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Nucleation mechanisms of dynamic recrystallization in Inconel 625 superalloy deformed with different strain rates

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Rare metals 2012年第3期31卷 215-220页

作者： Guo, Qingmiao Li, Defu Peng, Haijian Guo, Shengli Hu, Jie Du, Peng nonferrous metals Processing Division General Research Institute for Nonferrous Metals Beijing 100088 China

The effects of strain rates on the hot working characteristics and nucleation mechanisms of dynamic recrystallization (DRX) were studied by optical microscopy and electron backscatter diffraction (EBSD) technique. Hot compression tests were conducted using a Gleeble-1500 simulator at a true strain of 0.7 in the temperature range of 1000 to 1150 °C and strain rate range of 0.01 to 10.00 s?1. It is found that the size and volume fraction of the DRX grains in hot-deformed Inconel 625 superalloy firstly decrease and then increase with increasing strain rate. Meanwhile, the nucleation mechanism of DRX is closely related to the deformation strain rate due to the deformation thermal effect. The discontinuous DRX (DDRX) with bulging of original grain boundaries is the primary nucleation mechanism of DRX, while the continuous DRX (CDRX) with progressive subgrain rotation acts as a secondary nucleation mechanism. The twinning formation can activate the nucleation of DRX. The effects of bulging of original grain boundaries and twinning formation are firstly gradually weakened and then strengthened with the increasing strain rate due to the deformation thermal effect. On the contrary, the effect of subgrain rotation is firstly gradually strengthened and then weakened with the increasing strain rate.

关键词： nucleation mechanisms dynamic recrystallization Inconel 625 superalloy deformation strain rate

Microstructure evolution of Al-Zn-Mg-Cu-Zr alloy during hot deformation

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Rare metals 2010年第4期29卷 426-432页

作者： YAN Liangming,SHEN Jian,LI Zhoubing,LI Junpeng,and YAN Xiaodong general research institute for nonferrous metals,Beijing 100088,china general research institute for nonferrous metals Beijing China

Compression tests of the Al-Zn-Mg-Cu-Zr（7055） alloy were performed at various strains and temperatures from 300 to 450℃ under a con- stant strain rate between 10^-2 s^-1and 1 s^-1. Microstructures during hot deformation were studied by transmission electron microscopy （TEM）. Dislocation density, dislocation cells and subgrains of the deformed samples were investigated in detail and compared to make a better understanding of the microstructure evolution. The results showed that stress-strain curves under the experimental conditions belonged to the type of dynamic recovery. When the alloy deformed at various strains and 300℃, the microstructure underwent a process of disordered dislocations to cell structure, subgrain structure and subgrain coarsening. With the temperature increasing, subgrains grew and dislocation density in the interior decreased at a strain rate of 1 s^-1. At the temperature of 350℃, the average diameter of subgrains decreased, sub-boundaries broadened and dislocation density in the interior decreased when the strain rate was increased. The deformed samples of 7055 alloy had smaller subgrains than that of 7005 alloy at the same compression condition because of high alloy content.

关键词： aluminum alloy microstructure evolution dynamic recovery subgrain

Microstructure and thermal conductivity of copper matrix composites reinforced with mixtures of diamond and SiC particles

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Rare metals 2012年第1期31卷 58-63页

作者： Han, Yuanyuan Guo, Hong Yin, Fazhang Zhang, Ximin Chu, Ke Fan, Yeming nonferrous metals Processing Division General Research Institute for Nonferrous Metals Beijing 100088 China

The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this *** effects of the particle volume fraction,the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were *** DEM theoretical calculation results show that,for the diamond hybrid SiC/Cu composite,when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12,the thermal conductivity of the composite can reach 500 W·m-1·*** thermal conduc-tivity of the composite has little change when the particle size is above 200μ*** experimental results show that Ti can improve the wettability of the SiC and *** thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/*** is feasible to predict the thermal conductivity of the composite by DEM theoretical model.

关键词： diamond hybrid SiC/Cu composite microstructure thermal conductivity differential effective medium

Effect of carbide formers on microstructure and thermal conductivity of diamond-Cu composites for heat sink materials

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中国有色金属学会会刊：英文版 2009年第5期19卷 1161-1166页

作者：夏扬宋月清林晨光崔舜方针正 general research institute for nonferrous metals

Diamond-copper composites were prepared by powder metallurgy,in which the diamond particles were pre-coated by magnetic sputtering with copper alloy containing a small amount of carbide forming elements(including B,Cr,Ti,and Si).The influence of the carbide forming element additives on the microstructure and thermal conductivity of diamond composites was *** is found that the composites fabricated with Cu-0.5B coated diamond particles has a relatively higher density and its thermal conductivity approaches 300 W/(m·K).Addition of 0.5%B improves the interfacial bonding and decreases thermal boundary resistance between diamond and Cu,while addition of 1%Cr makes the interfacial layer break away from diamond *** actual interfacial thermal conductivity of the composites with Cu-0.5B alloy coated on diamond is much higher than that of the Cu-1Cr layer,which suggests that the intrinsic thermal conductivity of the interfacial layer is an important factor for improving the thermal conductivity of the diamond composites.

关键词：铜复合材料硬质合金导热系数钻石显微结构散热片金刚石复合材料金刚石颗粒

Effects of microstructure on creep behavior of Mg-5%Zn-2%Al(-2%Y) alloy

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中国有色金属学会会刊：英文版 2008年第3期18卷 580-587页

作者：邹宏辉 general research institute for nonferrous metals

Creep tests of Mg-5%Zn-2%Al(-2%Y) (mass fraction) alloy were carried out at 175 ℃ under the load of 50 MPa, on the cast and solution condition, respectively. Relationship between the creep behavior and microstructure was studied by the optical microscopy, SEM and TEM. The result shows that the primary creep strain is relative to the thermo-stability and the quantity of intermetallic compounds in grain boundary area. During the secondary creep period, the minimum creep rate of solution-treated specimens is substantially decreased as a result of dynamic MgZn2 precipitation.

关键词：镁合金微结构镁-锌相动力沉淀

New method of direct chill casting of Al-6Si-3Cu-Mg semisolid billet by annulus electromagnetic stirring

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Transactions of nonferrous metals Society of china 2010年第9期20卷 1591-1596页

作者：汤孟欧徐骏张志峰白月龙 general research institute for nonferrous metals

The electromagnetic direct chill （EMDC） casting process is a welt-established production route for aluminum alloy ingot, however, the skin effect restricts the casting diameter. In order to avoid this problem, annulus electromagnetic direct chill （A-EMDC） casting process has been developed. A three-dimension finite element computational model of A-EMDC casting process was established by using ANSYS Magnetic-Nodal programs and FLOTRAN CFD programs. Microstruetures of A-EMDC casting semi-solid Al-6Si-3Cu-Mg alloy billets were investigated. Two pairs of vortexes occur within the crystallizer with opposite direction in A-EMDC. The annulus gap is advantageous to increasing circulate flow, reducing the temperature gradient as well as shallowing liquid sump depth. The microstructure obtained by A-EMDC is globular or rosette-like, and the microstructure is homogeneous in the billet.

关键词： electromagnetic stirring semi-solid continuous casting Al-6Si-3Cu-Mg alloy

Tensile and Fracture Properties of 15 vol% SiC_p/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 875-884页

作者： Junhui Nie Jianzhong Fan Shaoming Zhang Shaohua Wei Tao Zuo Zili Ma Zhaobing Xiang general research institute for nonferrous metals

15 vol% silicon carbide particle （SiCp）-reinforced 2009A1 matrix （15 vol% SiCp/2009A1） composites were fabricated by hot isostatic pressing （HIP） and hot extrusion processes. The tensile and fracture properties of 15 vol% SiCp/ 2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength （UTS）, yield strength （YS）, elongation （EL）, reduction in area （RA）, and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus （E）. With the increase of SiCp size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiCp size, and when the SiCp size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.

关键词： Aluminum matrix composites Silicon carbide Tensile properties Facture toughness Particle size

Enhancement of Ti-Cr-V BCC alloys on the dehydrogenation kinetics of Li-Mg-N-H hydrogen storage materials

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Rare metals 2010年第6期29卷 621-624页

作者： WANG Jingchuan,LI Zhinian,LI Hualing,MI Jing,Lü Fang,WANG Shumao,LIU Xiaopeng,and JIANG Lijun general research institute for nonferrous metals,Beijing 100088,china general research institute for nonferrous metals Beijing China

The hydrogen storage properties of a Li-Mg-N-H material doped by a 4 mol.% Ti3Cr3V4 body centre cubic（BCC） alloy hydride and prepared with a ball-milling method were investigated by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and Sievert＇s technology *** results show that the Ti3Cr3V4 BCC alloy hydride/Li-Mg-N-H composite has good reversible hydrogen storage *** dehydrogenation kinetics of the Li-Mg-N-H system can be greatly improved by doping the Ti3Cr3V4 BCC alloy *** composite desorbed 4.1 wt.% hydrogen in the first 60 min at 473 K under 0.1 MPa pressure,but when without the BCC alloy addition,only 3.0 wt.% hydrogen was desorbed under the same dehydrogenation *** can be deduced that the Ti3Cr3V4 BCC alloy uniformly distributed in the Li-Mg-N-H substrate could decrease the activating energy of hydrogen molecules to H atoms and increase H diffusion paths in the composite,enhancing the dehydrogenation kinetics of the Li-Mg-N-H system.

关键词： hydrogen storage alloys hydrogen storage hydrides dehydrogenation

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