| Project/Area Number |
03650556
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
金属加工(含鋳造)
|
|---|
| Research Institution | HIROSHIMA UNIVERSITY |
|---|
Principal Investigator |
OHMORI Masanobu Hiroshima Univ. Fac. of Eng. Professor, 工学部, 教授 (90034321)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
OKADA Tatsuo Hiroshima Univ, Fac, of Eng. Research Associate, 工学部, 助手 (00233338)
YOSHIDA Fusahito Hiroshima Univ, Fac, of Eng. Associate Professor, 工学部, 助教授 (50016797)
FUKUDA Izumi Yatsushiro Tech, College Associate, 助教授 (80099895)
|
|---|
| Project Period (FY) |
1991 – 1992
|
| Project Status |
Completed (Fiscal Year 1992)
|
| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1992: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1991: ¥1,300,000 (Direct Cost: ¥1,300,000)
|
|---|
| Keywords | Sintered Powder Chromium / Shock Pressure / Decrease in Yield Stress / Ductile-Brittle Transition / Free Dislocations / 延性・ぜい性遷移温度 / 焼結クムロ / 降状応力低下 / 延性ーぜい性遷移温度 |
|---|
| Research Abstract |
The change in the ductile-brittle transition behavior of sintered powder chromium (99.8 mass % purity) explosively shock loaded in water was examined by means of a tension test. The present results can be summarized as follows. (1) The ductile-brittle transition temperature (DBTT) of an as-annealed specimen was found to be 543 and 573 K in tests at strain rates of 1.7X10^<-5> and 1.7X 100^<-4>S^<-1>, respectively. These findings show that the DBTT of the chromium is very sensitive to the deformation speed. (2) Due to the shock loading at 930 and 1420 MPa, the sharp yield observed in the as-annealed specimen was completely eliminated and the yield stress value was considerably decreased. (3) The transition temperature of the specimen shock loaded at 930 and/or 1420 MPa was markedly lower than that of the as-annealed specimen. For example, the DBTT of the specimen treated at 930 MPa was 290 and 403 K in the tension tests at 1.7X10^<-5> and 1.7X10^<-4>s^<-1>, respectively. (4) Deformation twins, a kind of plastic deformation, were not formed in the present chromium subjected to shock pressures up to 1 420 MPa, though they were observed in the steel shock loaded at about 1 000 MPa. (5) The decrease of DBTT in the shock-loaded specimen can be explained in terms of a relationship between the yield stress sigmar and the brittle fracture stress sigmac. Since the yield stress of the chromium is lowered by the shock pressure treatment which induces free dislocations around the elastic discontinuities. such as interfaces between the matrix and the second phases, the condition, sigmar=sigmac, for the occurrence of the ductile-brittle transition is satisfied at a lower tempera-ture in the shock-loaded specimen than in the as-annealed specimen.
|
