HRTEM Study of Precipitation Behavior in Mg-6 wt%Zn-1 wt%Y Alloy

The precipitation behavior in Mg-6 wt%Zn-1 wt%Y alloy annealed at different temperatures of $200^{\circ}C$ and $400^{\circ}C$ has been characterized by high resolution transmission electron microscope. When the alloy is annealed at $200^{\circ}C$ for 6 hr, the plate- and the rod-shaped ${\beta}_2 phases are precipitated in the matrix. The orientation relationship of plate-shaped precipitates with the matrix exhibits a [$11{\bar{2}}0]{\beta}_2$ || [$10{\bar{1}}0$]Mg, $(0001){\beta}_2 || (0001)Mg. While the rod-shaped precipitates have two kinds of the orientation relationships with the matrix, i.e. $[11{\bar{2}}0]{\beta}_2||[0001] Mg, $(0001){\beta}_2 Mg and $[11{\bar{2}}0]{\beta}_2||[0001] Mg, $({\bar{1}}106){\beta}_2 Mg. With increasing annealing time at $200^{\circ}C$ the ${\beta}_1 phases are also precipitated in the matrix and the orientation relationship exhibits a $[010]{\beta}_1 || [0001]Mg, $(603){\beta}_1 || ($01{\bar{1}}0$)Mg between the ${\beta}_1 precipitate and the matrix. The icosahedral phases are precipitated in the alloy annealed at $400^{\circ}C$ and exhibit a $[I2]_I$ || [0001]Mg relationship with the matrix.

고분해능 전자현미경을 이용한 Mg-6 wt%Zn-1 wt%Y 합금의 석출거동에 관한 연구