铸造Al-Si合金Sr变质处理过程中共晶硅形态的渐变行为

Gradual Behavior of the Eutectic Si Morphology from Flake into Fiber in Al-Si Cast Alloy with Sr Modification

通过光学显微镜和SEM考察了共晶硅形态与大小随Al 11 6%Si合金中Sr量的变化。研究发现共晶硅从片状转变成纤维状的过程并不是突变的,而是一个渐变过程,共晶硅的形态存在一个介于二者之间的中间态,具有明显的弯折与分叉,同时也具有纤维硅的特征。随着合金中Sr量的增加,共晶过冷度增大,同时孪晶边界能降低,使得硅相产生弯折、分叉,硅相形态不断向纤维化转变。

The variation of morphology and size of the eutectic silicon with strontium content in Al-11.6%Si cast alloy was investigated by the optical microscope and scanning electron microscope. It is found that the change of the morphology of the eutectic silicon from flake into fiber is not mutational, but gradual. There is a medial morphology of the eutectic silicon between flake and fiber, with obvious bends and branches. With increase of the strontium content in the alloy, the eutectic undercooling degree was increased and the boundary energy of twin crystal was also minimized, and hence, it is relatively easy for the eutectic silicon crystals to bend and branch, so the morphology of the eutectic silicon gradually changes from flake into fiber.