Thermodynamic Principles of Self-Healing Metallic Materials

Abstract

In this chapter, the thermodynamics of self-healing is considered with an emphasis on metallic materials. All complex biological organisms have the ability to repair minor damage. Incorporating the self-repair function into inorganic systems is of growing interest for materials scientists. So far, most recent studies have concentrated on polymers and ceramics because it is easier to incorporate self-healing in nonmetallic materials than in metallic materials. However, metallic self-healing alloys and composites are of great practical importance. We review the design principles of self-healing materials using the nonequilibrium thermody-namics approach and the concept of hierarchical organization. The generalized thermodynamic force that leads to healing is induced by bringing the system away from thermodynamic equilibrium. We focus on the three major methods of imparting the ability for self-healing in metallic systems: precipitation-induced healing, embedding shape-memory alloys, and embedding a low-melting point alloy in the alloy matrix.