Abstract: Annealing twins is a common microstructure in face centered cubic metallic materials with low stacking fault energy. Craftsman makes speckled copper artworks by forging and high temperature heat treatment. However, they do not know the metallurgical theory behind the processing. Actually, the speckles in the copper artworks are the coarse annealing twins as a result of abnormal grain growth. With the development of modern metallurgy technique, people emphasized more on the microstructure control to obtain desired bulk properties. Twininduced grain boundary engineering is one of such technique to control and use the annealing twins.

Key words: annealing twins, copper artwork, grain boundary engineering, microstructure control