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Impact of B alloying on ductility and phase transition in the Ni–Mn-based magnetic shape memory alloys:Insights from first-principles calculation

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Journal of Materials Science & Technology 2021年第15期74卷 27-34页

作者： Hai-Le Yan Hao-Xuan Liu Ying Zhao Nan Jia Jing Bai Bo Yang Zongbin Li Yudong Zhang Claude Esling Xiang Zhao Liang Zuo Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang 110819China State Key Lab Rolling&Automat Northeastern UniversityShenyang 110819China School of Resources and Materials Northeastern University at Qinhuangdao BranchQinhuangdao 066004China Laboratoire d'Etude des Microstructures et de Mecanique des Materiaux(LEM3) CNRS UMR 7239Universite de Lorraine57045 Metz.France

Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowledge related to B alloying is limited until now.More importantly,the mechanism of the improved ductility,which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments,is still unclear.In this context,by first-principles calculations,the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems,i.e.,(Ni_(2-x)B_(x))MnGa,Ni_(2)(Mn_(1-x)B_(x))Ga,Ni_(2)Mn(Ga_(1-x)B_(x))and(Ni_(2)MnGa)_(1-x)B_(x).Results show that B prefers the direct occupation manner when it replaces Ni,Mn and Ga.For interstitial doping,B tends to locate at octahedral rather than tetrahedral interstice.Calculations show that the replacement of B for Ga can effectively improve(reduce)the inherent ductility(inherent strength)due to the weaker covalent strength of Ni(Mn)–B compared with Ni(Mn)–Ga.In contrast,B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn)and B,bringing about a significantly improved strength and a greatly reduced ductility.Upon the substitutions for Ni and Mn,they affect both the inherent ductility and strength insignificantly.For phase transition,the replacement of B for Ga tends to destabilize the austenite,which can be understood in the picture of the band Jahn–Teller effect.Besides,the substitution for Ga would not lead to an obvious reduction of magnetization.

关键词： Magnetic shape memory alloys Boron alloying ductility Phase stability First-principles calculation

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High strength and ductility of 34CrNiMo6 steel produced by laser solid forming

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Journal of Materials Science & Technology 2019年第2期35卷 377-387页

作者： Chunping Huang Xin Lin Fencheng Liu Haiou Yang Weidong Huang State Key Laboratory of Solidification Processing Northwestern Polytechnical University Engineering Research Center in Additive Manufacturing Nanchang Hangkong University

Because of the excellent mechanical properties of 34 CrNiMo6 steel, it is widely used in high-value components. Many conventional approaches to strengthening-steels typically involve the loss of useful ductility.In this study, 34 CrNiMo6 Steel having high strength and ductility is produced by laser solid forming(LSF)with a quenching-tempering(QT) treatment. Tempering of bainite is mainly by solid phase transformation in the previous LSF layers during the LSF process. The stable microstructure of LSF consists of ferrite and fine carbides. The microstructure transfers to tempered sorbite after heat-treatment. The tensile properties of the LSF steel meet those of the wrought standard. The UTS and elongation of LSF sample at 858 MPa, 19.2%, respectively, are greater than those of the wrought. The QT treatment enhanced the ultimate tensile strength and yield strength of the LSF sample. The ultimate tensile strength, yield strength, reduction in area, and elongation of the LSF+QT sample at 980 MPa, 916 MPa, 58.9%, and 13.9%,respectively, are greater than those of the wrought standard. The yield strength of the LSF+QT sample is approximately 1.27 times that of the wrought. The LSF samples failed in a ductile fracture mode, while the LSF+QT samples showed mixed-mode failure. The defects have only a small effect on the tensile properties owing to the excellent ductility of the LSF sample.

关键词： Laser solid forming High strength and ductility Quenching and tempering steel Microstructure Mechanical property

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The role of Ca,Al and Zn on room temperature ductility and grain boundary cohesion of magnesium

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Journal of Magnesium and Alloys 2021年第5期9卷 1536-1551页

作者： Supriya Nandy Shao-Pu Tsai Leigh Stephenson Dierk Raabe Stefan Zaefferer Max-Planck Institut für Eisenforschung Düsseldorf 40237Germany

It is know from literature that small additions(<1 wt%)of Ca,Al and Zn significantly improve the intrinsic ductility of Mg.The exact role of each element,both qualitatively and quantitatively,and their combined effect... 详细信息

It is know from literature that small additions(ductility of Mg.The exact role of each element,both qualitatively and quantitatively,and their combined effects,however,are poorly understood.Here we achieved a much clearer view on the quantitative role of each element with respect to ductility improvement and on the collaborative effect,particularly of Ca and Zn in Mg.Some of our findings and conclusions are in disagreement with data and interpretation found in literature.Four different alloys,namely,Mg-0.1 Ca,Mg-0.1 Ca-1 Al,Mg-0.05 Ca-1 Al,Mg-0.1 Ca-2 Al-1 Zn(all are in wt%)were selected for this investigation.All alloys were treated such that approx.similar grain sizes and textures were obtained.This largely excludes the effect of extrinsic factors on ductility.EBSD-guided slip trace analyses reveal that the addition of Ca eases activation of prismatic and pyramidal II slip systems.Using in-situ deformation experiments in SEM and atom probe tomography observations of grain boundaries direct evidence is given for the individual and synergetic effects of Ca and Zn on grain boundary cohesion as an important contribution to improve the ductility of these alloys.We conclude that Ca reduces the slip anisotropy and ameliorates ductility,however,the weak grain boundary cohesion in the Mg-0.1 wt%Ca alloy limits the material’s tensile ductility.The addition of Zn alters the Ca segregation at the grain boundaries and helps to retain their cohesive strength,an effect which thus enables higher ductility and strength.The further addition of Al primarily improves the strength.The results show that the balanced influence of reduced slip anisotropy on the one hand and increased grain boundary cohesion on the other hand allow to design a high strength high ductility rare-earth free Mg alloy.

关键词： Magnesium–Calcium–Zinc alloys ductility Slip system determination grain boundary cohesion

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Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe–Ga rolled alloys

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 444-452页

作者： Ji-heng Li Chao Yuan Xing Mu Xiao-qian Bao Xue-xu Gao State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1 at% Nb C-doped Fe83 Ga17 alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300℃ and 12.0% at 500℃ of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300℃ and 46.6% at 500℃. In the slabs for rolling, the introduction of 〈001〉-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.

关键词： magnetostriction iron-gallium alloys columnar grain ductility abnormal grain growth

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Origins of high ductility exhibited by an extruded magnesium alloy Mg-1.8Zn-0.2Ca:Experiments and crystal plasticity modeling

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Journal of Materials Science & Technology 2021年第25期84卷 27-42页

作者： Jie Wang Gaoming Zhu Leyun Wang Evgenii Vasilev Jun-Sang Park Gang Sha Xiaoqin Zeng Marko Knezevic National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong UniversityShanghai200240China Department of Mechanical Engineering University of New HampshireDurhamNH03824USA Advanced Photon Source Argonne National LaboratoryLemontIL60439USA School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing210094China State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai200240China

Low ductility and strength are major bottlenecks against Mg alloys’wide applications.In this work,we systematically design the composition and fabrication process for a low-alloyed Mg-Zn-Ca alloy,showing that it can be extruded at low temperatures(~250℃)and high speeds(~2 mm/s).After the extrusion,this alloy exhibits a substantially weakened basal texture,relatively small grain size,very high tensile elongation(~30%),and good strength.The origin of the considerably improved ductility was studied using a combination of three-dimensional atom probe tomography(3D-APT),transmission electron microscopy(TEM),electron backscattered diffraction(EBSD)in conjunction with surface slip trace analysis,in-situ synchrotron X-ray diffraction,and elasto-plastic self-consistent(EPSC)modeling.Co-segregation of Zn and Ca atoms at a grain boundary is observed and associated with texture weakening and grain boundary mediated plasticity,both improving the ductility.While basal slip and prismatic slip are identified as the dominant deformation systems in the alloy,the ratio between their slip resistances is substantially reduced relative to pure Mg and most other Mg alloys,significantly contributing to the improved ductility of the alloy.This Mg-Zn-Ca alloy exhibiting excellent mechanical properties and low fabrication cost is a promising candidate for industrial productions.

关键词： Mg-Zn-Ca alloy ductility Deformation mechanisms Crystal plasticity modeling Grain boundary mediated plasticity

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Effect of foundation flexibility on ductility reduction factors for R/C stack-like structures

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Earthquake Engineering and Engineering Vibration 2011年第2期10卷 277-290页

作者： Amir M.Halabian Shabnam Kabiri Faculty of Civil Engineering Isfahan University of Technology

The most important parameter used to determine force reduction factors in force-based design procedures adopted in the current seismic codes is the structural ductility. For a structure supported on a flexible foundation, the ductility factor could be affected by foundation compliances. The ductility factors given in the current codes are mostly assigned ignoring the effect of SSI and therefore the objective of this research is to assess the significance of SSI phenomenon on ductility factors of stack-like structures. The deformed configuration of stack-fike structures is idealized as an assemblage of beam elements considering nonlinear moment-curvature relations, while a linear sway-rocking model was implemented to model the supporting soil. Using a set of artificial records, repeated linear and nonlinear analyses were performed by gradually increasing the intensity of acceleration to a level where the first yielding of steel in linear and nonlinear analyses is observed and a level corresponding to the stack collapse in the nonlinear analysis. The difference between inelastic and elastic resistance in terms of displacement ductility factors has been quantified. The results indicate that foundation flexibility can decrease the ductility of the system and neglecting this phenomenon may lead to erroneous conclusions in the prediction of the seismic performance of flexibly-supported R/C stack-like structures.

关键词： soil-structure interaction R/C stack-like structures ductility

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Enhancement of strength-ductility balance of heavy Ti and Al alloyed FeCoNiCr high-entropy alloys via boron doping

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Journal of Materials Science & Technology 2021年第16期75卷 154-163页

作者： Yongliang Qi Tinghui Cao Hongxiang Zong Yake Wu Lin He Xiangdong Ding Feng Jiang Shenbao Jin Gang Sha Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'anShanxi 710049China School of Materials Science and Engineering Nanjing University of Science and TechnologyJiangsu210094China

As one of the most effective mechanisms,precipitation-hardening is widely used to strengthen high-entropy alloys.Yet,heavy precipitation-hardened high-entropy alloys usually exhibit serious embrittlement.How to effectively achieve ultra-high strength and maintain reliable ductility remains a challenge.Here,we report a study of doping extremely little boron to meet this target.We found that adding of 30 ppm boron into the heavy Ti and Al alloyed FCC FeCoNiCr high-entropy,(FeCoNiCr)_(88) Ti_(6) Al_(6) HEA(at.%)which is strengthened mainly by both coarse BCC-based(Ni,Co)_(2) TiAl Heusler and fine L12-type FCC-based(Ni,Co)_(3) TiAl precipitates and shows ultrahigh strength but poor ductility,could significantly change the original microstructure and consequently improve mechanical performance,owing to the well-known effect of boron on reducing the energy of grain boundaries.The boron addition can(1)eliminate microcavities formed at Heusler precipitate-matrix interfaces;(2)suppress the formation and segregation of coarse BCC Heusler precipitates;(3)promote the formation of L12 nanoparticles.This changes of microstructure substantially improve the tensile ductility more than by~86%and retain comparable or even better ultimate tensile strength.These findings may provide a simple and costless solution to produce heavy precipitation-strengthened HEAs with ultrahigh strength and prevent accidental brittleness.

关键词： High-entropy alloy Precipitation strengthening Boron ductility

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Strategies for improving ductility of ordered intermetallics

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Progress in Natural Science:Materials International 2016年第1期26卷 1-12页

作者： Z.B.Jiao J.H.Luan C.T.Liu Center for Advanced Structural Materials Department of Mechanical and Biomedical Engineering College of Science and Engineering City University of Hong Kong

Ordered intermetallics possess attractive high-temperature properties; however, low ductility and brittle fracture limit their use as engineering materials in many cases. This paper provides a comprehensive review on the recent progress in the development of ductile ordered intermetallics and summarizes the strategies used to improve the tensile ductility of ordered intermetallics, including control of ordered crystal structures,engineering grain-boundary structure and chemistry, eliminating environmental embrittlement, microstructure optimization, control of phase stability, and promoting transformation-/twining-induced plasticity. The basic ideas and related mechanisms underlying these ductilizing strategies are discussed. In addition, a brief mention of the current use of intermetallic alloys for structural and corrosion applications is made.

关键词： Ordered intermetallics ductility Ductilizing strategy Microstructure Alloy design

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Effect of volume fraction and mechanical stability of austenite on ductility of medium Mn steel

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Journal of Iron and Steel Research(International) 2019年第11期26卷 1209-1218页

作者： Si-lian Che Zhao-xi Cao Chang Wang Chong-xiang Huang Dirk Ponge Wen-quan Cao Central Iron and Steel Research Institute(CISRI) Beijing 100081China Science Faculty University of SydneySydney NSW 2006Australia School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065SichuanChina Max-Planck-Institute for Iron Research Duesseldorf 40237Germany

A hot-rolled medium Mn(0.2C5Mn)steel is annealed at 650℃ to produce an ultrafine-grained duplex microstructure with different austenite volume fractions by austenite reverted transformation(ART)annealing,and the orientation relationship strictly obeys K-S orientation relationship before deformation.Tensile tests are carried out in a temperature range from-196 to 400℃ to examine the effects of the austenite volume fraction and the deformation temperature on the tensile properties and the austenite stability.Microstructural observations reveal that the metastable austenite gradually transformed into a-martensite,which is controlled by the deformation strain,the temperature and the austenite volume fraction.Both strain hardening behavior and ductility of the studied steel are dependent on austenite volume fraction and deformation temperature significantly.The stress-strain curves of ART-annealed 0.2C5Mn steel assume an S shape and a very large work hardening rate of about 10 GPa is obtained at liquid nitrogen deformation temperature.Based on the experimental data,a quantitative relation is proposed to describe the ductility dependence on both the austenite volume fraction and its mechanical stability.

关键词： TRIP effect ductility Phase transformation Austenite volume fraction Mechanical stability

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Understanding the enhanced ductility of Mg-Gd with Ca and Zn microalloying by slip trace analysis

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Journal of Materials Science & Technology 2021年第36期95卷 20-28页

作者： Jun Zhao Bin Jiang Yuan Yuan Qinghang Wang Ming Yuan Aitao Tang Guangsheng Huang Dingfei Zhang Fusheng Pan State Key Laboratory of Mechanical Transmissions College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China School of Mechanical Engineering Yangzhou UniversityYangzhou 225127China

This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis.The ductility and microstructure of extruded Mg-0.6Gd and Mg-0.6Gd-0.3Ca-0.2Zn(wt%)sheets were investigated.Basal slip was the main deformation mode under investigation.Ca and Zn microalloying increased the frequency of grain boundaries(GBs)with misorientation angles(θs)ductility for Mg-0.6Gd-0.3Ca-0.2Zn sheet.

关键词： Mg-Gd Ca-Zn microalloying Slip trace Cracking ductility

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