THE EFFECTS OF CHROMIUM ON NIAL INTERMETALLIC ALLOYS .2. SLIP SYSTEMS

One of the principal obstacles to room temperature tensile ductility in NiAl is an insufficient number of independent slip systems, due to the sole operation of the [100]{011} system. It has been both predicted and reported that Cr additions to NiAl induce [111]{112} slip, increasing the number of independent slip systems to five, a number sufficient for general plasticity. However, no attendant increase in tensile ductility has been observed. The present study reexamines the effects of Cr on the predominant room temperature slip system in polycrystalline NiAl, as a function of Cr content, Ni/Al ratio and processing route. It is shown that Cr has essentially no effect on the slip system in NiAl at room temperature, while processing by extrusion, compared with casting and homogenization, produces a small, yet significant, proportion of [110]{110} dislocations. Possible explanations for the discrepancy of the present results with those of previous work are discussed, as well as the presence and implications of the [110]{110} dislocations.