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Materials Data on CrNi2 by Materials Project

Ni2Cr crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cr is bonded to two equivalent Cr and ten equivalent Ni atoms to form CrCr2Ni10 cuboctahedra that share corners with two equivalent CrCr2Ni10 cuboctahedra, corners with ten equivalent NiCr5Ni7 cuboctahedra, edges with twelve equivalent CrCr2Ni10 cuboctahedra, edges with twelve equivalent NiCr5Ni7 cuboctahedra, faces with four equivalent CrCr2Ni10 cuboctahedra, and faces with fourteen equivalent NiCr5Ni7 cuboctahedra. Both Cr–Cr bond lengths are 2.47 Å. There are two shorter (2.48 Å) and eight longer (2.49 Å) Cr–Ni bond lengths. Ni is bonded to five equivalent Cr and seven equivalent Ni atoms to form NiCr5Ni7 cuboctahedra that share corners with five equivalent CrCr2Ni10 cuboctahedra, corners with seven equivalent NiCr5Ni7 cuboctahedra, edges with six equivalent CrCr2Ni10 cuboctahedra, edges with eighteen equivalent NiCr5Ni7 cuboctahedra, faces with seven equivalent CrCr2Ni10 cuboctahedra, and faces with eleven equivalent NiCr5Ni7 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.46–2.50 Å.

36 MATERIALS SCIENCE↗

Metastable formation and disordering kinetics of body-centered orthorhombic CrNi 2 laths in a Cr-Ni binary alloy

Chromium (Cr) alloys combine low density with high-temperature strength but suffer from brittleness and rapid softening. Body-centered orthorhombic (BCO) CrNi 2 laths have been shown to improve Cr-alloy high-temperature strength retention, yet their thermal stability and transformation behavior remain unclear. CrNi 2 conventionally forms through long-range ordering from a face-centered cubic (FCC) phase. Using multiscale microscopy and neutron diffraction, we show that CrNi 2 instead nucleates from a body-centered cubic (BCC) matrix, in a binary Cr 85 Ni 15 alloy. Despite aging above the equilibrium ordering temperature, CrNi 2 persists for ∼220 h at 760 °C before fully disordering, indicating sluggish transformation kinetics. The formation and decomposition follow differing transformation pathways (BCC → CrNi 2 → FCC), revealing kinetic asymmetry not captured by equilibrium Cr-Ni phase diagrams. In conclusion, these findings redefine the transformation behavior of CrNi 2 , establish its metastable kinetic window, and suggest alloying strategies to stabilize CrNi 2 for precipitation strengthening of high-temperature Cr-alloys.

CrNi2 transformation kinetics↗