Mingwei Zhang1,2,Flynn Walsh2,Madelyn Payne2,Punit Kumar1,2,Robert Ritchie1,2,Mark Asta1,2,Andrew Minor1,2
Lawrence Berkeley National Laboratory1,University of California, Berkeley2
Mingwei Zhang1,2,Flynn Walsh2,Madelyn Payne2,Punit Kumar1,2,Robert Ritchie1,2,Mark Asta1,2,Andrew Minor1,2
Lawrence Berkeley National Laboratory1,University of California, Berkeley2
The observation of diffuse superlattice intensities in many FCC high/medium entropy alloys by transmission electron microscopy has been attributed to the presence of chemical short-range order (CSRO). Namely, streaking, 1/3<422>, and 1/2<311> peaks were observed under electron diffraction along [110], [111], and [112] zone axes, respectively. However, displacive planar defects in FCC crystals (i.e., stacking faults or nanotwins) can produce the exact set of those peaks, making the interpretation ambiguous. In addition, our theoretical predictions of ordering reveal discrepancies between predicted superlattice peaks and observed ones. In this presentation, we discuss the origin of extra electron reflections in FCC concentrated solid solutions using the insights from our recent experiments and simulations as well as the implications on the mechanical properties. We will compare our TEM analysis of diffuse scattering and superlattice peaks with both diffraction contrast and high resolution electron microscopy imaging of defect structures.