科研之友
微信
新浪微博
Facebook
分享链接
摘要
Refining grains into nanoscale can significantly strengthen and harden metallic materials; however, nanograined metals generally exhibit low thermal stability, hindering their practical applications. In this work, we exploit the superposition of the contribution of nanotwins, low-angle grain boundaries, and microalloying to tailor superior combinations of high hardness and good thermal stability in Ni and Ni alloys. For the nanotwinned Ni having a twin thickness of similar to 2.9 nm and grain size of 28 nm, it exhibits a hardness over 8.0 GPa and an onset coarsening temperature of 623 K, both of which are well above those of nanograined Ni. Re/Mo microalloying can further improve the onset coarsening temperature to 773 K without comprising hardness. Our analyses reveal that high hardness is achieved via strengthen-ing offered by extremely fine nanotwins. Meanwhile, the superior thermal stability is mainly ascribed to the low driving force for grain growth induced by the low-angle columnar boundary architecture and to the additional pinning effect on the migration of twin/columnar boundaries provided by minor Re/Mo solutes. The present work not only reveals a family of nanotwinned metals possessing the combination of ultra-high hardness and high thermal stability but also provides a strategy for tailoring properties of metallic materials by pairing low-angle grain boundaries and twin boundaries.
-
单位中国科学院; y; 华中科技大学
