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

One of the principal obstacles to room temperature tensile ductility i n NiAl is an insufficient number of independent slip systems, due to t he sole operation of the [100]{011} system. It has been both predicted and reported that Cr additions to NiAl induce [111]{112} slip, increa sing the number of independent slip systems to five, a number sufficie nt for general plasticity. However, no attendant increase in tensile d uctility has been observed. The present study reexamines the effects o f Cr on the predominant room temperature slip system in polycrystallin e 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 N iAl at room temperature, while processing by extrusion, compared with casting and homogenization, produces a small, yet significant, proport ion of [110]{110} dislocations. Possible explanations for the discrepa ncy of the present results with those of previous work are discussed, as well as the presence and implications of the [110]{110} dislocation s.