ZHU Ruihui WANG Yu HAN Qiyong SONG Weixi University of Science and Technology Beijing
,
Beijing
,
China Engineer
,
Institute of Precise and Special New Materials
,
University of Science and Technology Beijing
,
Beijing 100083
,
China
金属学报(英文版)
The dependence of nodularization of graphite upon Ce content in RE bearing nodular cast iron,prepared by directional solidification,has been investigated by electrolytic extraction-radioisotope assay analysis of Ce in each phase of the iron together with measurement of nodulized graphite.Results show that the Ce occurs mainly as alloyed form. In the graphite phase,the Ce content is believed to be characterization of nodularization.The graphite would completely nodulized only the Ce is over a certain content in graphite phase.
关键词:
RE nodular cast iron
,
null
,
null
,
null
Bin GUO
,
Xiaodong XING
,
Huming DAI
,
Ronghua LUO
,
Zhongren WANG
材料科学技术（英文）
A flexible special device for viscous pressure forming is designed and implemented. By using three proportional electro-hydraulic relief valves connected to a computer for precise control of releasing pressure of the medium, we can form differential pressure distribution in the die cavity. With the cooperation of programmable logical controller (PLC), computer and sensor modules in control system the device can satisfy all the requirements of the new forming process.
关键词:
Materials Letters
A new criterion of hardness is proposed based on the analysis of the bonding in fourteen rocksalt-structure solids with the aid of discrete variational Xalpha (DV-Xalpha) cluster calculations. The concept of bond density is introduced to measure the hardness of materials, and there is a good linear relation between bond density and Mohs hardness. Because the calculation does not involve any empirical parameters, it can be conveniently applied to some complicated systems for example, alloys and intermetallic compounds.
关键词:
Science in China Series a-Mathematics Physics Astronomy
In this paper, a new model to describe the dynamic ductile fracture is proposed. The constitutive relation of the elastic-viscoplastic matrix has an overstress form given by previous authors. A dynamic loading surface at constant equivalent strain rate(with the volumetric part also taken into account) is derived and an approximate expression for this dynamic loading surface is suggested. In the case where the porous material element is subjected to spherically symmetric tension, the Carroll-Holt's model and Johnson's model are recovered; and in the case where the strain rate sensitivity of the material tends to zero, the Gurson's model is recovered. Moreover, the normality condition of the plastic strain rate for the dynamic loading surface is discussed, and it is shown that the normality rule is no longer valid in general. Finally, comparisons of this model with the models recently proposed by Pan, Saje and Needleman as well as by Perzyna are also presented.
关键词:
ductile fracture;void growth;rate-sensitive material;solids;localization;fracture
P.Bian
,
Dong-Ying Ju
材料科学技术（英文）
Magnetite (Fe3O4) of ferrite magnetic materials has attracted attentions arising by the chip coil electronic material. However, its industrial applications have been limited by the need of high temperature sintering under reduced pressure or vacuum. In order to develop the process method of low-cost and energy saving with high strength and high magnetism of the magnet, a new low temperature sintering method during CO2 gas and adding small amount of boric acid (H3BO3) are proposed. Here, the superfine magnetite powder was fabricated by decomposition from ferrous oxalate at 500℃ in CO2 gas. The ferrous oxalate was synthesized using iron chloride and ammonium oxalate with the liquid phase precipitation. The magnetite powder compact was produced by Newton press and CIP (cold isostatic press) after adding small amount of boric acid. In this study, the effects of the additive on the mechanical and magnetic properties of the sintered magnet were also evaluated. By characteristic evaluation of the magnet, the validity of the proposed new low-temperature sintering process and the optimal process conditions were confirmed.
关键词:
Ferrite magnet
,
null
,
null
,
null
Ke LU
,
Jian LU
材料科学技术（英文）
In this paper, a concept of surface nanocrystallization (SNC) of metallic materials is introduced. Three types of SNC processes are classified. Different SNC mechanisms and possible techniques for SNC are discussed with emphasis on mechanically induced surface self-nanocrystallization. Further development and prospects are addressed with respect to the properties and behaviors of the materials with a nanocrystalline surface. Enhancement of the behavior of the engineering materials by means of the SNC technology and its industrial application possibilities are analyzed.
关键词:
