1998 Fiscal Year Final Research Report Summary
Athermal Bubble-Strengthening at High Temperatures in P/M Tungsten Fine Wires
| Project/Area Number |
09650766
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Structural/Functional materials
|
|---|
| Research Institution | KYUSHU INSTITUTE OF TECHNOLOGY |
|---|
Principal Investigator |
TANOUE Koji Kyushu Institute of Technology, Department of Materials Science of Technology, Associate Professor, 工学部, 助教授 (80039122)
|
|---|
| Project Period (FY) |
1997 – 1998
|
| Keywords | bubble / interlocking / non-sag grain structure / creep / high temperature / deformation mechanism map / filament / secondary recrystallized grain |
|---|
| Research Abstract |
Scanning electron microscopic (SEM) observation is made to examine the geometry of bubbles in P/H tungsten fine wires after their secondary recrys-tallization is completed. While bubbles, the mean diameter of which is 23 nm, are present at grain boundaries with a high area density of p =10^<13> m^<-2>, the area density of bubbles inside a grain is about 5 % of p . It is also investigated how the morphological change of secondary recrystallized grains grown in tungsten fine wires has an effect on creep at high temperatures after it is quantitatively estimated. The quantitative treatment of the grain morphology is possible by using f1 as the representative one of the grain shape parameters. The optimum interlocked grain structure is defined as the grain morphology in which the grain aspect ratio is minimized under the condition that the area of grain boundaries does not increase drastically. The high-temperature creep can then be characterized by the index DELTA I(=f1-f1^O) which indicat
… More
es the degree of deviation from the optimum interlocking of grains which is designated by f1^0. The region of power law creep in the deformation mechanism maps is minimized at DELTA I=0 at which the grains are most favourably interlocked, being extended as DELTA I deviates from DELTA 1=0. It is considered that the deformation in the region is strongly influenced by grain boundary sliding, being further done by grain boundary cavitation with an increase in DELTA I at DELTA 1>0.
These results have been published in the journals which are listed in another sheet. Many arrays of bubbles existing in wire play an important role in controlling the morphology of secondary recrystallized grains. It was proved that the high-temperature strength is strongly influenced by the grain morphology which is determined by the distribution of bubbles. Accordingly, the athermal bubbles-strengthening is obscured by the change of the grain morphology. It is under consideration how to estimate the net effect of the athermal bubbles-strengthening on the flow stress. Less
|
