Fundamental strengthening mechanisms of ordered gradient nanotwinned metals

Ordered structures with functional units offer the potential for enhanced performance in metallic materials. Among these structures, gradient nanotwinned (GNT) microstructures demonstrate excellent controllability. This paper provides a comprehensive review of the current state-of-the-art studies on GNT structures, encompassing various aspects such as design strategies, mechanical properties characterization, spatially gradient strain evolution analysis, and the significant role of geometrically necessary dislocations (GNDs). The primary objective is to systematically unravel the fundamental strengthening mechanisms by gaining an in-depth understanding of the deformation behavior of nanotwinned units. Through this work, we aim to contribute to the broader field of materials science by consolidating knowledge and providing insights for the development of novel metallic materials with enhanced properties and tailored performance characteristics.