METALLIC MATERIALS WITH NANO-SCALE TWINS

Strengthening materials is a central objective of materials research.Traditional approaches to strengthen materials,including solid solution strengthening,second phase strengthening, grain refinement strengthening,dispersion strengthening and work hardening strengthening etc.,aim at creation of internal defects and boundaries so as to obstruct the motion of dislocations.Such strategies for strengthening invariably compromise the ductility and electrical conductivity of the material.By reviewing recent advances in our understanding of nanostructured metals and alloys,we propose a novel approach to optimize the strength,ductility and the electrical conductivity of materials by means of coherent twin boundaries at nano-meter scale.We assess current understanding of strengthening mechanism of twin boundaries(instead of incoherent boundaries as conventionally used).Additionally, some mechanical properties(such as strength,ductility,strain rate sensitivity,work hardening) and the physical properties(electrical conductivity and electrical migration) as well as the relative preparation techniques of the metallic materials with nano-scale twins will be reviewed in this paper.