Ambient- to Elevated-Temperature Fracture and Fatigue Properties of Mo-Si-B Alloys: Role of Microstructure

نویسندگان

  • J. J. KRUZIC
  • J. H. SCHNEIBEL
چکیده

Ambientto elevated-temperature fracture and fatigue-crack growth results are presented for five MoMo3Si-Mo5SiB2–containing -Mo matrix (17 to 49 vol pct) alloys, which are compared to results for intermetallic-matrix alloys with similar compositions. By increasing the -Mo volume fraction, ductility, or microstructural coarseness, or by using a continuous -Mo matrix, it was found that improved fracture and fatigue properties are achieved by promoting the active toughening mechanisms, specifically crack trapping and crack bridging by the -Mo phase. Crack-initiation fracture toughness values increased from 5 to 12 MPa with increasing -Mo content from 17 to 49 vol pct, and fracture toughness values rose with crack extension, ranging from 8.5 to 21 MPa at ambient temperatures. Fatigue thresholds benefited similarly from more -Mo phase, and the fracture and fatigue resistance was improved for all alloys tested at 1300 °C, the latter effects being attributed to improved ductility of the -Mo phase at elevated temperatures. 1m 1m

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تاریخ انتشار 2005