Can experiment determine the stacking fault energy of metastable alloys?

Stacking fault energy (SFE) plays an important role in deformation mechanisms and mechanical properties of face-centered cubic (fcc) metals alloys. In many concentrated fcc alloys, the SFEs determined from density functional theory (DFT) calculations experimental methods are found having opposite signs. Here, we show that negative SFE by DFT reflects thermodynamic instability phase relative to hexagonal close-packed one; while experimentally restricted be positive models behind indirect measurements. We argue common underlying measurements fail metastable various solid solutions, demonstrate obtained correlate well with primary observed experimentally, showing a better resolution than measured SFEs. Furthermore, believe is for understanding abnormal behaviors partial dislocations alloys under deformation. The present work advances fundamental its relation plastic deformations, sheds light on future alloy design physical metallurgy.