挤压态喷射成形Mg12Al1.5Zn6.5Ca1Nd镁合金组织及力学性能

Microstructure and Mechanical Properties of As-extruded Spray Forming Mg12Al1.5Zn6.5Ca1Nd Alloy

摘要:

利用喷射成形技术制备了Mg12Al1.5Zn6.5Ca1Nd镁合金，采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等测试手段，研究了挤压态实验合金的微观组织及力学性能。结果表明: 挤压态实验合金组织主要由α-Mg和Al2Ca组成，合金组织为等轴晶，晶粒大小约为2 μm, 第二相Al2Ca颗粒主要弥散分布在晶界处，颗粒平均尺寸小于1 μm; 基体内存在位错网及位错塞积，Al2Ca相中存在孪晶结构；合金抗拉强度(σb)、屈服强度(σ0.2)、延伸率(δ)分别为470 MPa、350 MPa、4.7%，主要强化方式为细晶强化、弥散强化、固溶强化；断口存在微孔聚合形成的孔洞，孔洞底部的杂质相或孔洞周围硬脆相与基体之间易萌生微裂纹，合金断裂机制为微孔聚合型沿晶断裂

Abstract:

The Mg12Al1.5Zn6.5Ca1Nd alloy was prepared by spray forming. The microstructure and mechanical properties of the as-extruded experimental alloy were investigated by XRD, SEM, TEM and EDS. The results show that the microstructure of the experimental alloy consists of α-Mg and Al2Ca, the microstructure is equiaxial grain, and the grain size is about 2 μm. The size of dispersive Al2Ca phase is less than 1 μm, which distributes mainly along the grain boundaries of the primary Mg. The dislocation pile-up in matrix Mg and twin structure in Al2Ca are observed by TEM. The σb, σ0.2 and δ of the alloy reach 470 MPa, 350 MPa and 4.7%, respectively. The main strengthening methods are fine grain strengthening, dispersion strengthening and solid solution strengthening. The fracture morphologies indicate the micro cracks nucleate between the impurity at the bottom of holes or the hard phase around the holes and the matrix. Holes are formed through micropores aggregation in the fracture. The fracture mechanism is microporous polymeric intergranular fracture