536","DOIUrl":"https://doi.org/10.2139/ssrn.3474536","url":null,"abstract":"High entropy alloy (HEA) is a random mixture of multiple elements stabilized by a high mixing entropy. We synthesized Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 bulk HEA compound as a body-centered cubic structure with the lattice parameter a = 3.38 Å by arc melting. From the electronic and magnetic properties measurements, we found that it exhibits a superconducting transition at Tc = 7.85 K. From the superconducting properties such as electron-phonon coupling constant λel-ph, electron-phonon potential Vel-ph, density of states at the Fermi level D(EF), superconducting energy gap 2Δ(0)/kBTc, upper-critical field Hc2(0), coherence length ξ, and critical current Jc etc, we found that it is a strong coupled s-wave superconductor in a dirty limit. Meanwhile, the relative sizeable specific heat jump (ΔC/γTc), high effective mass of carrier (29 me), and high Kadowaki-Woods ratio which is close to one of heavy Fermi compounds indicate that it resides in the limit of a strongly correlated system. The vortex pinning force is described by the Dew-Huges double exponential pinning model, implying that there are two types of pinning mechanism. The possible coexistence of strongly correlated behavior in s-wave superconductivity on the HEA compounds is noteworthy because many of the strongly correlated superconductors have a nodal gap symmetry such as heavy fermion and high Tc cuprate superconductors. The HEA compound suggests a different types of superconductivity with the current strongly correlated superconductors as well as metallic superconductors.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74993053","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}

引用次数: 3

Atomic-Scale Insight into the Reversibility of Polar Order in Ultrathin Epitaxial Nb:SrTiO 3/BaTiO 3 Heterostructure and Its Implication to Resistive Switching 超薄外延Nb: srtio3 / batio3异质结构极性顺序可逆性的原子尺度研究及其对电阻开关的意义

AMI: Acta Materialia Pub Date : 2019-10-23 DOI: 10.2139/ssrn.3474533

J. Yao, M. Ye, Yuanwei Sun, Ye Yuan, H. Fan, Yuan Zhang, Chao Chen, Cong Liu, K. Qu, Gaokuo Zhong, Tingting Jia, Z. Fan, Shanming Ke, Yue Zhao, Chungang Duan, Peng Gao, Jiangyu Li

{"title":"Atomic-Scale Insight into the Reversibility of Polar Order in Ultrathin Epitaxial Nb:SrTiO 3/BaTiO 3 Heterostructure and Its Implication to Resistive Switching","authors":"J. Yao, M. Ye, Yuanwei Sun, Ye Yuan, H. Fan, Yuan Zhang, Chao Chen, Cong Liu, K. Qu, Gaokuo Zhong, Tingting Jia, Z. Fan, Shanming Ke, Yue Zhao, Chungang Duan, Peng Gao, Jiangyu Li","doi":"10.2139/ssrn.3474533","DOIUrl":"https://doi.org/10.2139/ssrn.3474533","url":null,"abstract":"Ferroelectric heterostructures with bi-stable state of polarization are appealing for data storage as well as tunable functionalities such as memristor behavior. While an increasing number of experimental and theoretical studies suggest that polarization persists in ultrathin epitaxial heterostructures approaching just a couple of unit cells, the switching of such polar order is much less well understood, and whether polarization can be reversed in ultrathin ferroelectric heterostructures remains to be answered. Here we fabricate high-quality 7-unit cell thick BaTiO3 (BTO) films on Nb-doped single crystalline SrTiO3 (NSTO) substrate, and demonstrate their apparent yet unambiguously false polarization reversal due to charge injection using comprehensive piezoresponse force microscopy (PFM) studies. The presence of weak polar order consistent with linear piezoelectricity is confirmed at the atomic scale by high resolution integrated differential phase contrast (IDPC) of transmission electron microscopy (TEM) as well as macroscopic second harmonic generation (SHG), while the lack of polarization reversal under the voltage applied is supported by density functional theory calculation showing the persistence of dead layer on the surface. Nevertheless, poling-induced electric conduction differing by two orders of magnitude is observed, demonstrating resistive switching in ferroelectric heterostructure in the absence of polarization reversal, even with weak polar order. Our finding has technological implications on emerging memristor applications with potentially more accessible states than bi-stable polarization modulated mechanism, and raises technical challenges to unambiguously demonstrate polarization switching in ultrathin films at their critical size limit.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74937019","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}

引用次数: 2

Neutron Diffraction Study on Full-Shape Japanese Sword 全形日本刀的中子衍射研究

AMI: Acta Materialia Pub Date : 2019-05-21 DOI: 10.2139/ssrn.3391539

S. Harjo, T. Kawasaki, F. Grazzi, T. Shinohara, Manako Tanaka

{"title":"Neutron Diffraction Study on Full-Shape Japanese Sword","authors":"S. Harjo, T. Kawasaki, F. Grazzi, T. Shinohara, Manako Tanaka","doi":"10.2139/ssrn.3391539","DOIUrl":"https://doi.org/10.2139/ssrn.3391539","url":null,"abstract":"Abstract A mapping measurement using pulsed neutron diffraction with time-of-flight method is performed on a full-shape Japanese sword made in Keicho era (1596–1615) to elucidate the manufacturing process. The obtained diffraction patterns are analyzed by the Rietveld refinement and a line profile analysis. The constituent phases in the area closer to the back of the blade (ridge) are found to be ferrite and cementite, composing pearlite, while the area close to the edge is composed by martensite and austenite. The distributions of constituent phases are well explained with the distributions of dislocation density and crystallite size. The carbon contents in the area closer to the ridge side estimated from the phase fraction of cementite and in the area closer to the edge side considered from the phase fraction of austenite are similar, 0.9–1.0 mass%, expecting that the Japanese sword used in this study was created by the technique of maru, i.e., the use of a single type of high-carbon steel for the whole volume. The residual macroscopic stresses are estimated from the obtained lattice parameters of constituent phases. The distributions of residual macroscopic stresses in the width and thickness directions are small. The stress in the longitudinal direction is compressive at the ridge side, turns to quite large tensile at the middle part of width, then drastically decreases to be quite large compressive at the edge side of about −650 MPa.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87666266","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}

引用次数: 11

High Temperature Deformation Mechanisms in WC-Ni 3Al Cermets WC-Ni - 3Al陶瓷的高温变形机理

AMI: Acta Materialia Pub Date : 2019-05-20 DOI: 10.2139/ssrn.3390934

Minai Zhang, A. Dupuy, Jingmao Li, Xin Wang, S. Qu, J. Schoenung, Xiaoqiang Li

引用次数: 0

Second-Order-Transition Like Characteristic and its Contribution to Strain Temperature Stability in Multiphase Coexistent (K, Na)NbO 3-Based Materials 多相共存(K, Na)NbO - 3基材料的二阶类转变特性及其对应变温度稳定性的贡献

AMI: Acta Materialia Pub Date : 2019-04-26 DOI: 10.2139/ssrn.3378378

Gang Liu, Jie Yin, Chunlin Zhao, X. Lv, Jiagang Wu

{"title":"Second-Order-Transition Like Characteristic and its Contribution to Strain Temperature Stability in Multiphase Coexistent (K, Na)NbO 3-Based Materials","authors":"Gang Liu, Jie Yin, Chunlin Zhao, X. Lv, Jiagang Wu","doi":"10.2139/ssrn.3378378","DOIUrl":"https://doi.org/10.2139/ssrn.3378378","url":null,"abstract":"High strain and well temperature stability are contradicted in (K, Na)NbO3-based (KNN) materials. Herein, well temperature stability with high strain is obtained in multiphase coexistent KNN. Second-order-transition like characteristic contributes to the temperature stability, in which intrinsic lattice structure is the bridge between them. Similar characteristic to second order transition is caused by the reduced discrepancy among different lattice symmetries and broadening temperature region of phase transitions. These integrated factors can slow down the latent heat in first order transition and extend it over a wide temperature region, thereby exhibiting similar characteristic to second order transition. Correspondingly, the abruptly increased strain near the phase transition temperature slows down significantly. In addition, the appearance of pure tetragonal symmetry (P4mm) is deferred to a much higher temperature than TO-T (temperature of orthorhombic-tetragonal transition), in which strain will inevitably decrease. Thus, well temperature stability with high strain response is realized in multiphase coexistent KNN materials.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83025122","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}

引用次数: 0