5th Metallic Nanostructure Group Seminar
January 12, 2006, 9:00 am
7th floor seminar room, Sengen
Atom probe study of Cu47Zr47Al7Ag7 bulk metallic glass
I. Martin
The development of Cu-based bulk metallic glasses, such as Cu-Zr-Ti, Cu-Hf-Ti, Cu-Ti-Zr-Ni, Cu-Ti-Zr-Ni-Si-Sn, attracted more attention because of their low cost, their high fracture strength (~2GPa) and their relatively high plastic strain compared to other BMG. And finally, Cu-based presented a better glass forming ability than Ni or Ti based alloy. In previous studies, the enhancement of the plasticity of the BMG was related to the presence of crystalline dispersoids in the amorphous matrix, which branch shear bands effectively. So some inhomogeneity in the microstructure is expected from the BMG with high plastic strain. Cu43Zr43Al7Ag7 bulk metallic glass (BMG) presents an unusual high plastic strain which had been explained by the occurrence of phase separation into Ag-rich and Cu-rich amorphous phases. The aim of this study was to investigate the change in the composition after some annealing treatment by 3-dimensional atom probe (3DAP).

Microstructure and mechanical properties of Ti-Zr-Cu-Ni-Be metallic glass
D. Nagahama
Most of Bulk Metallic Glasses (BMGs) reported so far exhibit a plastic strain in the range of 0-3% when deformed under compression mode. This limited plastic strain in monolithic BMGs is usually correlated to their failure along a single shear band. The plastic strain of BMGs can be significantly improved by forming a composite structure composed of nanocrystallites embedded in amorphous matrix. However, recent reports show that the compressive strain of monolithic amorphous Ti-based and Pt-based BMGs can reach up to ~7% and ~ 25%, respectively. Such a high plastic strain is explained by the formation of multiple shear bands. However, the correlation between the microstructure and the multiple shear band formation in the Ti-based and Pt-based BMGs has remained unclear. The purpose of this investigation is to study the correlation between the microstructure and the mechanical properties of Ti-based BMG in the as-cast state and upon annealing.

Characterization of Cu-Zr two phase nanolamellar structures produced by Accumulative roll bonding
S. Ohsaki
Processing fine grained microstructures by severe plastic deformation (SPD) has received much research interest these days as a technique which can improve mechanical properties of metallic materials without addition of alloying elements. Many kinds of metallic materials have been achieved the fine grained microstructures by SPD techniques. Two phase alloy is also substantially deformed by SPD. In addition to it, some unique microstructural features have been reported in the severely deformed two phase alloys and its components, such as dissolution of precipitations, super saturated solid solution and formation of amorphous phase. Accumulative roll-bonding (ARB) is one of the SPD methods, which can produce a bulk sheet with fine grained microstructure by repeating of roll bonding process. It can also apply to synthesize different metallic components by repeating of ARB process, it can produce Nonequilibrium and amorphous phases by mechanical mixing and significantly increasing the number of the layers like mechanical alloying. However, it has never reported the attempt of the synthesizing the bulk metallic components using ARB. In this talk, I will present characterization results and microstructural evolution of Cu-Zr multilayer sample synthesized by ARB process as a bulk mechanical alloying.