Deformation induced alpha and epsilon martensites in Fe-Ni-Cr single crystals

The orientation dependence of an applied tensile stress on the formation of specific α martensite variants of the Kurdjumov-Sachs (K-S) orientation relationship in Fe-15Ni-15Cr single crystals are presented. Test temperatures were 185, 242 and 273 K,i.e., aboveM _s. Quantitative volume fraction measurements of deformation induceda ande martensite were made on crystals with the [100]γ, [1•10]γ, [•1•12]γ and [•2•13]γ tensile axes, α-martensite was only observed after 5 pct strain at 185K in all orientations, but the total volume fraction ofa martensite varied from <0.002 to 0.07 for the [100]γ and [•2•13]γ tensile axes respectively. The distribution of the K-S variants was also found to be sensitive to the direction of the applied stress, and 80 pet of the α martensite present in crystals oriented for easy glide had the same K-S variant. Epsilon martensite was found in all specimens but occurred only in the (111) planes which had slipped. Glen Stone, formerly graduate student, University of California at Berkeley