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Near-microscopic grain boundary facilitates fatigue crack propagation in a polycrystalline Al–Zn–Mg–Cu alloy

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Progress in Natural Science:Materials International 2023年第1期33卷 120-125页

作者： Kai Wen Xiwu Li Baiqing Xiong Haitao Lin Qinghong Wen Yanan Li Hongwei Yan Lizhen Yan Yongan Zhang Zhihui Li Hongwei Liu State Key Laboratory of Nonferrous metals and Processes China GRINM Group Co. LTD. GRIMAT Engineering Institute Co. LTD. General Research Institute for Nonferrous metals Southwest Aluminum(Group) Co. Ltd.

In present study, grain characteristics with sizes within 10–30 μm were fabricated from a same Al–Zn–Mg–Cu alloy, FCP behaviors of the alloys with small grain(SG alloy), medium grain(MG alloy) and large grain(LG alloy)were investigated and related fatigue fracture morphology was analyzed. With the enhancement of stress intensity factor range(ΔK), the alloy with larger grains possessed faster FCP rate, which were successively arranged as SG alloy > MG alloy > LG alloy at initial stage while turned to LG alloy > MG alloy > SG alloy at final stage for the stable expanding region. Except for conventional characteristics of striations, tearing ridges, secondary cracks,second phases, voids and dimples, more prominent grain boundary features appeared on fracture surface, especially for MG and LG alloy. The calculation of cyclic plastic zone(CPZ) sizes proved that grain boundary participated and promoted FCP behavior when CPZ covered grain and grain boundary together.

关键词： Fatigue crack propagation Grain size Grain boundary Cyclic plastic zone Al–Zn–Mg–Cu alloy

Microstructure and tensile properties of magnesium alloy modified by Si/Ca based refiner

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中国有色金属学会会刊：英文版 2005年第4期15卷 878-883页

作者：段志超孙扬善魏宇杜温文薛烽诸天柏 Depart ment of Materials Science and Engineering Southeast University Nanjing Welbow metals Co ltd

Microstructure and mechanical properties of pure magnesium and AZ31 alloy with Ca/Si based refiner addition were investigated. The results indicate that addition of Ca/Si based refiners to pure magnesium and AZ31 alloy results in remarkable microstructure refinement. With proper amount of refiner addition, the grain size in as cast ingots can be one order of magnitude lower than that without refiner addition. Small amount of refiner addition to AZ31 alloy increases both ultimate strength and yield strength significantly,while the ductility of the alloy with refiner addition is similar to that without refiner addition. Addition of refiner improves the deformability of AZ31 alloy and extruded or hot rolled specimens (rods or sheets) with refiner addition exhibit higher surface quality and mechanical properties than those without refiner addition.

关键词：镁合金微结构拉力精炼机

Effect of heat treatment on microstructures and properties of a novel Al-Zn-Mg-Cu alloy for oil drilling

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Progress in Natural Science:Materials International 2019年第2期29卷 217-223页

作者： Yanjun Fu Xiwu Li Kai Wen Shuhui Huang Yang Dong Mao Rao Fubo Yang Yugang Wang Baiqing Xiong Zhihui Li State Key Laboratory of Nonferrous metals and Processes General Research Institute for Nonferrous Metals Shandong Yankuang Light Alloy Co.ltd. Southwest Aluminum (Group) Co.ltd.

In view of the special requirements for strength, heat resistance and corrosion resistance of Al-Zn-Mg-Cu alloy for oil drilling, the Al-6.2 Zn-2.5 Mg-1.6 Cu alloy was prepared by increasing Cu content on basis of Russian Series 1953 alloy. The effect of heat treatment on the microstructures and properties of the alloy was characterized by optical microscope（OM）, scanning electron microscope（SEM） and transmission electron microscope（TEM）, and investigated by tensile test at room temperature, thermal exposure test and corrosion test. The results show that the strength after T6 aging treatment exhibit a decrease trend as an increase of the solution temperature from465 °C to 480 °C. After the solution treated by the rate of 470 °C/1 h, second phases dissolve into the matrix very well and the strength property reaches optimum. The alloy has better comprehensive properties treated by a solution treatment of 470 °C/1 h and then followed by an aging treatment of 120 °C/24 h + 170 °C/1 h + 120 °C/24 h. Under the aging state, the precipitated phases inside the grains are suitable in size, while on the grain boundary distribute discontinuously and the precipitate-free zone is obvious. Besides, the alloy still maintain high tensile properties. The yield strength, tensile strength and elongation are 650 MPa, 686 MPa,12.0%, respectively. The yield strength retention after heat exposure is 92%. The alloy has good corrosion resistance and the exfoliation corrosion degree. The average corrosion rate in the H;S and CO;environment is 0.0024 mm/a, which is far less than the required 0.12 mm/a. It is insensitive to H;S and CO;environments.

关键词： Al-Zn-Mg-Cu alloy Heat treatment Microstructure Mechanical properties Heat resistance Corrosion resistance

Effects of precipitate aging time on the cerium-zirconium composite oxides

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Journal of Rare Earths 2014年第11期32卷 1010-1015页

作者：钟强崔梅生岳梅王琦王磊郭荣贵龙志奇黄小卫 Grirem Advanced Materials Co. Ltd. General Research Institute for Nonferrous Metals

Cerium-zirconium composite oxides with high performance were synthesized by a co-precipitation method, using zirconium oxychloride and rare earth chloride as raw materials. The effects of precipitate aging time on the properties of cerium-zirconium composite oxides were investigated. The prepared cerium-zirconium composite oxides were characterized by X-ray diffraction（XRD）, BET specific surface area, pulsed oxygen chemical adsorption, H2 temperature-programmed-reduction（H2-TPR）, scanning electron microscopy（SEM）, etc. The results showed that the precipitate aging time caused great effects on the properties of cerium zirconium composite oxides. With the increase of aging time, the cerium zirconium composite oxides showed enhanced specific surface area, good thermal stability, and high oxygen storage capacity（OSC）. The best performance sample was obtained while the precipitate aging time up to 48 h, with the specific surface area of 140.7 m2/g, and OSC of 657.24 μmolO2/g for the fresh sample. Even after thermal aged under 1000 oC for 4 h, the aged specific surface area was 41.6 m2/g, moreover with a good OSC of 569.9 μmolO2/g.

关键词： cerium-zirconium composite oxides co-precipitation precipitate aging time thermal stability rare earths

Precious metal-support interaction in automotive exhaust catalysts

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Journal of Rare Earths 2014年第2期32卷 97-107页

作者：郑婷婷何俊俊赵云昆夏文正何洁丽 State-Local Joint Engineer Laboratory of Precious Metal Catalytic Technology and Application Kunming Sino-platinum Metals Catalysts Co. Ltd. State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum metals Kunming Institute of Precious Metals

Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a cartier for active compotmds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature; meanwhile, noble metals can also enhance the redox performance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-sup- port interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction （SMSI） gave a theory support for developing a kind of new cata- lyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals （Pt, Pd, Rh） and support such as A1203, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed.

关键词： strong metal-support interaction automotive exhaust catalyst precious metal Al2O3 CeO2-based oxides rare earths

Aging behavior and fatigue crack propagation of high Zn-containing Al-Zn-Mg-Cu alloys with zinc variation

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Progress in Natural Science:Materials International 2017年第2期27卷 217-227页

作者： Kai Wen Yunqiang Fan Guojun Wang Longbing Jin Xiwu Li Zhihui Li Yongan Zhang Baiqing Xiong State Key Laboratory of Non-ferrous metals and Processes General Research Institute for Nonferrous Metals Northeast Light Alloy Co. Ltd.

In the present work, the influence of two-step aging treatments on hardness, electrical conductivity and mechanical properties of two high Zn-containing Al-Zn-Mg-Cu alloys with zinc content variation was investigated and the detailed T76 aging parameters were proposed. The microstructure of the precipitates were studied by transmission electron microscopy(TEM) and high-resolution transmission electron microscopy(HREM) and then quantitatively investigated with the aid of an image analysis. The fatigue performances were researched by the fatigue crack propagation(FCP) rate test and fracture morphology was observed with scanning electron microscopy(SEM). The results show that the matrix precipitate size distributions of both alloys had significant difference, so as to fatigue crack propagation rates and fracture appearance. The shear and bypass mechanisms of dislocation-precipitate interactions were employed to explain the difference. Among the shearable precipitates, the proportion of larger size precipitates for the higher zinc content alloy is bigger than that for the lower zinc content alloy. The coarse shearable precipitates hinder the propagation of the fatigue cracks, leading to inferior FCP rate. For both alloys, the shear mechanism possesses the dominant factor, finally causing a preponderance in the FCP resistance for the higher zinc content alloy than the lower one.

关键词： Al-Zn-Mg-Cu alloy Fatigue crack propagation Precipitate Aging treatment

Microstructure and properties of Cu-Ni-Si-Zr alloy after thermomechanical treatments

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Rare metals 2013年第2期32卷 144-149页

作者： Xiang-Peng Xiao Bai-Qing Xiong Qiang-Song Wang Guo-Liang Xie Li-Jun Peng Guo-Xing Huang State Key Laboratory for Fabrication and Processing of Non-ferrous metals General Research Institute for Nonferrous Metals Aluminum Corporation of China Limited Luoyang Copper Co. Ltd.

The effect of thermomechanical treatments on the microstructures and properties of Cu-2.1Ni-0.5Si- 0.2Zr alloy was investigated. The hot-rolled plates were solution treated at 920 ℃ for 1.5 h, quenched into water, cold rolled by 70 % reduction in thickness, and then aged at 400, 450 and 500 ℃for various times. The variation in tensile strength and electrical conductivity of the alloy was measured as a function of the aging time. The results show the peak strength value of 665 MPa for the alloy aged at 450 ℃ for 2 h. However, the electrical conductivity is observed to reach a maximum of 47 % IACS aged at 450℃for 8 h. OM, SEM, and TEM were used for microstructural inspection of the alloy. Precipitation occurs preferentially at deformation bands in the cold-rolled alloy. Properties behavior is discussed in the light of microstructural features.

关键词： Cu-Ni-Si-Zr alloy Precipitation Electricalconductivity Tensile strength Microstructural features

A study on comprehensive recycling of waste diamond tools

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Rare metals 2012年第1期31卷 88-91页

作者： Wang, Limin Zhang, Guocheng Ma, Fei General Research Institute for Nonferrous metals Beijing 100088 China General Research Institute for Powder metals Advanced Materials Co. Ltd Beijing 101407 China

This article puts forward a new method of recycling materials in diamond tools comprehensively and efficiently by means of analyzing and summarizing various methods of recycling waste diamond *** the waste diamond tools were decomposed in a mixed acid,metals contained in it went into solution in their ionic forms,while diamond and tungsten carbide particles formed into residues to be *** amounts of metal ions in the leaching solution were adjusted according to the contents of metals in the diamond tools;then,the leaching solution was co-precipitated using oxalic acid as precipitation agent,and ammonia water was added to adjust the pH value of the oxalic *** the right conditions,the comprehensive precipitation rate of metals reached above 98%.Finally,ultrafine pre-alloy powder was obtained by hydrogen reduction of oxalate.

关键词： diamond tools leaching co-precipitation hydrogen reduction

Phase precipitation behavior and tensile property of a Ti-Al-Sn-Zr-Mo-Nb-W-Si titanium alloy

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Rare metals 2018年第12期37卷 1064-1069页

作者： Wen-Jing Zhang Xiao-Yun Song Song-Xiao Hui Wen-Jun Ye Wei-Qi Wang State Key Laboratory for Fabrication and Processing of Nonferrous metals General Research Institute for Nonferrous Metals School of Materials and Metallurgy Northeastern University Baoti Group Co. Ltd.

The characteristic of precipitation behavior of a2 phase and silicide, and the tensile properties at room temperature and 650℃after heat treatments in anovel TiAl-Sn-Zr-Mo-Nb-W-Si titanium alloy（BTi-6431 S） were investigated by microstructure analysis and mechanics performance testing. The results show that no second phase precipitates after solution treatment(980 ℃/2 h, air cooling（AC）). However, when the solution-treated specimens are aged at 600 ℃（600 ℃/2 h,AC）,α;phase precipitates in the primary α phase, and the size of α;phase increases with the aging temperature increasing to 750 ℃. Meanwhile, 50-100-nm S2-type silicide particles precipitate along lamellar phase boundaries of transformed β phase after aging at 750 ℃. BTi-6431 S alloy shows the best650 ℃ ultimate tensile strength（UTS） and yield strength（YS） when treated in solution treatment. However, aging treatment results in a decline in 650 ℃ ultimate tensile strength. This may be attributed to the loss of solution strengthening due to the depletion of Al, Si and Zr of the matrix caused by the precipitation of Ti;Al and（TiZr）;Si;.Silicide is a brittle phase; therefore, its precipitation causes a sharp decrease in the room-temperature ductility of BTi-6431 S alloy.

关键词： High-temperature titanium alloy Precipitation behavior α_2 phase Silicide Tensile properties