Alloying behavior of binary to octonary alloys based on Cu-Ni-Al-Co-Cr-Fe-Ti-Mo during mechanical alloying

摘要

With an aim to bridge traditional alloys and high-entropy alloys with the alloying and amorphization behaviors, the present study used mechanical alloying (MA) to prepare a series of binary to octonary alloys selected from Cu, Ni, Al, Co, Cr, Fe, Ti, and Mo in sequence. Binary and ternary alloys formed FCC phase and BCC phase, respectively, and no amorphization was found even after 60 h milling. Quaternary to octonary alloys first formed FCC solid solution and then transformed into amorphous phase after prolonged milling. Thus, the first kind of amorphization process proposed by Weeber and Bakker based on binary systems also occurs in the present multi-principal-element alloys. The preference of FCC solution phase over BCC one is due to the easiest mixing of Cu, Ni, Al, and Co in the early stage in which Cu, Ni, and Co are FCC formers. The diffuse scattering in XRD reflecting the lattice distortion is arisen more significantly from the atomic size difference than that from heavy plastic deformation. A wider range of atomic size difference provided by more constituent elements is beneficial to form the amorphous structure and increase the diffuse scattering.