Papers by Author: Takamitsu Shimizu

Abstract: The object in this study is to investigate the pulsating fatigue properties of ferritic and martenstic stainless steels using replica method. The main results obtained in this test are as follows; two kinds of ferrritic stainless steels show the same fatigue strength, even if there is difference in micro-structures due to charge of heat treatment condition. In addition, the fatigue limit of martenstic stainless steel shows higher than that of ferritic one by 230%. It is considered that the static mechanical properties relate to the mean value of micro-structures and the fatigue strength relates to the weakest portion of structures. In addition, the ratio between fatigue limit and hardness number becomes considerably smaller than that of conventional structural steels.

Abstract: Surface amorphization by shot peening in intermetallic compounds was examined. The formation of amorphous layer has been verified in Ti-Ni and Zr-Co-Ni alloys. In Ti-Ni alloy, an amorphous phase and nanocrystalline grains were detected by TEM for 120 s peening duration. However, recrystallization and grain growth occurred, when peening duration was up to 400 s. In Zr-Co-Ni alloy, an amorphous phase coexisting with nanocrystalline grains was observed in Zr-37Co-13Ni alloy. For other alloy compositions (Zr-50Co and Zr-50Ni), an amorphous phase was not observed, and nanocrystalline grains were observed. All the observed nanocrystalline grains may be recrystallized from amorphous phase, because their shape was spherical.