反复镦压AZ31-Mg2Si原位复合材料的组织和力学性能

摘要

AZ31−4.6% Mg2Si (mass fraction) composite was prepared by conventional casting method. Repetitive upsetting (RU) was applied to severely deforming the as-cast composite at 400 °C for 1, 3, and 5 passes. Finite element analysis of the material flow indicates that deformation concentrates in the bottom region of the sample after 1 pass, and much more uniform deformation is obtained after 5 passes. During multi-pass RU process, both dendritic and Chinese script type Mg2Si phases are broken up into smaller particles owing to the shear stress forced by the matrix. With the increasing number of RU passes, finer grain size and more homogeneous distribution of Mg2Si particles are obtained along with significant enhancement in both strength and ductility. AZ31−4.6%Mg2Si composite exhibits tensile strength of 284 MPa and elongation of 9.8%after 5 RU passes at 400 °C compared with the initial 128 MPa and 5.4%of original AZ31−4.6%Mg2Si composite.%采用常规铸造方法制备AZ31−4.6%Mg2Si复合材料，在400°C对铸态复合材料进行1、3和5道次的反复镦压(RU)剧烈变形。材料流动的有限元分析表明：1道次后变形集中于试样底部区域，5道次后可获得均匀的变形。多道次反复镦压过程中基体施加的剪切应力使树枝状和汉字状Mg2Si相破碎成小颗粒，随着反复镦压道次的增加，晶粒尺寸逐渐减小，Mg2Si颗粒分布逐渐均匀，同时强度和塑性显著提高，在400°C 反复镦压5道次后， AZ31−4.6% Mg2Si复合材料抗拉强度和伸长率分别为248 MPa和9.8%，而原始铸态复合材料的抗拉强度和伸长率分别只有128 MPa和5.4%。