Alloying effects on fracture mechanisms in Nb-based intermetallic in-situ composites

The fracture mechanisms in Nb-based intermetallic in-situ composites are reviewed to assess the influence of alloy composition on fracture resistance. The beneficial effect of Ti addition in enhancing the fracture resistance of Nb-based in-situ composites is established and explained on the basis of a reduced Peierls-Nabarro barrier energy, whose reduction leads to increased dislocation mobility and plastic flow in the solid solution phase. Recent modeling efforts to increase the fracture resistance of intermetallic and in-situ composites using computational approaches to identify alloying effects are summarized. One approach that relies on computation methods to design the matrix compositions of the ductile phase for optimum fracture resistance and ductility is highlighted. Extension of this approach to NbCr2, and other intermetallics is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.