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Preparation and Characterization of Ultrafine ZrO_ Powders from Solvent Extraction of Zr(Ⅳ) with Tri-n-butyl Phosphate in Kerosene from Nitric Acid Solutions

Chuanfang YANG and Jiayong CHEN (Institute of Chemical Metallurgy , Chinese Academy of Sciences , Beijing 100080 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

Zr(IV) was extracted by tri-n-butyl phosphate in kerosene from concentrated nitric acid solutions and the formation of the third phase during extraction was experimentally investigated. Zirconia powders were prepared by using the loaded organic phase as the bulk solution precipitated with aqueous ammonia or NaOH solution. The powder prepared was characterized with TEM, XRD,EDAX and TG-DTA. Effects of some conditions on powder preparation were studied and it was shown that nanosized particles could be obtained from this extraction system but conditions should be carefully controlled for powder purity and particle size.

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Microstructure and Fracture Morphology in the Welding Zone of Cr18Mo2 Ferritic Stainless Steel

Yajiang LI , Zengda ZOU and M. Thompson (Dept. of Materials Engineering , Shandong University of Technology , Jinan 250061 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

Microstructure, precipitates and fracture morphology in the weld metal and the heat-affected zone (HAZ) of Cr18Mo2 ferritic stainless steel have been studied by means of metalloscope, SEM,TEM and X-ray diffractometer. Experimental results indicate that crystalline grain coarsening in HAZ is one of the reason resulting in the embrittlement fracture in the welding zone of the ferritic stainless steel. Some precipitates (TiC, TiN and Cr2N) in the steel promote production and development of the brittle cracks. In practical applications. the welding heat input should be as small as possible to prevent embrittlement caused by HAZ grain coarsening.

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A Fractal Study on Brittle-Ductile Transition for Ti-24Al-11Nb Alloy

Guoliang CHEN , Yandong WANG , Yuanding HUANG , Zuqing SUNand Wangyue YANG(State Key Lab. for Adv. Met , Mater. , University of Science and Technology Beijing , Beijing , Beijing , 100083 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

The mechanical behaviours of Ti-24Al-11Nb alloy in the brittle-ductile transition (BOT) have been investigated by using three-point bending tests. The temperature dependence of the fractal dimensions and fractal characterization of fracture surfaces are presented. The probable mechanism controlling BDT of intermetallic alloys are proposed according to fractal geometry.Additionally. it is found that there is a positive relationship between the fractal dimension and fracture toughness in BDT for Ti-24Al-11Nb alloy

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Investigation of Truc Ni~(2+)-Halide Distances in Alkali Halide Lattices

Xuanrong MA(Department of Physics , Ningxia University , Yinchuan , 750021 , China)Maolu DU(Institute of Solid State Physics , Sichuan Normal University , Chengdu , 610066 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

Using the μKα model of Ni2+-6X- cluster, the true distances between impurity Ni2+ cation and halide anion in alkali halide lattices are estimated from the optical spectra data. The results suggest that the true impurity cation- ligand anion distances are close to the sum of ionic radii of the impurity cation and ligand anion but not the cation - anion distance of the perfect lattices in the case of that the ionic radius of host cation is more larger than that of impurity cation

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Microstructure and Mechanical Properties of a Duplex Martensite Austenitic Steel Precipitation-hardened by VC Carbide

Changsheng XIE , Jiansheng ZHAO , Peizhen SUN , and Xia LIANG (Dept.of Mech. Eng. Ⅱ , Huazhong University of Science and Technology , Wuhan , 430074 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

This paper presents an investigation on the primary microstructure and mechanical properties of a martensite-austenitic duplex steel precipitation-hardened by VC carbide. The results show that the mechanical properties at room temperature are strongly dependent upon the volume fraction of austenite fA. When fA < 32 % both ultimate strength and Vield strength are decreased with increasing fA. however. whenfA>32%, with increasing the.fA. ultimate strength rises and yield strength drops down. Experimental results at elevated temperatures. show that when test temperature ≤500℃. the yield strength to modulus ratio remains unchanged, however. as the temperature rises a substantial fall in the ratio occurs. The strength values at 600 and 700℃ are increased with increasing strain rate measured by cross-head speed of testing rnachine, The law of mixtures and the contribution of strain-induced transformation from unstable austen ite to martensite to the mechanical properties are discussed.

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Growth Kinetics of γ′ Particles in Incoloy 907

Xu ZHAO , Dongfa LI , Ke YANG , Cungan FAN and Yiyi LI (Institute of Metal Research , Academia Sinica , Shenyang , 110015 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

The kinetics of growth of the γ' precipitate in an lncoloy 907 alloy have been studied. The kinetics of particle growth obeyed the tirne law predicted by the Lifshitz-Wagner theory. The distribution of γ'particle sizes was found to be significantly broader than the theoretical distribution of LifshitZ-Wagner theory. It is suggested that this is due to the relatively large lattice parameter mismatch between γ' and the Fe-Ni-Co matrix

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Microstructure of the Ductile Phase in Intermetallic Compound Ni_(50)Al_(20)Fe_(30)

Lianlong HE , Shuhe WANG , Jianting GUO , and Hengqiang YE (Lab. of Atomic Imaging of Solids , Institute of Metal Research , Academia Sinica , Shenyang , 110015 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

The microstructure of the single hot extruded and annealed Ni50Al20Fe30Y0.003 intermetallic compound alloys has been examined by means of high resolution electron microscopy (HREM). In these extruded and annealed alloys. the ductile phase is of a mixture of the disordered fcc γ matrix and or dered γ' precipitates. This fact well interprets the reason why the degree of annealing treatment can influence the strength and ductility of these alloys. The HREM observation revealed directly that there was some strain concentration at γ'-γ interfaces, due to the presence of more iron atoms in these two phases. The fixed orientation relationship between the γ phase and γ' precipitates was identified to be {001}γ{00 }γ' and <100 >γ < 100 > γ'

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Comparison of K_(IC) Values for SiC Whisker Reinforced Ceramic Composites Obtained by Using Various Methods

Tingquan LEI , Guangyong LIN , Shuangxi WANG , and Yu ZHOU (Dept. of Metals and Technology , Harbin Institute of Technology , Harbin , 150001 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.

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γ-Fe Nano-particles from Fe(CO)_5 by CW CO_2 Laser-driven

Xinqing ZHAO , Yong LIANG , Keshen XIAO , Feng ZHENG and Zhuangqi HU (State Key Lab. of RSA , Institute of Metal Research , Academia Sinica , Shenyang , 110015 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

γ-Fe nano-particles with size of 20-40 nm were produced by SF6-sensitized CW CO2 laser-induced gaseous pyrolysis of Fe(Co) 5, The γ-Fe stabte in reaction zone at above 910℃ was formed.The rapid quenching prevents from the γ-Fe transforming to α-Fe as rapidly cooling from high temperature to room temperature, The characteristics of the particles were examined at room temperature by TEM. electron diffraction and XRD. It was proved that about 70% of γ-Fe phase in the particles was present. In addition. the lattice constant of the γ-Fe was 0.364 nm in place of 0.360 nm

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Crystal Structure during Film Formation

Guoping DU , Hui SHEN , Lanping YUE , Weiguo YAO , Zongquan LI and Zhenzhong QI (Institute of Solid State Physics , Academia Sinica , Hefei , 230031 , China)(To whom correspondence should be addressed)

材料科学技术（英文）

For evaporation-deposited Ti films, face-centred cubic structure was observed at the initial stage of film growth, then transited to the hexagonal close-packed structure during film growing (less than 50 nm thick). While. for ion-beam sputter-deposited films. the structure of films always kept the fcc structure during all stages of film formation. The structure of film at initial growth stages relates with the substrate. It is discussed that different film processes and different growth stages provide different thermodynamic condition of film formation and result in the different crystal structures of films during the film formation

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