材料期刊网

Preparation, Microstructure and Age Hardening of Rapidly Solidified Mo-alloys

NING Yuantao , S. H. Whang Institute of Precious Metals , Kunming , Yunnan , China. Barnett Institute of Northeastern University , Boston , MA 02115 , U. S. A.

材料科学技术（英文）

Various Mo-base alloys with high melting temperature were processed into ribbons and foils by the arc melt-spinning and the arc melt hammer-anvil technique. The preparation of ribbon and foil was introduced. The mechanical proper- ties, the surface topology and the microstructure of rapidly solidified Mo-base alloys containing B were examined. A strong grain refinement and a strong age-hardening response were observed on the as-quenched and the age specimens, the precipitates which cause age hardening were identified to be Mo_2B in Mo-B alloys, Mo_2B and ZrB_2 in Mo-Zr-B alloys, and Mo_2B and ThB_4 in Mo-Th-B alloys. The results indicate that the high strength Mo-base alloys containing boride precipitates can be developed by rapid solidifica- tion technique.

关键词: Mo-alloys , null , null , null , null

XRD STUDY OF RECOVERY PROCESS OF COLD DEFORMED Ag AND Ag-Ce ALLOY

NING Yuantao , WENFei(Kunming Institute of Precious Metals Kunming 650221.China)Manuscript received 4 May 1995

金属学报(英文版)

The recovery processes of cold deformed Ag and Ag-Ce alloy containing trace cerium were studied by XRD analysis.Based on Scherrer formula and an analytical program,the lattice distortion and subgrain size for both Ag and Ag-Ce alloy were determined in the recovery process.The cold deformed high purity Ag showed tow recrystallization temperature,obvious lattice relaxation and age-softening.The trace Ce solute is an effective inhibitor for recovery softening of high purity Ag since it raises the recrystallization temperature and restrains the lattice relaxation.

关键词: :Ag , null , null , null

Improving the electrochemical properties of natural graphite spheres by coating with a pyrolytic carbon shell

新型炭材料

Two kinds of modified natural graphite (MNG) spheres with a pyrolytic carbon shell on smooth or granular surface were obtained using fluidized bed chemical vapor deposition of acetylene by adjusting the reaction parameters. The core of the NING has a highly ordered graphite structure and the shell has a disordered structure. Compared with natural graphite (NG) spheres, MNG with a core-shell structure shows improved first cycling efficiency and cyclability. Especially, the NING spheres with a granular surface possess 84% retention of the first discharge capacity after 41 cycles, owing to effective decrease of the contact resistance and increase of contact area between the NING spheres.

关键词: fluidized bed chemical vapor deposition;core-shell structure;pyrolytic;carbon;modified natural graphite;lithium ion secondary battery;lithium-ion batteries;chemical-vapor-deposition;1st-cycle charge loss;anode material;encapsulated graphite;surface-area;infiltration;performance;improvement;pyrocarbon

STUDIES ON PRIMARY CRYSTALLIZATION OF RAPIDLY QUENCHED Al-Ni-Cu-Nd METALLIC GLASS BY USING HIGH RESOLUTION TRASMISSION ELECTRON MICROSCOPY

Y.D.Xiao , W.X.Li , D.Jacovkis , M.T.Clavaguera-Mora , J.Rodriguez-Viejo , N.Clavaguera

金属学报(英文版)

Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous rib-bon and the annealed samples were closely examined by means of differential scan-ning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in pri-mary crystallization into α-Al nanocrystalline particles, in order to understand struc-tural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of α-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at 110℃ for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃/min consist of large amount of α-Al fec crystal nanoparticles dispersed uni-formly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crustal is soft impinaement, instead of geometric impinqement.

关键词: rapid solidification , null , null