研究了挤压铸造过程中机械振动对A356 铝合金材料显微组织与力学性能的影响规律，并对机械振动击碎枝晶的作用机理进行了阐述。结果表明: 施加机械振动能够有效地消除材料缩松缩孔及断面裂纹，减少甚至消除挤压铸造铝合金铸锭的微观孔洞，细化晶粒组织，使得组织更加均匀; 挤压铸造凝固初期，机械振动能够在很大程度上破碎二次枝晶臂，增加材料的形核率; 试验值与理论值的对比分析表明，Kirkwood 模型具有更高的精度; 机械振动能够提高材料的力学性能，相较于重力铸造与无振动挤压铸造而言，所得铸件的抗拉强度与延伸率均有一定提高．

In this paper,the effects of mechanical vibration on the microstructure and mechanical properties of A356 aluminum alloy were experimentally investigated,and the mechanism of dendrite breaking under the action of mechanical vibration was explored.The results show that ( 1) mechanical vibration helps to effectively eliminate material's shrinkage hole and section crack during the squeeze casting,reduce or even eliminate the micro casting pores in aluminum alloy and refine the grain structure,thus resulting in more compact microstructure; ( 2) in the initial solidification stage of the squeeze casting,to a large extent,mechanical vibration can break the secondary dendrite arms and increase the nucleation rate of materials; ( 3) the Kirkword model is of higher accuracy which is proved by a comparison between the experimental and the theoretical results; and ( 4) as compared with the gravity casting and the squeeze casting without mechanical vibration,the casting with mechanical vibration significantly improves the mechanical properties of aluminum alloy and achieves higher tensile strength as well as more elongation.