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Effects of pre-aging on microstructure evolution and deformation mechanisms of hot extruded Mg–6Zn–1Gd–1Er Mg alloys

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Journal of Magnesium and Alloys 2023年第1期11卷 317-328页

作者： Wei Kang Liwei Lu Longbiao Feng Fengchi Lu Chunlei Gan Xiaohui Li School of Materials Science and Engineering Hunan University of Science and TechnologyXiangtan 411201PR China Guangdong Institute of Materials and Processing Guangdong Academy of SciencesGuangzhou 510650PR China School of Mechatronics Engineering and Automation Foshan UniversityFoshan 528000PR China Guangdong Tsing Impulse Science and Technology Co.Ltd. Foshan 528226PR China

The influence of pre-aging treatment on the microstructure,texture and mechanical properties of the Mg–6Zn–1Gd–1Er(wt.%)alloy was *** microstructure analysis shows that the presence of pre-aging is beneficial to{1012}twin nucleation at the early stage of extrusion and inhibits the growth of twins and promotes the formation of[1010]-fiber texture components,thus accelerating the complex process of *** the middle stage of extrusion,the extruded samples under the condition of solid solution were subjected to dynamic precipitation during severe shear *** precipitation of the second phase particles followed the particle stimulating nucleation(PSN)mechanism,which increased the volume fraction of DRX grains during *** the extruded samples under the peak-aged condition,the particles appear dissolved during the severe shear deformation strain,which slows down the DRX *** the later stage of extrusion,the small rod-shaped particles followed the PSN mechanism,and finally formed the strong fiber *** extruded alloy exhibits the strongest mechanical properties under the peak-aged state,with ultimate tensile strength(UTS)of 346 MPa,tensile yield strength(TYS)of 217 MPa,and elongation to failure(EL)of 13.6%.The improvement of mechanical properties is mainly attributed to the existence of strong fiber texture,small rod-shaped and block-shaped phases.

关键词： Mg alloys pre-aging Extrusion Texture Dynamic recrystallization

Effects of Combined pre-straining and pre-aging on Natural aging and Bakehardening Response of an Al-Mg-Si Alloy

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Acta Metallurgica Sinica(English Letters) 2013年第3期26卷 340-344页

作者： Zhiqing ZHANG Huanhuan XU Sainan WU Yin LIU College of Materials Science and Engineering Chongqing University

For a series of Al-0.34／%Mg-1.05／%Si-0.08／%Cu alloys, the effects of pre-treatment on natural aging, bake hardening response and plasticity were investigated using Vickers hardness test and tensile test. Differential scanning calorimetry （DSC） analysis was conducted to reveal corresponding precipitation mechanisms. The results showed that pre-straining and pre-aging alone couldn＇t completely suppress natural aging and improve bake hardening response simultaneously. The sensitivity of the pre-straining and pre-aging on the mechanical properties was evaluated. It was found that pre-aging was the main factor which greatly improved bake hardening response and pre-treatment had a weak influence on plasticity in pre-treated samples. DSC analysis showed that the dissolution trough of clusters disappeared in pre-treated samples, both β”and β＇ precipitation peak shifted to lower temperature and were reduced in pre-strained and pre-aged samples. It was concluded that the formation of Mg/Si clusters was replaced by the accelerated precipitation ofβ” andβ＇ phases, which caused the suppression of natural aging and the improvement of bake hardening response （BHR）.

关键词： pre-aging pre-straining Aluminum alloy Natural aging Bake hardening response Mechanical properties

Improved creep aging response in Al-Cu alloy by applying pre-aging before pre-straining

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Chinese Journal of Aeronautics 2023年第7期36卷 518-530页

作者： Fangpu LYU Chunhui LIU Peipei MA Jianshi YANG Longhui CHEN Lihua ZHAN Minghui HUANG State Key Laboratory of precision Manufacturing for Extreme Service Performance School of Mechanical and Electrical EngineeringCentral South UniversityChangsha 410083China Light Alloy Research Institute Central South UniversityChangsha 410083China Advanced Research Center Central South UniversityChangsha 410083China

The improvement of post-form properties without compromising creep formability has been a critical issue in creep age forming of aluminum alloy component. A pretreatment process incorporating artificial pre-aging at 165 °C for 6 h/12 h/24 h followed by pre-strain(3%–9%)has been developed. This method not only evidently improves the strength but also accelerates the creep deformation during creep aging of an Al-Cu alloy. A strength increase of 50 MPa with a slight decrease of ductility relative to the 9% pre-strained alloy is acquired in the alloy artificially pre-aged for 24 h regardless of the pre-strain level(3%–9%). Artificial aging for 24 h prior to 3%pre-strain enables an increase of creep strain by 30%. The creep strain in the alloy artificially preaged for 24 h and pre-strained by 6% is comparable to that in the alloy pre-strained by 9%. The strength and ductility in the alloy artificially pre-aged for 6 h/12 h and pre-strained by 3% are even slightly higher than those in the alloy purely pre-strained by 9%. The characterizations by transmission electron microscopy reveal that pre-aging at 165 °C could promote the accumulation of dislocations during pre-straining due to the pinning effect of pre-existing Guinier-preston zones(GP zones)/θ’’phases and thus expedite the creep deformation in respect to the pure pre-straining treatment. The enhanced precipitation of θ’phases at these pinned dislocations contributes to the improved strength after creep aging. The results demonstrate applying artificial pre-aging before pre-straining is an efficient strategy to elevate the creep aging response in Al alloys.

关键词： Al-Cu alloy Creep aging pre-aging precipitation pre-strain

Combined effect of pre-aging and Ag/Cu addition on the natural aging and bake hardening in Al-Mg-Si alloys

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Progress in Natural Science:Materials International 2018年第3期28卷 363-370页

作者： Yaoyao Weng Zhihong Jia Lipeng Ding Manping Liu Xiaozhi Wu Qing Liu College of Materials Science and Engineering Chongqing University School of Materials Science and Engineering Jiangsu Province Key Laboratory of Materials TribologyJiangsu University College of Physics Chongqing University

The combined effect of pre-aging and Ag/Cu addition on natural aging and bake hardening in Al-Mg-Si alloys were studied by Vickers microhardness measurement, tensile test, atom probe tomography and transmission electron microscopy. The results showed that Ag and/or Cu addition could further enhance the positive effect of pre-aging on bake hardening for Al-Mg-Si alloys. Although the pre-aged alloys with individual Ag/Cu addition had higher paint bake hardness, the hardness in T4 P temper was relatively high due to effectively forming of Cluster(2) during pre-aging. While the pre-aged Ag-Cu-added alloy had low T4 P temper hardness and higher bake hardening response. The strong interaction energies between Ag/Cu atoms and Mg atoms were responsible for the facilitated clustering and precipitation processes. After paint bake treatment, most of Ag atoms accumulated preferentially at β″/α-Al matrix interface, while Cu atoms entered into the interior of β″resulting in disordered structure within the precipitate.

关键词： Al-Mg-Si alloys Ag addition Cu addition pre-aging Atomic-resolution electron microscopy

Fabrication of Hierarchically Porous FAU/α-Al_(2)O_(3) Monoliths via Gel pre-aging Routes Using Seed Gel as Directing Agent

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China Petroleum Processing & Petrochemical Technology 2020年第4期22卷 46-55页

作者： Wang Jia Jin Qibing Zhao Tianbo College of Information Science and Technology Beijing University of Chemical TechnologyBeijing 100029 Key Laboratory of Cluster Science of Ministry of Education Beijing Institute of TechnologyBeijing102488

Hierarchically porous FAU monoliths were synthesized via the gel pre-aging route using seed gel as directing agent andα-Al2O3 as monolithic *** as-synthesized samples were characterized by means of the Fourier transform infrared spectroscopy(FT-IR),X-ray powder diffraction(XRD),scanning electron microscopy(SEM),and N2 adsorption *** effects of seed gel,gel pre-treatment,and gel pre-aging step were determined,while the possible mechanism for formation of alumina composites via different synthesis processes were *** results showed that the crystal size,the shape,and the loading of the supported FAU could be readily tuned by varying the composition of the crystallization gel without notably changing the structure ofα-*** proposed seed gel pre-treating and gel pre-aging route are simple,reproducible,and practically easy to integrate triple porous structures into large-dimension monoliths,which are proved to be very effective in depositing pure FAU crystals on theα-Al2O3 skeleton surface and strengthening the interfacial interaction between ***,it may provide inspiration to the synthesis of other hierarchical zeolites.

关键词： FAU/α-Al_(2)O_(3)monoliths hierarchical porosity seed gel pre-aging gel pre-treatment

Effect of pre-aging, Over-aging and Re-aging on Exfoliation Corrosion and Electrochemical Corrosion Behavior of Al-Zn-Mg-Cu Alloys

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Journal of Materials Science and Chemical Engineering 2020年第2期8卷 81-88页

作者： Xingzhi Liao Xiaohua Kong Pengxuan Dong Kanghua Chen Science and Technology on High Strength Structural Materials Laboratory Central South University Changsha China Collaborative Innovation Center of Advance Nonferrous Structural Materials and Manufacturing Central South University Changsha China Light Alloy Research Institute Central South University Changsha China

By means of TEM, hardness, conductivity, tensile strength test, fracture toughness test, polarization curve and EIS, the Al-Zn-Mg-Cu alloys treated by a new multi-stage aging system, i.e. pre-aging, over-aging and re-aging (120°C/24h + 160°C/8h + 120°C/24h), were characterized. It is found that compared with the Al-Zn-Mg-Cu alloys treated by T76 (120°C/24h + 160°C/8h), the new multi-stage aging treatment can improve the tensile strength, fracture toughness, hardness and conductivity of the alloys at the same time. This is mainly due to the pre-aging, over-aging and re-aging process of super high strength aluminum alloys. Compared with the two-stage over aging process, the formation of multi-stage multi-phase precipitation structure can improve the strength, toughness and corrosion resistance of the alloys at the same time. The polarization curve is consistent with the conclusion. Therefore, we conducted this study to test how the comprehensive properties of the alloy can be improved.

关键词： Al-Zn-Mg-Cu-Zr Alloys pre-aging Over-aging and Re-aging Exfoliation Corrosion Electrochemical Corrosion

Effect of pre-aging in RRA Treatment on Corrosion Behavior of Spray Formed 7075 Alloy

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Effect of Pre-aging in RRA Treatment on Corrosion Behavior o...

pre-treatment to Improve the Bake-hardening Response in the Naturally Aged Al-Mg-Si Alloy

2016中国有色合金及特种铸造发展论坛

作者： SU Rui-ming QU Ying-dong LI Xiang YANG Dong-sheng YOU Jun-hua LI Rong-de School of Material Science and Engineering Shenyang University of Technology

The effects of pre-aging of RRA treatment on microstructure,mechanical properties,intergranular corrosion(IGC) and exfoliation corrosion(EXCO) behavior of spray formed 7075 aluminum alloy were investigated by transmission electron microscope(TEM),scanning electron microscope(SEM),tensile test,IGC test and EXCO *** results show that the mechanical properties and conductivity of spray formed 7075 alloy could be improved by the under aging as the pre-aging of RRA *** re-aging treatment with the under aging as the pre-aging treatment,lots of tiny dispersive MPt precipitated out again in matrix,the GBP were totally separated and the PFZ were *** tensile strength and yield strength of the alloy are 782 and 726 MPa,respectively,which are higher than that after peak aging treatment or conventional RRA treatment,the IGC and EXCO resistance of the 7075 alloy is excellent with 27.9 μm of corrosion depth and EA of corrosion rating.

关键词： spray forming 7075 aluminum alloy retrogression and re-aging pre-aging corrosion

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Journal of Materials Science & Technology 2011年第3期27卷 205-212页

作者： Chin-Hui Shen Department of Mechanical Engineering Army Academy No.750Longdong Rd.Zhongli CityTaoyuan County 320TaiwanChina

This paper describes pre-treatment methods to improve the bake-hardening response of naturally aged AA6022 （Al-0.6Mg-1.0Si）, which is an alloy used in automotive body panels. These methods are used to accelerate the artificial aging process, which proceeds 30-day period of natural aging. The precipitation behavior of the sheets of this aluminum alloy was analyzed by differential scanning calorimetry （DSC） and electrical conductivity measurements, and subsequently confirmed by microstructure observations by transmission electron microscopy （TEM）. Tensile tests and microhardness measurements were performed to determine the mechanical properties of the samples. Under simulated paint-baking conditions （30 min at 170℃）, the microhardness and the yield strength （YS） of the pre-strained ＋ pre-aged samples were found to be I13 HV and 225 MPa, respectively. These values are considerably higher than those of pre-aged samples, and they did not decrease significantly during the initial stage of artificial aging.

关键词： pre-aging pre-straining Natural aging and Bake hardening

Enhancing the bake-hardening responses of a pre-aged Al-Mg-Si alloy by trace Sn additions

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Journal of Materials Science & Technology 2020年第5期40卷 107-112页

作者： Gang Lu Shuai Nie Jianjun Wang Ying Zhang Tianhai Wu Yujie Liu Chunming Liu Key Laboratory for Anisotropy and Texture of Materials(MoE) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Research Center for Metallic Wires Northeastern UniversityShenyang 110819China Shenyang Industrial Transformation Upgrading Promotion Center Shenyang 110083China

Effects of additions of trace Sn on the bake-hardening responses of a pre-aged Al-0.85 Mg-0.85 Si(in wt%)alloy were investigated through mechanical tests,differential scanning calorimetry,electrical resistivity and transmission electron *** indicate that trace Sn additions reduced the number density of pre-aging clusters by inhibiting the formation of unstable counterpart during pre-aging treatment,leading to low strength and high supersaturation of solute *** a subsequent paint-bake treatment,the presence of highly supersaturated solute atoms and high concentrated free vacancies moderated the activation energy barrier ofβ’’phase and thus kinetically accelerated the formation ofβ’’.Consequently,the trace Sn additions enhanced the bake-hardening responses of the pre-aged alloys *** Sn-containing pre-aged Al-Mg-Si alloys with low strength and great bake-hardening responses hold promising potential for automotive body skin applications.

关键词： Al-Mg-Si alloy pre-aging Trace Sn Bake-hardening responses precipitation kinetics