2004 Fiscal Year Final Research Report Summary
PRODUCTION OF HIGH FRACTURE TOUGHNESS AND HIGH FATIGUE STRENGTH BULK METALLIC GLASSES AND EXAMINATION OF THE MECHANISM
| Project/Area Number |
14350063
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Ube National College of Technology |
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Principal Investigator |
FUJITA Kazutaka Ube National College of Technology, Mechanical Eng., Prof., 機械工学科, 教授 (10156862)
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| Co-Investigator(Kenkyū-buntansha) |
HATANAKA Kenji Ube National College of Technology, Principal, 校長 (60026193)
KUBUKI Shiro Ube National College of Technology, Chemical and Biological Eng., Associate Prof., 物質工学科, 助教授 (90321489)
YAMAZAKI Tohru University of hyogo, Mater. Sci. and Chemistry, Associate Prof., 工学部, 助教授 (30137252)
YOKOHAMA Yoshihiko Tohoku Univ., Institute of Materials Research, Associate Prof., 金属材料研究所, 助教授 (00261511)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Bulk Metallic Glass / Amorphous / Microcrystal / Nanocrystal / Fracture toughness / Fatigue / Tensile strength / Plastic strain |
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| Research Abstract |
Single phase (SF) bulk glassy alloys (BGAs) and nanocrystalline (NC) EGAs of some Zr-, Cu- and Pd-based systems have been synthesized by some fabrication methods. Where, the NC BGA is the glassy alloy which contain nano-scale crystalline particles embedded homogeneously in glassy matrix. Then fatigue strength and fracture toughness in these BGAs were examined.
The ratio of fatigue limit (σ_w ; half a full stress amplitude) under stress ratio of 0.1 to tensile strength (σ_B) of the Zr-based NC BGA showed a value of 15% (σ_B=1.7 GPa), and it was approximately three times larger compared with the ratio of the SF BGA of the same composition. The ratio of σ_w to σ_B of the Cu-based BGA exhibited a very large value of 24% (σ_B=2.0 GPa). These σ_w s show the enough values for applications. It is thought that the drastic rise in the σ_w of these NC BGAs is derived from the prevention of slip initiation and propagation by the NC particles.
A Zr-based BGA with a high degree of amorphousness exhibited a fracture touness value (Kic) of 53 MPa・m^<1/2>. It was clarified that the Zr-based BGA has a sufficient Kic for practical uses. The Kic s of a Zr-based NC BGA and considerably crystallized Zr-based BGA were small even in the maximum value with 40 and 11 MPa・m^<1/2>, respectively. This is thought to be due to the embrittlement by the crystallization.
The Pd-based SF BGA could not have fatigue cracks, and the value of notched fracture toughness exhibit 36 MPa・m^<1/2> and cracks propagated in three or more directions at the same time. An estimated K/c showed a small value of 12 MPa・m^<1/2>.
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