Gradient materials have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures and/or composition gradually change from the surface to interior. The advantage of gradient materials is their maximization of physical and mechanical performance while minimizing material cost. Recently, gradient structured materials in engineering materials such as metals have been reported to produce a combination of high strength and good ductility that is not accessible to their coarse-grained counterparts. This is attributed to the mechanical incompatibility caused by the non-uniform deformation in the gradient structures, which produces complex stress states as well as stress/strain gradients, and consequently increases strength and strain hardening rates for high ductility. There is an interaction between mechanics and dislocation evolution in the gradient structure that need to be studied by a combined effort from the communities of both mechanics and materials science. On the other hand, a laminated structure consists of layers with different mechanical behaviors and has a similar mechanical incompatibility as the gradient materials, and its sharp interlayer boundaries make it an ideal model material to clarify some of the fundamental interplays between the mechanics and defect structure evolution that occurs in gradient materials.
Gradient and laminate materials are an emerging area with the potential to become a major research field for the communities of material, mechanics and physics. They also have potential in many applications such as strong and tough structures, energy efficient automobile, etc. There are many fundamental issues that need to be studied by experiments, analytical modeling and computer modeling. This symposium, and the symposia that will follow in the future, will act as a forum to bring multidisciplinary researchers together to exchange ideas, discuss key issues, and promote industrial technology development for commercial production and applications.