Cu–Zn合金の変形双晶形成に及ぼす初期集合組織の影響

抄録

Heavily and simply cold–rolled Cu alloys with ultra–low stacking fault energy exhibit superior strength/ductility balance. The excellent mechanical properties are attained by the formation of a heterogeneous–nano （HN） structure consisting of twin domains, shear bands, and lamellar grains. In this study, using a Cu–Zn system alloy, two specimens with different initial textures were subjected to cold rolling. One has a strong <001> texture along the normal direction (ND) of the rolling surface, and the other has a <111> texture. Then, the effects of the initial texture of specimens on the formation of deformation twins in the early stage of cold rolling were precisely investigated. Also, the microstructure and mechanical properties of the alloys with finally developed HN structure after 90％–cold–rolling were examined. At the early stage of rolling, the mechanical twinning occurred more frequently in the specimen with <001> texture than in the <111> one. The difference in the twinning frequency can be reasonably explained by the significant difference in the ratio of the Schmid factor for twinning partial to the one for the perfect dislocation. On the 90％ cold rolling, the <001> specimen exhibited better strength/ductility balance than that of the <111> specimen since the <001> one has a higher volume fraction of the deformation twin domains. It can be concluded that the initial texture of the specimen before the cold rolling plays an important role in the mechanical properties of HN structured materials via the formation of the twin domains.