The mutual exclusion between strength and ductility has been a long-standing problem in the field of materials science, especially in metal matrix composites (MMCs). Here we report the discovery of an unprecedented combination of high strength and high ductility within the copper matrix composites reinforced by super-aligned carbon nanotube (SACNT) films distributed with a gradient. The high strength (302 MPa) and high ductility (11.5%) are simultaneously achieved in this gradient-structured MMCs. The SACNT volume fraction gradient induces a plastic strain gradient and subsequent development of geometrically necessary dislocations (GNDs) near the boundaries. High back stress and extra strain hardening derived from the pile-up of GNDs are responsible for the superior mechanical properties. These observations shed light on the development of strong and ductile MMCs by architecting gradient structures.

强度和延展性之间的相互排斥是材料科学领域的一个长期存在的问题，特别是在金属基复合材料（MMC）中。在这里，我们报告了在由梯度分布的超取向碳纳米管（SACNT）膜增强的铜基复合材料中发现了前所未有的高强度和高延展性的组合。在这种梯度结构的MMC中，可以同时实现高强度（302 MPa）和高延展性（11.5％）。SACNT的体积分数梯度会引起塑性应变梯度，并在边界附近引发几何上必要的位错（GND）。GND的堆积产生的高背应力和额外的应变硬化是其优越的机械性能的原因。