Papers by Author: Tamaki Shibayama

Abstract: Copper/aluminum/stainless steel (Cu/Al/STS) clad materials were made by rolling and heat treatment process. These specimens were evaluated the formability and bonding strength of Cu/Al/STS clad materials. Thin disc specimens for TEM observation were prepared from the interfaces of Cu/Al and Al/STS by using the Focused Ion Beam (FIB) utility. Brittle oxide film formed on copper surface during heat treatment at 673K~773K. Diffusion bonding was observed at the interface of Cu/Al. Reacted region was formed in the interface of Al/STS with width about 10nm, while in the case of Cu/Al was formed about 1,600nm width. It was also observed nanosized crevice in reacted region of Al/STS interfaces.

Abstract: The microstructures of oxide scales formed on MoSi2 at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO3 and crystallization of amorphous SiO2 scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO2 with small amounts of fine MoO3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO2. Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO2. It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O2 diffusion to lattice diffusion of O2- through SiO2. In addition, the diffusion coefficient of oxygen was estimated from the growth rate of SiO2 scale.

Abstract: The effect of helium on irradiation damage behavior in Fe-Cr-Mn(W,V) steel was investigated by electron/helium ion dual-beam irradiation. The results indicate that helium can promote the increase of dislocation density and enhance the void nucleation and void swelling of Fe-Cr-Mn(W、V) alloy. The segregation of solute elements near grain boundary was suppressed by existence of helium. Also the interface of carbide-matrix migration and the change of solute concentration near the interface were observed during dual-beam irradiation.