Precipitation Behaviour of Zirconium Compounds in Zr-Bearing Al-Mg-Si Alloy
In commercial aluminum alloys, Zr is recognized as an important additional element improving their properties such as strength, corrosion resistivily, and so on. It forms very fine particles of the metastable Al3Zr phase with L12 ordered configuration, in the case of alloys without Si. On the other hand, the DO22-type (Al, Si)3Zr phase besides the L12-type Al3Zr phase is precipitated in alloys including large amounts of Si, such as 6000 series. In this study the main stress falls on precipitation behavior of these Zr compounds in a Zr bearing Al-Mg-Si alloy. The Al-0.67Mg-0.97Si-0.37Zr alloy was cast into a metal mold and hot-rolled to a 5 mm thick plate. A lot of fine L12-type Al3Zr particles were coherently precipitated in the matrix by aging the plate at 673K. The aged plate was cold-rolled to a 1 mm thick sheet and annealed at 553-813K, and then microstructure was investigated by using a transmission electron microscope. It was realized that fine coherent L12-type Al3Zr particles are transformed to incoherent and coarse DO22-type (Al, Si)3Zr particles through recrystallization. The DO22-type (Al, Si)3Zr particles reduced recrystallized grain size owing to their pinning effect.
W.J. Poole, M.A. Wells and D.J. Lloyd
Y. Himuro et al., "Precipitation Behaviour of Zirconium Compounds in Zr-Bearing Al-Mg-Si Alloy", Materials Science Forum, Vols. 519-521, pp. 501-506, 2006