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Formation of ceramic-metal composite layers on die steels by electron beam irradiation

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材料与冶金学报 2015年第2期14卷 152-158页

作者： Takahiro Akao Yuki Sakurai tetsuhiko onda Kazutake Uehara Zhongchun Chen Department of Mechanical and Aerospace Engineering Graduate School of EngineeringTottori University Koyama - minami d - 101 Tottori 680 - 8552 Japan Next Generation Advanced Medical Promotion Center Tottori University Hospital Nishi - cho 36 - 1 Yonago Tottori 683 - 8504 Japan

Surface modifications,which result in formation of a hard layer such as CrN,TiN,TiCN etc. on tool surfaces,have been widely utilized in machining tools. How ever,the hard layer has clear interface with the matrix,thereby the delamination between the hard layer and matrix often occurs because of a mismatch of the thermal expansion coefficients. A composite layer with complicated interfaces between hard material and matrix is desired to avoid such a delamination due to a complicated interface existed between workpiece and coating materials. In this study,the formation of ceramic- metal composite layers on the surfaces of die steels by an electron beam( EB) irradiation technique has been investigated. When WC- Co powder was embrocated onto the substrate surfaces,a composite layer of WC- Co and matrix was formed through solidification after the irradiation-induced melting. The composite layer shows a marble- like texture with WC- rich regions. The hardness of the layer reaches up to 1000 HV. For other ceramic pow ders such as TiN and SiC,only small amount of particles has been incorporated into the composite layer,resulting in a relatively low hardness enhancement after the EB irradiation.

关键词： surface modification die steel composite layer electron beam irradiation

Functionally graded Al_2O_3-ZrO_2 composite prepared by centrifugal slip casting and its mechanical properties

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材料与冶金学报 2006年第4期5卷 296-299页

作者： HAYAKAWA Motozo HARA Yasuyuki LI Xiao-dong onda tetsuhiko Department of Mechanical Engineering Tottofi University Koyama Tottofi 680 - 8552 Japan Graduate student Tottofi University Koyama Tottofi 680 -8552 Japan The Key Laboratory for Anisotropy and Texture of Materials （Ministry of Education） Northeastern University Shenyang 110004 China

Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.

关键词： Al2O3-ZrO2 复合材料离心滑动铸件弯曲强度

Synthesis and characterization of alumina-matrix oxide/oxide composites

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材料与冶金学报 2010年第4期9卷 290-295页

作者： Makoto EZUMI Daisuke NOMOTO Takahiro AKAO tetsuhiko onda Zhong-Chun CHEN Department of Mechanical and Aerespace Engineering Graduate School of Engineering Tottori University Koyama - minami 4 - 101 Tottori 680 - 8552 Japan

Al2O3 matrix oxide/oxide composites containing rod-like Ba-β-Al2O3 and equiaxed ZrO2 particles have been successfully synthesized by an in-situ process from a mixture of Al2O3 and BaZrO3 powders. The long-axis direction of rod-like Ba-β-Al2O3 phase is parallel to [1010], while the longitudinal interface between Ba-β-Al2O3 phase and Al2O3 matrix is parallel to (0001) of the Ba-β-Al2O3 phase. The mechanical properties of the composites, such as Vickers hardness and fracture toughness, are enhanced with increasing the sintering temperature. Furthermore, the presence of rod-like Ba-β-Al2O3 particles results in enhancement of fracture toughness of the in-situ synthesized composites due to crack deflection and crack bridging.

关键词： ceramic matrix composite oxide/oxide composite in-situ synthesis Al2O3 Ba-β-Al2O3

Isothermal and athermal martensitic transformations of ceria cerla doped zilrconian

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材料与冶金学报 2010年第3期9卷 211-216页

作者：音田哲彦原纯平陈中春早川元造日本鸟取大学 Graduate Student of Mechanical and Aerospace Engineering Tottori University Sumitomo Electric Sintered Alloy Ltd.

Martensitic transformation behavior was studied for zirconia containing 4%～10% CeO2 (in mole fraction) by using a dilatometric method. The Ms (Martensite start temperature) decreased near linearly with increasing CeO2. Different transformation modes were observed depending on the composition and cooling rate. ZrO2 containing 6% CeO2 showed isothermal transformation behavior, whereas ZrO2 containing 9% and 10% CeO2 showed athermal transformation behavior. However, ZrO2 containing 8% CeO2 showed either isothermal or athermal transformations behavior depending on the cooling rate. A TTT (Time-Temperature-Transformation) diagram was proposed for ZrO2 containing 8% CeO2.

关键词： martensitic transformation ceria doped zirconia isothermal transformation athermal transformation thermally activated process burst type transformation