Tough ultrafine-grained Ti through multilayering and grading

The mechanical performance of ultrafine-grained metals can be enhanced through multilayering and grading. The mechanical gradation across the layers and in the junctions between layers achieves a more gradual stress redistribution, providing robustness to catastrophic failure. A mechanics model is established to explain the crack-stopping effect of the multilayers. The material design principal reported here provides a valuable guide for the development of the nanograined/ultrafine-grained materials with high strength and toughness.