Probing the polytypic transition of Laves phase Cr₂Nb in the dual-phase Cr-20Nb-40Ti alloy

By employing XRD, EDXS, TEM, HRTEM, and SADPs methods, the polytypic transition of Laves phase Cr₂Nb alloyed with Ti has been investigated in the dual-phase Cr-20Nb-40Ti (in at.%) alloy. The solute Ti in Cr₂Nb is shown to inhibit the polytypic transition of Cr₂Nb by substituting onto the Cr sites. This leads to the occurrence of metastable structures of C36, 5R, 6H and 7R. On the contrary, the second phase β-Ti is suggested to prompt the polytypic transition of Cr₂Nb based on the lattice mismatch calculation. The low lattice mismatch between the β-Ti and the C15 polytype is beneficial to the formation of single C15 polytype at the interface.