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Microstructure and properties of ultrafine WC-co-VC cemented carbides with different co contents

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Rare Metals 2022年第6期41卷 1955-1960页

作者： Kai-HuaShi Ke-Chao Zhou Zhi-You Li Xiu-Qi Zan Kai-Lin Dong Qing Jiang State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Precision Parts Department Zigong Cemented Carbide Corporation LimitedZigong 643011China

Ultrafine WC-co-VC cemented carbides are used extensively in a variety of industrial environments due to their excellent mechanical properties and outstanding wear *** content affects the service performance of the cemented *** the present study,the influ-ences of co content on microstructure,physical,and mechanical properties were investigated *** WC-co-VC cemented carbides with co content varying from 4 wt%and 7 wt%and assistance of VC(0.35 wt%)as inhibitor of WC grain growth were *** physical and mechanical properties were tested and the microstructure characteristics were observed by optical microscope(OM)and scanning electron microscopy(SEM).From the results,it is found that with co content increasing,both the cobalt magnetism and bending strength increase,while the coercive force,Rockwell hardness,density,and abrasive wear resistance *** addition,the OM and SEM results show that the increase of co content in WC-co-VC cemented carbides tends to reduce the quantity and size of micro-pores,and make the fracture mode change from brittle fracture to ductile fracture.

关键词： Ultrafine Cemented carbide co content Microstructure Properties

Thermal expansion behavior of sintered Nd–Fe–B magnets with different co contents and orientations

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Chinese Physics B 2023年第5期32卷 573-579页

作者：孟睿阳徐吉元张家滕刘静方以坤董生智李卫 Division of Functional Material Central Iron&Steel Research InstituteBeijing 100081China

The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and ***, this aspect has not been thoroughly investigated. In this study, three different sintered Nd–Fe–B magnets with varying co content(co = 0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20℃–500℃. It was found that, the coefficient of thermal expansion(CTE) increases with the increase of co contents, while the anisotropy of thermal expansion *** introduction of co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of nonoriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd–Fe–B with controllable CTE.

关键词： thermal expansion sintered Nd–Fe–B magnets orientation co content

Effect of cobalt content on electrochemical performance of La-Mg-Ni system (Ce_2Ni_7-type) electrode alloys

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Journal of Rare Earths 2008年第2期26卷 284-290页

作者：王新林董小平张羊换郭世海吕反修 Department of Functional Material Research Central Iron and Steel Research Institute School of Materials Science and Engineering University of Science and Technology Beijing

In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of co was added in La0.75Mg0.25Ni3.5 alloy. The effect of co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.

关键词： co content Ce2Ni7-type La-Mg-Ni system alloy electrochemical performance rare earths