"Mechanics of extremely heterogeneous materials"
Our recent studies of 3D-printed alloys (Nature, 608, 62–68, 2022), high-entropy alloys with nanoscale chemical modulation (Nature, 574, 223-227, 2019), gradient nanotwinned metals (PNAS, 119, e2116808119, 2022), and several other heterogeneous materials raise fundamental questions about the role of extremely fine microstructural heterogeneities in controlling the mechanical behavior of these novel material systems. We combine mechanics modeling and experimental characterization to unravel the extra strengthening effects of microstructural gradients relative to their homogeneous counterparts. Quantitative comparisons are made between modeling and experimental results, highlighting the less appreciated notion of back-stress hardening with various types in materials with extremely complex microstructural heterogeneities. Furthermore, we have developed new experimental approaches, including in situ atomic resolution TEM (Science, 375, 1261–1265, 2022) and in situ synchrotron micro-diffraction X-ray, to push the limits of characterizing heterogeneous microstructures at different length scales. These techniques enable us to gain mechanistic insights for further enhancing the strength-ductility synergy in the design of extremely heterogeneous materials.
