Ambient- to elevated-temperature fracture and fatigue properties of Mo-Si-B alloys: Role of microstructure |
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| Authors: | J J Kruzic J H Schneibel R O Ritchie |
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| Affiliation: | (1) the Department of Mechanical Engineering, Oregon State University, 97331 Corvallis, OR;(2) Oak Ridge National Laboratory, Metals and Ceramics Division, 37831 Oak Ridge, TN;(3) the Materials Sciences Division, Lawrence Berkeley National Laboratory, and the Department of Materials Science and Engineering, University of California, 94720 Berkeley, CA |
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| Abstract: | Ambient- to elevated-temperature fracture and fatigue-crack growth results are presented for five Mo-Mo3Si-Mo5SiB2-containing α-Mo matrix (17 to 49 vol pct) alloys, which are compared to results for intermetallic-matrix alloys with similar compositions.
By increasing the α-Mo volume fraction, ductility, or microstructural coarseness, or by using a continuous α-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 α-Mo phase. Crack-initiation fracture toughness values increased from 5 to 12 MPa√m with increasing α-Mo content from 17 to 49 vol pct, and fracture toughness values rose with crack extension, ranging from 8.5 to 21 MPa√m at
ambient temperatures. Fatigue thresholds benefited similarly from more α-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 α-Mo phase at elevated temperatures. |
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