Research progress on gradient metallic materials

Facing the development of modern society and its economy,demands on metallic materials'propertis are ever increasing,including high strength and toughness, high wear resistance, high corrosion resistance, and high fatigue performance, et al. Gradient materials are a kind of materials that change gradually with a gradient from one constituent to another, including composition gradient, phase gradient, and grain size gradient or combination of the above. The gradient structures not only could effectively avoid the sudden change in properties caused by interface, but also coordinate the deformation of various feature sizes, and achieve the improvement of strength and ductility at the same time. In this paper, the concept and classification of the gradient materials are introduced, and the possible ways to produce gradient materials and the mechanism to improve multiple material properties are discussed. As one of the promising areas, gradient materials are expected to achieve the major advances in improving materials' properties and multifunctionality, and widely to be used in the application in near future.