Al-Cu-Mg-Ag合金中半共格Ω析出相与位错的交互作用

Interaction Between Semi-coherentΩPrecipitates and Dislocations in Al-Cu-Mg-Ag Alloy

通过透射电子显微镜和高分辨透射电子显微镜研究了Al-Cu-Mg-Ag合金在变形过程中位错与Ω析出相的交互作用.研究表明:对于与基体呈半共格的Ω相,位错在变形过程中是切割过而不是绕过Ω相.位错切割Ω相形成的衬度变化以及细小的台阶可通过透射电子显徽暗场相和高分辨电子显微镜观察到.位错切割Ω相后留下由一系列同号位错组成的台阶,台阶的界面有很高的应变能.这种高的应变能阻碍了位错的连续切割,使得台阶的同一位置及附近只能被位错切割有限的次数,从而限制了台阶的高度.在位错切割Ω相后留下的台阶附近,原子的周期性排列遭到破坏,形成了一个刃性位错.由于Ω相与Al基体有不同的晶体结构,因此其滑移系(滑移方向与滑移量的大小)不同,位错在基体中的滑移方向是沿[011]方向,而在Ω相中的滑移方向是沿[001]方向,2个滑移方向有近30°的夹角.

The interaction between dislocations and Ω phases in Al-Cu-Mg-Ag alloy during deformation has been studied by traditional transmission electron microscopy and high resolution transmission electron microscopy. It has been shown that dislocations cut through instead of loop around the Ω hases, which have semi- coherent relationship with the Al matrix. The color variation and steps due to the dislocation cutting can be observed by TEM dark field and HRTEM. Steps were made by a series of dislocations with high strain energy. This high strain energy inhibits dislocations cutting at the same position or around the step continuously, thus limits the height of the steps. The atom periodical distribution has been destroyed and an edge dislocation forms around the step caused by dislocation cutting the Ω phase. The slip systems （slip direction and slip magnitude） are different for Ω phase and Al matrix due to the variation in crystal structure. The slip directions of dislocation are along the [0 1 1 ] and [001 ] in the matrix and Ω phase, respectively, with about 30° angle.