CREEP OF A NIOBIUM BERYLLIDE, NB2BE17

A niobium beryllide, Nb2Be17, has been prepared by powder-metallurgy techniques and the mechanical properties characterized both at room and elevated temperatures. Microhardness and fracture toughness were measured at room temperature. Hardness and hot-hardness test results indicated that, although the material was brittle at low temperatures, it became plastic at elevated temperatures (>1000-degrees-C). Creep properties of Nb2Be17 were studied at temperatures from 1250 to 1350-degrees-C and applied stresses from 10 to 90 MPa. The stress exponent, determined from stress-change tests, was about 3, and the activation energy, determined from temperature-change tests, was about 575 kJ/mol. The creep of Nb2Be17 at high temperature is apparently controlled by dislocation glide; this proposal was supported by transient creep experiments. Comparisons have been made between the creep properties of Nb2Be17 and other intermetallics.