A 95wt%W 3.5wt%Ni 1.5wt%Fe alloy is strained to failure in uniaxial tension at temperatures in the range -100 degrees C to 300 degrees C. The fracture surfaces of the tensile specimens are examined and the contributions from the fracture mechanisms: tungsten-tungsten intergranular decohesion, tungsten-binder interface decohesion, binder rupture and tungsten cleavage, are identified as a function of temperature. The observed variations are explained in terms of the flow stress temperature dependence of the two phases within the alloy. The results are consistent with a changing mode of specimen rupture from one of a localized cascade of nucleation events at low temperatures to one of crack propagation through linking of cracks within the necked region of the specimens deformed at higher temperatures.