Role of Microstructure in Promoting Fracture and Fatigue Resistance in Mo-Si-B Alloys
نویسندگان
چکیده
An investigation of how microstructural features affect the fracture and fatigue properties of a promising class of high temperature Mo-Si-B based alloys is presented. Fracture toughness and fatigue-crack growth properties are measured at 25o and 1300oC for five Mo-Mo3Si-Mo5SiB2 containing alloys produced by powder metallurgy with α-Mo matrices. Results are compared with previous studies on intermetallic-matrix microstructures in alloys with similar compositions. It is found that increasing the α-Mo phase volume fraction (17 – 49%) or ductility (by increasing the temperature) benefits the fracture resistance; in addition, α-Mo matrix materials show significant improvements over intermetallic-matrix alloys. Fatigue thresholds were also increased with increasing α-Mo phase content, until a transition to more ductile fatigue behavior occurred with large amounts of α-Mo phase (49%) and ductility (i.e., at 1300°C). The beneficial role of such microstructural variables are attributed to the promotion of the observed toughening mechanisms of crack trapping and bridging by the relatively ductile α-Mo phase.
منابع مشابه
Ambient- to Elevated-Temperature Fracture and Fatigue Properties of Mo-Si-B Alloys: Role of Microstructure
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 fr...
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