Papers by Author: Masataka Tokuda

Abstract: The heat treatment effect of a cast shape memory alloy (SMA) from self-propagating high temperature synthesis (SHS) ingot was investigated. The composition of SHS ingot was Ti-50.8at%Ni. DSC and Tensile test specimens were cast by lost-wax process from SHS ingot. The heat treatment conditions were 400°C-60min., 500°C-60min. and 600°C-60min. for DSC and 400°C-60min. and 500°C-60min. for tensile test. Transformation temperatures were measured by differential scanning calorimetry (DSC). Mechanical properties were measured by a tensile test at several temperatures. The effects of heat treatment temperatures were same as a general TiNi wire material.

Abstract: Bulk glassy metal is an alloy with the vitreous amorphous structure. Because of various excellent properties, this material is expected to use as an alternative structural material for several engineering applications very well. Although bulk glassy metal is very little deformed plastically in the room temperature, it shows the huge super-plastic behavior over the high temperature. However, there is not many reports mentioned about the mechanical properties of bulk glassy metal after plastic deformation under high temperature condition. From the above point of view, in this study, we have investigated the lower bound of temperature at which Zr55Cu30Al10Ni5 bulk glassy metal can be plastically deformed in uniaxial tensile load. Furthermore, it is focused on the strength property of bulk glassy metal in the room temperature after deformed under various high-temperature conditions. In the experimental result, when this material was heated at temperature of 685[K] or higher, this material crystallized and the mechanical strength in room temperature drastically decreased to 200[MPa], although this material as cast had the strength over 1500[MPa]. However, this material showed sufficiently the plastic deformation at temperatures of 643[K] and the strength in room temperature after cooling was equal to as cast. It is supposed that the strength depend on its atomic structure, i.e., amorphous or crystalline, and the change of its structure is affected strongly by heating process.