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Transformation behavior of precipitates during artificial aging at 170℃in Al-Mg-Si-Cu alloys with and without Zn addition

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Rare Metals 2021年第7期40卷 1907-1914页

作者： Shang Zhu Zhi-Hui li li-zhen yan Xi-Wu li Shu-Hui Huang Hong-Wei yan Yong-An Zhang Bai-Qing Xiong State Key Laboratory of Nonferrous Metals and Processes GRIMAT Engineering Institute Co..LtdBeijing 101407China

The transformation behavior of precipitates in Al-Mg-Si-Cu alloys with and without Zn addition during artificial aging at 170℃was investigated in this *** Al-Mg-Si-Cu alloys with and without Zn addition,two types of precipitates,needle-likeβ″and lath-like L,are formed with the aging time increasing from 8 to 34 *** needle-likeβ″precipitate exhibits a Mg-to-Si atomic ratio of 1.31 which is in agreement with the theoretical ratio of1.25 forβ″(Mg5 Al2 Si4).In addition,theβ″precipitate is supposed to contain Al and *** further partitioning of Mg,Si and Cu and release of Al,the needle-likeβ″precipitate can transform to lath-like L *** L phase has significantly higher concentrations of Mg,Si and Cu and lower concentration of Al,with a higher Mg-to-Si atomic ratio(1.41)deviated from theoretical ratio ofβ″.However,the major of Zn has a random distribution in Al matrix and exhibits no significant partitioning into *** remained in matrix can enhance the transformation ofβ″precipitates to L precipitates.

关键词： Al-Mg-Si-Cu alloys Zn addition Precipitates Transformation

Aging precipitation characteristics and tensile properties of Al-Zn-Mg-Cu alloys with different additional Zn contents

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Rare Metals 2021年第8期40卷 2160-2166页

作者： Kai Wen Bai-Qing Xiong Yong-An Zhang Xi-Wu li Zhi-Hui li li-zhen yan Hong-Wei yan Hong-Wei liu State Key Laboratory of Nonferrous Metals and Processes GRIMAT Engineering Institute Co.LTD.Beijing101407China GRINM Group Co. LTD.Beijing100088China

The increase in zinc content in Al-Zn-Mg-Cu alloys provides an effective method to enhance the *** electron microscopy(TEM)and tensile test were employed to analyze the microstructure and tensile properties,respectively,of Al-9.3 Zn-2.0 Mg-1.8 Cu alloy(9.3 Zn alloy)and Al-9.8 Zn-2.0 Mg-1.8 Cu alloy(9.8 Zn alloy)with single-and double-stage aging *** results showed that the two alloys possessed a closed strength under single-stage peak-aging *** for double-stage aging treatment,9.8 Zn alloy had a higher strength values than 9.3 Zn alloy under the same aging *** the second step aging time prolonging,the strength gap was *** main precipitates for the two alloys with single-stage peak-aging state were GP zones andη’phase,while there were a majority ofη’phases andηphases for the two alloys under typical double-stage over-aging *** double-stage overaging state,the proportion of precipitate with large size for9.3 Zn alloy was larger than that for 9.8 Zn ***,a more obvious trend was revealed for the double-stage overaging *** gap of strength between the two alloys was explained by the difference of precipitation characteristics via interaction mechanism between precipitates and dislocations.

关键词： Zn content Al-Zn-Mg-Cu alloy Precipitation characteristics Tensile properties

Fatigue crack growth behavior of 2624-T39 aluminum alloy with different grain sizes

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Rare Metals 2021年第9期40卷 2523-2529页

作者： Guan Huang Zhi-Hui li li-Ming Sun Xi-Wu li Kai Wen li-zhen yan Bai-Qing Xiong Yong-An Zhang State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co.Ltd.Beijing 100088China GRIMAT Engineering Institute Co. Ltd.Beijing 101407China General Research Institute for Nonferrous Metals Beijing 100088China Northeast light Alloy Co. Ltd.Harbin 150060China

The microstructure of 2624-T39 aluminum alloy was analyzed by means of metallographic(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM). The effects of different microstructure characteristics on the tensile properties and fatigue crack growth rate of 2624-T39 aluminum alloy were *** showed that the grain size of the alloy was a typical fiber structure along the rolling direction, and the main second phase was the A_(l2)CuMg phase. The grain size of the alloy had an obvious influence on the fatigue crack growth rate, and the alloy showed a lower fatigue crack growth rate due to the larger grain size. The crack initiation zone on the fracture surface of alloys with lower fatigue crack growth rate was relatively rough, the crack propagation zone had obvious fatigue striations, and the transient fracture zone had a large number of smaller dimples.

关键词： 2624-T39 aluminum alloy Grain size Fatigue crack growth rate Fatigue fracture morphology

Effect of the Addition of High li Concentration on the Microstructure and Mechanical Properties of Al-Mg-Si Alloys with Different Mg Contents

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1721-1733页

作者： Xiao-Kun yang Bai-Qing Xiong Xi-Wu li li-zhen yan Zhi-Hui li Yong-An Zhang Ya-Nan li Kai Wen State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co.LtdBeijing 100088China GRIMAT Engineering Institute Co. LTDBeijing 101407China General Research Institute for Nonferrous Metals Beijing 100088China

In the present work,the microstructural characteristics and mechanical properties of Al-1.5 Mg-0.6Si and Al-3.0 Mg-0.6Si alloy containing 3 wt%li were investigated by optical microscopy(OM),X-ray diffraction analysis(XRD),scanning electron microscopy(SEM),time of flight-secondary ion mass spectrometry(SIMS),transmission electron microscopy(TEM),and mechanical performance *** addition of li reduces the density of the base alloy by up to 8.4%.The residual second phases contain Mg and Si in the hot-rolled condition,but the Mg/Si atomic ratio decreases after quenching,which means that li substitute some of the Mg and convert Mg_(2)Si into a(Mg,li)_(2)Si phase during solution *** results of SIMS observations confirm *** high Mg-containing alloy has a more rapid hardening response compared to the low Mg-containing *** observation reveals that theδ′-Al3li+β′′-Mg_(2)Si dual phases can be observed in the high Mg-containing alloy after aging for 100 h at 170°*** higher Mg content enhances the precipitation of theδ′phase,which results in the high Mg-containing alloy having a larger average diameter size ofδ′particles and widerδ′-precipitate-free zones(δ′-PFZs).The mechanical properties are significantly improved with the elastic modulus increasing by more than 16.5%.However,the existence of large second phases and wideδ′-PFZs in li-containing alloys is detrimental to their ductility;as a result,their elongation is much lower than that of the base alloy.

关键词： Al-Mg-Si alloy li addition Microstructure Aging behavior Mechanical properties Secondary ion mass spectrometer

Deep drawing of 6A16 aluminum alloy for automobile body with various blank-holder forces

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Rare Metals 2019年第10期38卷 946-953页

作者： Zhao-yang liu Bai-Qing Xiong Xi-Wu li li-zhen yan Zhi-Hui li Yong-An Zhang Hong-Wei liu State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous Metals

Based on the ABAQUS/explicit finite element method,the deep drawing of 6A16 alloy pre-aged and then storaged at room temperature for 1 week with various blank-holder forces(10,14,18 kN) was *** distribution and variation of stress and strain in deformation zones were investigated to drive the forming property and process of the ***,the simulation result was verified combined with the deep drawing *** results show that the stress and strain of the deformation zone have an incremental trend with the blank-holder force increasing while the deformation degree and grain size within a certain deformation zone have an obvious increase and an enlargement,*** the deep drawing,the hardness of products also increases with the enhancement of blank-holder *** blank-holder force of 18 kN is certified as the preferential one by the analysis of microstructure and simulation results.

关键词： ABAQUS 6A16 aluminum alloy Deep drawing test Blank-holder force

Mechanical properties,microstructure and surface quality of Al-1.2Mg-0.6Si-0.2Cu alloy after solution heat treatment

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Rare Metals 2017年第7期36卷 550-555页

作者： li-zhen yan Yong-An Zhang Bai-Qing Xiong Xi-Wu li Zhi-Hui li Hong-Wei liu Shu-Hui Huang Gang Zhao State Key Laboratory for Nonferrous Metals and Processes General Research Institute for Nonferrous Metals Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) Northeastern University

The effect of solution heat treatment （SHT） on mechanical properties, microstructure and surface quality of Al-1.2Mg-0.6Si-0.2Cu-0.6Zn alloy was investigated by tensile test, Erichsen test, surface topography, scanning electron microscope （SEM） and electron back-scattered diffraction （EBSD）. The results indicate that with the increase in SHT temperature, yield strength and cupping test value （IE） of the sheets increase greatly and reach a peak value, then decrease. Meanwhile, intermetallic com- pounds dissolve into matrix gradually. The grains grow up as SHT temperature increases, and abnormal grain growth leads to the surface defects after solution-treated above 560 ~C. Considering mechanical properties, IE value, residual phases, grain size and surface quality of the sheets, SHT temperature for the alloy should not be higher than 550 ℃.

关键词： AI-Mg-Si alloy Solution heat treatment Surface defects Mechanical properties Microstructure

A Multi-Objective Optimal Evolutionary Algorithm Based on Tree-Ranking

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Wuhan University Journal of Natural Sciences 2003年第S1期8卷 207-211页

作者： Shi Chuan, Kang li-shan, li yan, yan zhen-yuState Key Laboratory of Software Engineering, Wuhan University, Wuhan 430072, Hubei,China State Key Laboratory of Software Engineering Wuhan University Wuhan Hubei China

Multi-objective optimal evolutionary algorithms (MOEAs) are a kind of new effective algorithms to solve Multi-objective optimal problem (MOP). Because ranking, a method which is used by most MOEAs to solve MOP, has some shortcoming s, in this paper, we proposed a new method using tree structure to express the relationship of solutions. Experiments prove that the method can reach the Pare-to front, retain the diversity of the population, and use less time.

关键词： multi-objective optimal problem multi-objective optimal evolutionary algorithm Pareto dominance tree structure dynamic space-compressed mutative operator

Effects of supercritical ammonia on bamboo pulping

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Forestry Studies in China 2011年第1期13卷 80-84页

作者： ZHANG Yuan-jing li zhen-qiu SU yan-fang CAO Cheng-yun College of Chemical Engineering Qingdao University of Science and Technology Qingdao 266042 P. R. China

We investigated the effects of supercritical ammonia on pulping of bamboo in a preliminary study,using testers such as differential scanning calorimetry（DSC）,scanning electron microscopy（SEM）,X-ray diffraction（XRD） and energy dispersive spectroscopy（EDS）.The results indicate that under supercritical conditions at 185-190°C,it is possible for the ammonia to realize bamboo *** with conventional kraft pulping,the products can meet the quality requirements of industrial paper.

关键词： supercritical ammonia bamboo pulping

Economists Concern about China's Reform and Revitalization

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China's Foreign Trade 2009年第14期 34-35页

作者： li zhen,Guo yan

The year 2009 is of great historic significance for China which marks the 60th anniversary of this newly emerging nation. Over the past six decades,China's economy has been invariably experiencing reform and revitalization all along its road to prosperity and *** this crucial moment,it is extremely meaningful to look back on what we have already achieved in the past and decide what we must do in the future.

关键词：经济学家电力改革中国历史意义