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Phase transformation and structural evolution in a Ti-5at.%Al alloy induced by cold-rolling

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Journal of Materials Science & Technology 2020年第14期47卷 211-223页

作者： Bingqiang Wei Song Ni Yong Liu Xiaozhou Liao Min Song State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The phase transformation,deformation mechanism and their correlation in a cold-rolled Ti-5 at.%Al alloy were investigated.Two types of phase transformations from a hexagonal close-packed(HCP)structure to a face-centered cubic(FCC)structure were observed:the basal-type(B-type)with an orientation relation-ship ofaxis of the HCP matrix.With the proceeding of deformation,different deformation mechanisms were activated in the FCC and the HCP structures,respectively,which led to a faster grain refinement rate in the FCC structure than in the HCP matrix.Deformation twins with zero macroscopic strain were prevalent in the FCC domains produced by the B-type transformation,while deformation twins with macroscopic strain were normally observed in the FCC domains produced by the P-type transformation.This is in accordance with the lattice mismatches produced during phase transformation.The easy occurrence of deformation twinning in the FCC structure contributed significantly to the grain refinement process.In addition,the interaction between neighboring FCC domains produced by the two types of phase transformations also accelerated the grain refinement process.

关键词： Ti-Al alloy Deformation mechanism Phase transformation Grain refinement Deformation twinning

Harnessing nature's biosynthetic capacity to facilitate total synthesis

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National Science Review 2022年第11期9卷 16-18页

作者： Haili Zhang Ge liao xiaozhou Luo Xiaoyu Tang Institute of Chemical Biology Shenzhen Bay Laboratory Center for Synthetic Biochemistry Shenzhen Institute of Synthetic Biology Shenzhen Institute of Advanced TechnologyChinese Academy of Sciences

Natural products (NPs) have long piqued the interests of chemists due to their structural complexity. More importantly, evolution has conferred NPs with the ability to interact with biological macromolecules (such as nucleic acids, proteins, carbohydrates and lipids), making them privileged scaffolds for drug discovery. Until now,

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Composition-dependent dynamic precipitation and grain refinement in Al-Si system under high-pressure torsion

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Journal of Materials Science & Technology 2021年第9期68卷 199-208页

作者： Shenbao Jin Zhenjiao Luo Xianghai An Xiaozhou Liao Jiehua Li Gang Sha Herbert Gleiter Institute of Nanoscience School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing210094 China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneyNSW2006Australia Institute of Casting Research Montanuniversitat LeobenA-8700LeobenAustria

Understanding composition effects is crucial for alloy design and development. To date, there is a lack of research comprehensively addressing the effect of alloy composition on dynamic precipitation, segregation and grain refinement under severe-plastic-deformation processing. This research investigates Al-x Si alloys with x = 0.1, 0.5 and 1.0 at.% Si processed by high pressure torsion(HPT) at room temperature by using transmission electron microscopy, transmission Kikuchi diffraction and atom probe tomography. The alloys exhibit interesting composition-dependent grain refinement and fast dynamic decomposition under HPT processing. Si atoms segregate at dislocations and Si precipitates form at grain boundaries(GBs) depending on the Si content of the alloys. The growth of Si precipitates consumes most Si atoms segregating at GBs, hence the size and distribution of the Si precipitates become predominant factors in controlling the grain size of the decomposed Al-Si alloys after HPT processing. The hardness of the Al-Si alloys is well correlated with a combination of grain-refinement strengthening and the decomposition-induced softening.

关键词： Al-Si alloys Composition effects Dynamic precipitation Solute segregation Grain refinement

Effects of temperature and alloying content on the phase transformation and{10■1}twinning in Zr during rolling

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Journal of Materials Science & Technology 2020年第6期41卷 76-80页

作者： Xinglong An Hao Zhang Song Ni Xiaoqin Ou Xiaozhou Liao Min Song State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The effects of temperature and Ti content on the deformation mechanisms of pure Zr and Zr-Ti alloys were investigated by transmission electron microscopy.The results indicate the existence of a relation between deformation-induced phase transformation from a hexagonal close-packed structure to a facecentered cubic structure and{10■1}deformation twinning.That is,when one is suppressed,the other will be promoted.The phase transformation was suppressed while the{10■1}compressive twinning was promoted with increasing the rolling temperature and/or Ti content.This can be attributed to the activation of basaldislocations at high temperature and the increased stacking fault energy with Ti content.

关键词： Zr Zr-Ti alloy Twinning Phase transformation Stacking fault energy

Ultrastrong and ductile(CoCrNi)_(94)Ti_(3)Al_(3)medium-entropy alloys via introducing multi-scale heterogeneous structures

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Journal of Materials Science & Technology 2023年第4期135卷 241-249页

作者： Jianying Wang Jianpeng Zou Hailin Yang Xixi Dong Peng Cao Xiaozhou Liao Zhilin Liu Shouxun Ji State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Brunel Centre for Advanced Solidification Technology(BCAST) Brunel University LondonUxbridgeMiddlesex UB83PHUnited Kingdom Department of Chemical and Materials Engineering The University of Auckland1142New Zealand School of Aerospace Mechanical&Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia Light Alloy Research Institute College of Mechanical and Electrical EngineeringCentral South UniversityChangsha 410083China

The coarsening-grained single-phase face-centered cubic(fcc)medium-entropy alloys(MEAs)normally exhibit insufficient strength for some engineering applications.Here,superior mechanical properties with ultimate tensile strength of 1.6 GPa and fracture strain of 13.1%at ambient temperature have been achieved in a(CoCrNi)_(94)Ti_(3)Al_(3)MEA by carefully architecting the multi-scale heterogeneous structures.Electron microscopy characterization indicates that the superior mechanical properties mainly originated from the favorable heterogeneous fcc matrix(1-40μm)and the coherent sphericalγ’precipitates(10-100 nm),together with a high number density of crystalline defects(2-10 nm),including dislocations,small stacking faults,Lomer-Cottrell locks,and ultrafine deformation twins.

关键词： Medium-entropy alloys Mechanical properties Heterogeneous structure γ’nanoprecipitates Crystalline defects

Understanding formation of Mg-depletion zones in Al-Mg alloys under high pressure torsion

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Journal of Materials Science & Technology 2019年第5期35卷 858-864页

作者： Jing Xue Shenbao Jin Xianghai An Xiaozhou Liao Jiehua Li Gang Sha Herbert Gleiter Institute of Nanoscience School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China School of Aerospace Mechanical and Mechatronic Engineering The University of Sydney Sydney NSW 2006 Australia Institute of Casting Research Montanuniversitat Leoben A-8700 Leoben Austria

Redistribution of elements may take place in alloys during severe plastic deformation, which significantly alters the mechanical properties of the alloys. Therefore, comprehensive knowledge about deformationinduced redistribution of elements has to be established. In the present paper, the distribution of Mg in an Al-Mg alloy processed by high pressure torsion was examined using atom probe tomography(APT).With crystallographic information extracted by APT data analysis, this research reveals that the movement of dislocations plays an important role in the formation of Mg-depletion zones in the deformed microstructure.

关键词： High-pressure torsion Atom probe tomography Aluminum alloys Grain boundary diffusion Dislocation

Ultra-strong and thermally stable nanocrystalline CrCoNi alloy

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Journal of Materials Science & Technology 2022年第11期106卷 1-9页

作者： Peng Gao Shuo Sun Heng Li Ranming Niu Shuang Han Hongxiang Zong Hao Wang Jianshe Lian Xiaozhou Liao School of Aerospace Mechanical&Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

Grain refinement to the nanocrystalline regime is the most effective way to strengthen materials but this often deteriorates the grain-size thermal stability and plasticity. Here we manufactured a nanocrystalline face centred cubic Cr Co Ni medium entropy alloy with columnar grains via magnetron sputtering. Compression of CrCoNi pillars with diameters of ~1 μm revealed a record high yield strength of ~5 GPa for pillars with face centred cubic structures and engineering plastic strain of > 30%. The alloy possessed an outstanding grain-size thermal stability even at 1073 K. Both nanocrystalline grain size and a high density of nanotwins/stacking faults are critical to the exceptional yield strength. Deformation twinning, grains refinement during deformation, grain boundary sliding and random grain orientation all contribute to the large plasticity. The outstanding thermal stability is attributed to the sluggish diffusion effect and the low energy of twin boundaries.

关键词： Medium entropy alloy CrCoNi Nanocrystalline In-situ microscopy Mechanical properties Thermal stability

Unveiling the grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy

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Journal of Materials Science & Technology 2022年第32期127卷 98-107页

作者： Shuo Sun Yang Yang Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys.

关键词： Medium-entropy alloy Nanocrystalline Nanoindentation Incipient plasticity Grain boundary

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筒体支耳连接结构局部刚度计算及特性分析

核动力工程 2023年第5期44卷 104-109页

作者：江小州廖国江叶献辉刘帅黄旋彭向峰中国核动力研究设计院核反应堆系统设计技术重点实验室成都610213

核电厂反应堆系统中典型筒体支耳连接结构的局部刚度准确计算具有重要的工程意义。本文建立了筒体支耳连接结构的三维有限元模型,分析得到了有限元计算总位移,并给出由集中力和扭矩分别引起的梁式位移计算方法,从而求解梁式总位移,进而... 详细信息

核电厂反应堆系统中典型筒体支耳连接结构的局部刚度准确计算具有重要的工程意义。本文建立了筒体支耳连接结构的三维有限元模型,分析得到了有限元计算总位移,并给出由集中力和扭矩分别引起的梁式位移计算方法,从而求解梁式总位移,进而得到筒体支耳连接结构的局部刚度。通过建立筒体支耳连接结构的分解模型进行局部刚度计算,探讨了与整体模型局部刚度计算结果的差异。采用整体模型计算方法,选取不同的边界面进行局部刚度计算,得到了相应的局部刚度变化规律,同时通过调整支耳角度研究其对局部刚度特性的影响。本文研究可为筒体支耳连接结构工程设计提供参考。

关键词：筒体支耳连接结构梁式位移局部刚度边界面选取支耳角度