1989 Volume 53 Issue 1 Pages 34-41
Correlations between the tensile mechanical properties and ordering process have been investigated for Ni3Fe single crystals. Ordering processes were observed by electron microscopy and X-ray diffraction. The ordering process at 743 K observed by electron microscopy showed first the ordered spots of diffraction, then weak contrast of the anti-phase domain (APD), and finally swirllike APD with a size of 50 nm. The critical resolved shear stress (CRSS) first increased gradually, reached a peak, and then decreased to almost a constant value. The increase of CRSS was attributed to the coexistence of the ordered phase matrix and a small amount of the disordered phase. Slip morphology changed from coarse- and band-like to fine as ordering proceeds. Strain hardening in the disordered state was well characterized by well-defined easy glide region and the linear hardening region while that in the fully ordered state showed an exponentially increased hardening rate. It was suggested that the strain hardening in the latter state was due to the interaction between primary slip and microscopically activated secondary slip. Elongation basically did not decrease with proceeding of the ordering but rather increased depending on the tensile orientation of single crystals. Thus, the obtained elongation value depended upon the actually activated primary slip by which the homogeneous deformation was guaranteed regardless of the ordered state or disordered state.
