Abnormal grain growth induced by cyclic heat treatment.
In polycrystalline materials, grain growth occurs at elevated temperatures to reduce the total area of grain boundaries with high energy. The grain growth rate usually slows down with annealing time, making it hard to obtain grains larger than a millimeter in size. We report a crystal growth method that employs only a cyclic heat treatment to obtain a single crystal of more than several centimeters in a copper-based shape-memory alloy. This abnormal grain growth phenomenon results from the formation of a subgrain structure introduced through phase transformation. These findings provide a method of fabricating a single-crystal or large-grain structure important for shape-memory properties, magnetic properties, and creep properties, among others.
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan. omori@material.tohoku.ac.jp
Toshihiro
T
Omori
Tomoe
T
Kusama
Shingo
S
Kawata
Ikuo
I
Ohnuma
Yuji
Y
Sutou
Yoshikazu
Y
Araki
Kiyohito
K
Ishida
Ryosuke
R
Kainuma