材料期刊网

Quasicrystalline Phase in As-cast Mg-Zn-Y-Zr Alloy

Yali TANG , Ningfu SHEN and Xin YUAN (Research Center for Materials , Zhengzhou Institute of Technology , Zhengzhou , 450002 , China)Zhiping LUO and Shaoqing ZHANG (Institute of Aeronautical Materials , Beijing , 100095 , China)(To whom correspondence should be ad

材料科学技术（英文）

An icosahedral phase in as-cast Mg 5. 78Zn-0.89Y-0.48Zr (wt-%) alloy has been identified with transmission electron microscope (TPM) The selected area diffraction patterns (SADP) from the phase show a five-fold symmetry of a quasicrystalline structure. The energy dispersive X-ray spectra (EDXS) indicate that the quaternary phase has a chemical composition of 67.6Zn-1 9.4Mg-8,1 Y-4 9Zr in at -%

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Extrusion Deformation Texture of SiC_W/Al Composites

JIAO Chengge YAO Zhongkai HAN Yafang Beijing Institute of Aeronautical Materials , Beijing , 100095 , ChinaHarbin Institute of Technology , Harbin , 150006 , China

材料科学技术（英文）

The interface orientation relationships between SiC whiskers and matrix have been studied by X-ray diffraction and crystallite orientation distri- bution functions (CODFs) analysis.The distribu- tion of SiC whiskers in Al matrix of the as-cast SiC_w/Al composite was nearly unperfect isotropic. Both matrix and SiC whisker in as-extruded SiC_w/Al composite were〈111〉fiber texture.It is suggested that there are certain interface orientation relationships between the SiC_w and the Al matrix.

关键词: texture , null , null

Hydrogen Treatment of Cast Ti-6Al-4V Alloy

ZHANG Shaoqing PAN Feng Institute of Aeronautical Materials , Beijing , 100095 , China.

材料科学技术（英文）

This paper presents the results of an investiga- tion of the effect of hydrogen treatment on microstructures and tensile and low cycle fatigue properties of a Ti-6Al-4V cast alloy.The phase transformation and the refining mechanism of the cast microstructure during the process of hydrogen treatment were studied.It was found that after hydrogen treatment,the coarse Widmansttten structure of the as-cast Ti alloy was transformed into a very fine and equiaxed α+β microstructure without any GBα phase.The tensile strength and ductility and the low cycle fatigue life of the hydrogen treated specimens were significantly im- proved.

关键词: Ti-6Al-4V , null , null , null , null , null

Kinetics of Oxidation Resistance of the Ti_3Al-base Intermetallic Alloys

GUO Chaoqi YANG Bingguang MA Jiming ** Institute of Aeronautical Materials , Beijing , 100095 , China+ To whom correspondence should be addressed

材料科学技术（英文）

关键词: Ti_3Al intermetallic compound , null

A New Dispersion-strengthening Phase in an Aged RST Al-8Fe-2Mo-2Zr-2Nd-0.7Ti-1.6Si Alloy

Shenglong DAI Guifu YU Minggao YAN Institute of Aeronautical Materials , Beijing , 100095 , China

材料科学技术（英文）

An effective dispersion-strengthening phase in Al-8Fe-2Mo-2Zr-2Nd-0.7Ti-1.6Si alloy was identified to be an aged precipitate phase with possible chemical stoichiometry of Al_(20)(Ti,Mo)_2 Nd and fcc crystal structure with a_o=1.455 nm.The structure was determined to be Fm3m space group.

关键词: high temperature Al alloy , null , null

Weakening Mechanisms of Platelike σ Phase on Ni-base Superalloys

LIU Yuesheng ZHAO Xianguo LIU Zhizhong XIE Xishan Beijing Institute of Aeronautical Materials , 100095 , China. University of Science and Technology Beijing , 100083 , China.To whom correspondence should be addressed.

材料科学技术（英文）

On the basis of an investigation on σ phase in Ni-base cast superalloy K24 and the results about σ phase in other Ni-base superalloys,an embrittl- ing mechanism and a softening mechanism,by which platelike σ phase weakens the Ni-base superalloys,have been proposed.It is considered that the platelike morphology and the habit precipi- tation along{111}of σ phase are necessary condi- tions for both mechanisms.The embrittling mecha- nism is dominant at room temperature and high strain rate,and the softening mechanism is domi- nant at high temperature and low strain rate.Ac- cording to the idea of the softening mechanism and the analyses of σ phase and alloy compositions,it is considered that Nb,Mo and W in the alloys may be resistant to the detrimental effect of σ phase on the stress-rupture properties of the alloys.

关键词: Ni-base superalloys , null , null

Nucleation and Formation of Stable and Metastable Phases in Undercooled AI-Li Melts

Shenglong DAI Guifu YU Minggao YAN Institute of Aeronautical Materials , Beijing , 100095 , China

材料科学技术（英文）

A modified nucleation and competitive growth kinetic theory considering unsteady nucleation and effect of composition in dilute binary alloys was suggested,based on which the selections of δ.δ' and α phases in undercooled Al-Li melts were summarized by both isothermal and continuous cool- ing treatment methods.

关键词: undercooling , null , null

Phase Transformation and Deformation Mechanism of Ti_3Al-base Alloy

By WANG Shuncai LI Chunzhi GAO Yang CAO Chunxiao YAN Minggao Institute of Aeronautical Materials , Beijing , 100095 , China.To whom correspondence should be addressed.

材料科学技术（英文）

The phase transformation and deformation mechanism of the alloy based on composition Ti_3Al with addition of Nb,V,Mo have been studied by use of transmission electron microscopy (TEM).It has been shown that the orientation relationship of α_2 phase transformed from β phase is:(0001)α_2// (l10)β,[1210]α_2//[111]β.The present dislocation slip systems in α_2 phase are (1100)[0001] and (1100)<1120>.There also exist α_2 twins which have new twin relationship and the twin plane is (2021).

关键词: Ti_3Al-base alloy , null , null

DirectionaHy Solidified High-strength Superalloy DZ22

CHEN Rongzhang WANG Luobao WANG Yuping ** Institute of Aeronautical Materials , Beijing , 100095 , China+ To whom correspondence should be addressed

材料科学技术（英文）

Alloy DZ22 possesses rather high intermediate and elevated temperature mechanical properties comparable with the advanced commercial DS al- loy PWA1422.The alloy composition is based on PWA1422 alloy,only the content ranges of Hf,C and Zr are changed for systematic study.The pres- ent melting technology for master alloy ingot and DS process parameters for components are suitable for this alloy.The alloy revert which has been specially processed can be reused.The mould with- drawal rate during directional solidification affects the crystal orientation,alloy structure and the me- chanical properties of DS castings.The increment of solution-treatment temperature increases obvi- ously the longitudinal stress-rupture life at high temperature but decreases transversal one at inter- mediate temperature.The production practice in batches has demonstrated that alloy DZ22 has not only high mechanical properties but also excellent processing performance,including castability, weldability and machinability.It is indeed a favorable material for advanced aero and land gas turbine engine blades with complex inner cooling passage.

关键词: directional solidification , null , null , null