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On the deformation behavior of heterogeneous microstructure and its effect on the mechanical properties of die cast AZ91D magnesium alloy

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Journal of Magnesium and Alloys 2022年第7期10卷 1981-1993页

作者： Mengwu Wu Yingying Hou Lin Hua Huijuan Ma Xiaobo Li Shoumei Xiong Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting(HPDC)process,and samples of AZ91D magnesium alloy with different microstructure mainly consisting ofα-Mg grains,β-phase and porosities were obtained.According to the grain orientation analysis,the predominant deformation behavior inα-Mg grains was dislocation slip,supplemented by deformation twinning.Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size ofα-Mg grains in the microstructure was finer and more uniform.During the in situ tensile deformation test,cracks were observed to initiate from gas-shrinkage pore and island-shrinkage,and two main crack propagation mechanisms,porosity growth and coalescence were found accordingly.When the crack was in contact with theβ-phase,it would pass through and fracture the networkβ-phase,whereas bypass the islandβ-phase by detaching it from the surroundingα-Mg grains.Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties,which was the combined effect of matrixα-Mg grains,β-phase,and porosities.

关键词： Magnesium alloy High pressure die casting Microstructure deformation behavior Mechanical properties

Hierarchical structure and deformation behavior of a novel multicomponent β titanium alloy with ultrahigh strength

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Journal of Materials Science & Technology 2022年第12期107卷 227-242页

作者： X.Li X.N.Wang K.Liu G.H.Cao M.B.Li Z.S.Zhu S.J.Wu School of Materials Science and Engineering Beihang UniversityBeijing 100191China Titanium Alloys Laboratory Beijing Institute of Aeronautical MaterialBeijing 100095China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase(αf), nano-scale secondary α phase(αs), and ultrafine FCC substructures can be tailored by solution plus aging(STA) heat treatment. The lateral and epitaxial growth of αfphase promotes the HCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich αfphase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 MPa.In addition, the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy.Therefore, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.

关键词： Titanium alloy Hierarchical structure deformation behavior Ultrahigh strength Elements partitioning

Molecular dynamics simulation and micropillar compression of deformation behavior in iridium single crystals

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Rare Metals 2023年第10期42卷 3510-3517页

作者： Jia-Qi Wu Rui Hu Jie-Ren Yang Bin Gan Gong-Liao Luo Yi Liu Xi-Ming Luo State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metal Sino-platinum Metals Co.Ltd.Kunming Institute of Precious MetalsKunming650106China

The compression behaviors of iridium single crystals with different crystalline orientations were investigated by micropillar compression tests and molecular dynamics(MD) simulations.The results indicated that the deformation process of iridium single crystals with [100]and [110] orientations was presented as the stacking faults expansion and the formation of Lomer-Cottrell locks.And the occurrence of Lomer-Cottrell locks was considered as the interaction of stacking faults on {111} planes by MD simulations.The evolution of crystal structure in compression indicated that the Lomer-Cottrell locks might contribute to the large plastic deformation of iridium single crystals.Moreover,the deformation features in MD simulations showed that the elastic modulus(E) and yield stress(σ_(s)) of iridium single crystals were significantly influenced by the temperature.The elastic modulus and yield stress gradually decreased with an increased temperature for all orientations.Meanwhile,the single crystal with a closely spaced lattice structure exhibited superior mechanical properties at a same temperature.

关键词： Iridium single crystal Crystalline orientation deformation behavior Molecular dynamics Micropillar compression

Health diagnosis of ultrahigh arch dam performance using heterogeneous spatial panel vector model

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Water Science and Engineering 2024年第2期17卷 177-186页

作者： Er-feng Zhao Xin Li Chong-shi Gu The National Key Laboratory of Water Disaster Prevention Hohai UniversityNanjing 210098China NationalEngineering Research Centerof Water Resources Eficient Utilization and Engineering Safety Hohai UniversityNanjing 20098China

Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams.A comprehensive analysis was conducted,focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China.Subsequently,the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored,including periodicity,convergence,and time-effect characteristics.These findings revealed the governing mechanism of main factors.Furthermore,a heterogeneous spatial panel vector model was developed,considering both common factors and specific factors affecting the safety and performance of arch dams.This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions,introducing a specific effect quantity to characterize local deformation differences.Ultimately,the proposed model was applied to the Xiaowan arch dam,accurately quantifying the spatiotemporal heterogeneity of dam performance.Additionally,the spatiotemporal distri-bution characteristics of environmental load effects on different parts of the dam were reasonably interpreted.Validation of the model prediction enhances its credibility,leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam.The findings not only enhance the predictive ability and timely control of ultrahigh arch dams'performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.

关键词： Ultrahigh arch dam Structural performance deformation behavior Diagnosis criterion Panel data model

deformation behavior of Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85Nd Alloy in β/Quasi-β Forging Process

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Journal of Iron and Steel Research(International) 2016年第12期23卷 1297-1302页

作者： Ke-lu WANG Shi-qiang LU Xian-juan DONG Xin LI De-lai OUYANG School of Aeronautical Manufacturing Engineering Nanchang Hangkong University

The hot deformation behavior of Ti 5.6Al-4.8Sn-2.0Zr-1.0Mo 0.35Si 0.85Nd alloy in β/quasi-β forging process was studied using isothermal compression tests over temperature range from 1040℃ to 1 100 ℃ and strain rates form 0. 001 s-1 to 70 s -1. The results show that the flow stress and mierostrueture are sensitive to thermomechanical parameters. The processing maps based on the dynamic materials model at strain of 0.3 and 0.7 were established. The optimum deformation thermomechanical parameters at a strain of 0.7 have two regions that exhibit the peak of power dissipation efficiency. One is the region of 1062-1100 ℃ and 10- 3 10-1.5 s -1 ; and another which represents dynamic recrystallization is 1040-1045 ℃ and 10-1.8 10- 0.5 s -1. The instable region is located where the strain rate is larger than 1 s 1 which corresponds to the mechanical instability.

关键词： titanium alloy β/quasi-β forging deformation behavior processing map process parametersoptim ization

deformation behavior and Microstructure Evolution of Wrought Magnesium Alloys

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Chinese Journal of Mechanical Engineering 2013年第3期26卷 437-447页

作者： WANG Shouren SONG Linghui KANG Sukbong CHO Jaehyung WANG Yingzi School of Mechanical Engineering University of Jinan Korea Institute of Materials Science School of Materials Science and Engineering University of Jinan

There are many researches on the deformation behavior of wrought magnesium alloys, such as AZ31, AZ80, AZ91, and ZK60 magnesium alloys at different temperatures and strain rates, but few of them focuses on the deformation behavior of AZ41M and ZK60M alloys, especially under the twin-roll casting (TRC) state. Meanwhile, the existing researches only focus on the grain refinement law of the magnesium alloys under deformation conditions, the deformation mechanism has not been revealed yet. The hot compression behavior of AZ41M and ZK60M magnesium alloys under the temperature and strain rate ranges of 250-400 ℃ and 0.001-1 s-1 are studied by thermal simulation methods using Gleeble 1500 machine and virtual simulation using finite element analysis software. Simulation results show that sine hyperbolic law is the most suitable flow stress model for wider deformation conditions. The most reasonable selected deformation conditions of ZK60M alloy is 350 oC/0.1 s-1 for TRC and 350 oC/1 s-1 for conventional casting (CC), while AZ41M alloy is 300 oC/0.01 s-1 for TRC and 350 oC/0.1 s-1 for CC. deformation behavior and dynamic recrystallization (DRX) mechanism of them are analyzed at the same deformation conditions. The microstructures of AZ41M and ZK60M alloys are observed at different deformed conditions by optical microscopy (OM) and electron back scatter diffraction (EBSD) and it reveals the flow behavior and deformation mechanism of them. Working harden and work soften contribute to the activation of basal, non-basal slip systems which promote DRX. The proposed research reveals the deformation behavior and mechanism of the AZ41M and ZK 60M magnesium alloys and concludes their optimized deformation parameters and processes and provides a theory basis for their manufacturing and application.

关键词： twin rolling cast deformation behavior dynamic recrystallization hot compression

deformation behavior of Ta wire-reinforced Zr-based bulk metallic glass composites

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Journal of Iron and Steel Research(International) 2018年第6期25卷 601-607页

作者： Sen Chen Hua-meng Fu Zheng-kun Li Long Zhang Hong-wei Zhang Zheng-wang Zhu Hong Li Ai-min Wang Yan-dong Wang Hai-feng zhang School of Materials Science and Engineering NortheasternUniversity Shenyang 110819 Liaoning China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 Liaoning China Dongguan Eontec Co. Ltd. Dongguan 523662 GuangdongChina Liaoning Jinyan Liquid Metal Technology Co. Ltd.Shenyang 110100 Liaoning China

A Ta wire-reinforced Zr-based bulk metallic glass composite with a new type of structure was prepared successfully by the method of liquid metal infiltration. Ta wires distribute uniformly in the metallic glass matrix in the form of spirals. The composite exhibits two yield stages under compressive stress, and the samples are compressed into thin pancakes. The micro-cracks originate at the interface between the Ta wire and the metallic glass matrix and propagate perpendicularly to the interface, which then induce multiple shear bands in the metallic glass matrix due to the stress concentration. Shear cracks form in the metallic glass matrix during the continued loading process as a result of the interaction of shear bands. deformation bands of Ta wires occur under the impact of shear bands. The local stress fields in the composite are changed obviously due to the introduction of the spiral-formed reinforcements. The investigation of the deformation behavior and mechanism suggests a new method for the application of bulk metallic glass composites as the structural materials.

关键词： Bulk metallic glass composite Ta wire Spiral Shear band deformation behavior

deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation

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International Journal of Minerals,Metallurgy and Materials 2010年第1期17卷 46-52页

作者： Liang-ming Yan Jian Shen Jun-peng Li Zhou-bing Li Xiao-dong Yan General Research Institute for Nonferrous Metals Beijing 100088 China

The hot deformation behavior and microstructures of Al-7055 commercial alloy were investigated by axisymmetric hot compres- sion at temperatures ranging from 300℃ to 450℃ and strain rates from 10^-2 to 10 s^-1, respectively. Microstructures of deformed 7055 alloy were investigated by transmission electron microscopy （TEM）. The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation. The hot deformation activation energy of the alloy is 146 kJ/mol. Moreover, the flow stress curves predicted by the modified constitutive equations are reasonably consistent with the experimental results, which confirms that the proposed deformation constitutive equations can provide evidence for the selection of hot forming parameters. TEM results indicate that dy- namic recovery is the main softening mechanism during hot deformation.

关键词： aluminum alloys dynamic recovery hot compression deformation behavior constitutive equation

deformation behavior and creep properties of Co-Al-W-based superalloys:A review

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Progress in Natural Science:Materials International 2021年第5期31卷 641-648页

作者： Yunsong Zhao Yuheng Zhang Yi Zhang Yushi Luo Dingzhong Tang Haitao Liu Huadong Fu Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Institute for Advanced Materials and Technology University of Science and Technology Beijing State Key Laboratory of Rolling and Automation Northeastern University

Co-Al-W-based superalloys may become a next generation of high-temperature structural materials used in the hot-section of gas turbine because of the discovery of γ’-strengthening mechanism. The current understanding of deformation behavior and creep properties of Co-Al-W-based superalloys is reviewed in this study. It is found that the Co-Al-W-based superalloys have strong anomalous yield stress behavior and better creep properties, making it as an attractive candidate for high-temperature structural material. The relationship between deformation/creep microstructure and the properties of the alloys needs to be further clarified, which can provide deeper theoretical guidance for further composition design, optimization of heat treatment processes, and guidance of alloy service.

关键词： Co-Al-W-based superalloys deformation behavior Creep properties