中低应变量冷轧AA1050铝合金中晶粒取向与形变位错界面的演变

采用ECC和EBSD技术研究了AA1050铝合金冷轧至中低应变量下位错界面结构的演变. 结果表明, 冷轧至中低应变量下形成典 型的位错胞块结构,其微观组织结构强烈依赖于晶粒的取向. 变形后主要形成三种典型的组织结构: Type A------两组交叉的几何必须位错界面 (GNBs) 结构,Type B------一组GNBs结构, Type C------近似等轴的普通胞状结构. 绝大多数Copper, Brass和Goss取向的晶粒具有Type A结构, S取向的晶粒具有Type B结构, 而Cube取向的晶粒主要具有Type C结构. 变形过程中的GNBs不仅具有与RD成±(30°---40°) 的宏观取向, 而且大多数GNBs位错界面近似平行于由最大Schmid因子所确定的{111}滑移面的迹线.

EVOLUTIONS OF GRAIN ORIENTATION AND DISLOCATION BOUNDARY IN AA1050 ALUMINUM ALLOY DURING COLD ROLLING FROM LOW TO MEDIUM STRAINS

The dislocation boundary structure evolution in AA1050 aluminum alloy during cold rolling from low to medium strains was investigated using electron channeling contrast (ECC) imaging and the electron backscattered diffraction (EBSD) techniques. The results show that the grains are subdivided into a typical cell--block structure and there is a strong correlation between deformation microstructure and grain orientation. Based on the characterizations of grain subdivision and dislocation boundary structure, grains can be classified into three types: Type A---grains containing two sets of geometrically necessary boundaries (GNBs), Type B---grains containing one set of GNBs, and Type C---grains consisting of large dislocation cells structure. Most of grains with Copper, Brass and Goss orientations have Type A microstructure; grains with S orientation have Type B microstructure, grains with Cube orientation have Type C microstructure. The alignment of the extended dislocation boundaries depends strongly on the grain orientation. In most grains the boundaries have inclination angles of ±(30°---40°) to rolling direction (RD), and are approximately parallel to the traces of the most active {111} slip planes as identified by a Schmid factor analysis.