超声处理协同Er和Ce复合变质对Mg-3.2Si合金组织及性能的影响

研究了超声处理协同稀土元素Er和Ce复合变质对过共晶Mg-3.2Si合金中组织和力学性能的影响,并探讨了其作用机理。结果表明,在过共晶Mg-3.2Si合金中,添加约0.6%(质量分数,下同)的Er时,初生Mg2Si相的尺寸由150μm减小到40μm,其形态从粗大树枝状变为不规则多面体形状;继续添加1.0%的Ce,可获得5～10μm的多面体或球状初生Mg2Si相,变质效果明显。在此基础上,超声处理可以有效改变初生Mg2Si相的形状和尺寸。当超声功率为1 200W时,可获得颗粒状的初生Mg2Si相,细化效果最佳,合金试样的抗拉强度与伸长率分别达到158MPa和4.5%。对其断口分析可知,经超声处理的合金断裂形式为解理断裂和韧窝的混合断裂形式。

Effects of Ultrasonic Treatment and Er-Ce Compound Modification on Microstructure and Mechanical Properties of Hypereutectic Mg-3.2Si Alloys

Effects of ultrasonic treatment and Er-Ce compound modification on microstructure and mechanical properties of hypereutectic Mg-3.2Si alloy were investigated,and the refining mechanism was described.The results reveal that with 0.6%(mass fraction,the same below)Er addition,the size of the primary Mg2 Si phase in the Mg-3.2Si alloy is decreased from 150μm to 40μm with strucutre transformed from bulky dendritic into irregular polyhedron shape.Then adding 1.0% Ce,polyhedron primary Mg2 Si phase with size of 5-10μm can be observed in the Mg-3.2Si alloy.With the increase of ultrasonic treatment power,the morphology,size and distribution of Mg2 Si in Mg-3.2Si alloy solidified structure can be improved obviously.With ultrasonic treatment power of1 200 W,the Mg2 Si phase in the alloy is changed into granulate structure,and its tensile strength and elongation reach 158 MPa and 4.5%,respectively.The fracture morphology of the Er-Ce compound modified Mg-3.2Si alloy after ultrasonic treated is characterized by as a mixed fracture form between cleavage fracture and dimple fracture.