Mo-Si-B Alloy Development

the 17th Annual Conference on Fossil Energy Materials

J. H. Schneibel ; Jamie J. Kruzic ; Robert O. Ritchie

Others  :  http://www.netl.doe.gov/publications/proceedings/03/materials/manuscripts/Schneibel_m.pdf
PID  :  49027

来源: CEUR

【 摘 要 】

Mo-Si-B silicides consisting of the phases α-Mo (Mo solid solution), Mo_3 Si, and Mo_5 SiB_2have melting points on the order of 2000°C and have potential as ultra-high temperature structural materials.Mo-Si-B alloys can be processed such thattheα-Moispresentintheformofisolatedparticlesinasilicidematrix,or as a continuousmatrix“cementing” individualsilicideparticlestogether. The latter microstructureissimilartothatofWC-Cohardmetals. Thispaper focuses on the relationship between the topology as well as scale of the microstructure of Mo-Mo_3 Si-Mo_5SiB_2alloys, andtheircreepstrengthandfracturetoughness.For example,the creep strength of Mo-Si-B alloys is improvedby reducing the α-Mo volume fraction and by making the α-Mo phase discontinuous.The fracture toughness is improved by increasing the α-Mo volume fraction and by making the α-Mo phase continuous.Room temperature stress intensity factors as high as 21 MPa m 1/2were obtained.The room temperature fracture toughness of Mo-Si-B alloys can also be improved by microalloying with Zr. The room temperature ductility of Mo itself can be improved by adding MgAl_2O_4 spinel particles suggesting yet another way to improve the ductile phase toughening of Mo-Si-B alloys.