Grain boundary decohesion by nanoclustering Ni and Cr separately in CrMnFeCoNi high-entropy alloys.

The loss of ductility with temperature has been widely observed in tensile tests of single-phase face-centered cubic structured high-entropy alloys (HEAs). However, the fundamental mechanism for such a ductility loss remains unknown. Here, we show that ductility loss in the CrMnFeCoNi HEA upon deformation at intermediate temperatures is correlated with cracking at grain boundaries (GBs). Nanoclustering Cr, Ni, and Mn separately at GBs, as detected by atom probe tomography, reduces GB cohesion and promotes crack initiation along GBs. We further demonstrated a GB segregation engineering strategy to avoid ductility loss by shifting the fast segregation of principal elements from GBs into preexisting Cr-rich secondary phases. We believe that GB decohesion by nanoclustering multiprincipal elements is a common phenomenon in HEAs. This study not only provides insights into understanding ductility loss but also offers a strategy for tailoring ductility-temperature relations in HEAs.