SEMINAR
The State Key Lab of
High Performance Ceramics and Superfine Microstructure
Shanghai Institute of Ceramics, Chinese Academy of Sciences
中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室

Extra-electron induced covalent strengthening and its implication for the design of high-strength materials

Speaker

陈星秋 研究员

中国科学院金属研究所，沈阳材料科学国家（联合）实验室

时间：10月22日 （星期一）下午14:00

地点：2号楼607会议室

联系人：张文清研究员

Abstract

To control and understand strength and ductility of materials is always one of the most important issues for designs of innovative and high-performance materials, not only for practical applications but also for fundamental sciences. Traditional strengthening ways, such as strain, precipitation, and solid-solution, come into effect by pinning the motion of dislocation. Here, through first-principles calculations we report on an extra-electron induced covalent strengthening mechanism, which alters chemical bonding upon the introduction of extra-valence electrons in the matrix of parent materials.It is responsible for the brittle and high-strength properties of Al$_{12}$W-type compounds featured by the typical five-fold icosahedral cages, which are common for quasicrystals and bulk metallic glasses (BMGs).In combination with this mechanism, we generalize ductile-to-brittle criterion in a universal hyperbolic form by integrating the classic Pettifor's Cauchy pressure with Pugh's modulus ratio for a wide variety of materials with cubic lattices. This study also provides compelling evidence to correlate Pugh's modulus ratio with hardness of materials and may have implication for understanding the intrinsic brittleness of quasicrystals and BMGs.