Michihiro Tagami

Effects of grain-boundary configuration on the high-temperature creep strength of cobalt-base L-605 alloys

AbstractThe effects of grain-boundary configuration on the high-temperature creep strength are investigated using commercial cobalt-base L-605 alloys with low carbon content in the temperature range 816 to 1038° C (1500 to 1900° F). Serrated grain boundaries are formed principally by the precipitation of tungsten-rich b c c phase (the same as α2 phase found in Ni-20Cr-20W alloys) on grain boundaries by a relatively simple heat treatment in these alloys. The creep rupture properties are improved by strengthening of grain boundaries by the precipitation of tungsten-rich bcc (α2) phase. The specimens with serrated grain boundaries have longer rupture lives and higher ductility than those with normal straight grain boundaries under low stress and high-temperature creep conditions, while the rupture lives and the creep ductility of both specimens are almost the same under high stresses below 927° C. The matrix of the alloys is strengthened by the precipitation of carbides at temperatures below 927° C and by the precipitation of tungsten-rich α2 phase at 1038° C during creep. It is found that there is an orientation relationship between tungsten-rich a2 phase particles andβ-Co matrix, such that (0 1 1)α2 ¶ (1 1 1)β-Co and [1

Development of Solid Lubricants Dispersed Bronze Bearing Material by P/M (Second Report) : Effects of V Addition on Sinter Densification of Cu-Sn Alloy Compacts

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Interfacial Shear Strength of Aluminum-Ceramic Composites.

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High Ductility of Polycrystalline 70-30 Brass at Intermediate Temperatures

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Effect of Grain Size on High Temperature Deformation of Cu-30 mass%Zn Alloy

0]β-Co. The fracture surface of specimens with serrated grain boundaries is a ductile grain-boundary fracture surface, while typical grain-boundary facets prevailed in specimens with straight grain boundaries.

Phase Diagram Based on Solidification Structure in Fe-25%Cr-C-B Alloys

In the previous paper, we reported the densification of the bronze matrix was promoted by the diffusion of Cr under solid state sintering at 1030 K. In the present work, effects of V addition on sintering properties and microstructures of the bronze matrix were investigated, and compared with Cr. Mixed powders were prepared from pulverized V powders and atomized 90Cu-10Sn powders, of which particle sizes were 106-150μm and 1-38μm respectively. Compacts pressed at 390 MPa were sintered at 670-1030 K for 0.3-180 ks in H2. V diffuses preferentially into the surface and grain boundary of the bronze powder. With increasing sintering time at 1030 K, pores of matrix decrease rapidly. This indicates that the densification of the bronze is promoted by the diffusion of V as same as the case of Cr. However, some pores are observed on the matrix and the grain size is bigger than the case of Cr after 180ks sintering at 1030 K. From these results, it is assumed the effects of densification by V addition is slightly smaller than Cr.