微观组织与断裂行为
(北京工业大学 材料科学与工程学院，北京 100124)
摘 要: 采用多次循环塑性变形−原位反应方法制备Mg2Si/Mg-2Al-Zn-2Gd复合材料。采用XRD、SEM和TEM对复合材料的成分及微观组织进行分析和观察。结果表明：多次循环塑性变形过程对镁合金基体组织和原位合成的Mg2Si第二相粒子均有细化和均化作用；随着Mg2Si颗粒含量的增加，复合材料的弹性模量和屈服强度增加，同时断裂强度和伸长率均下降；原位反应合成的Mg2Si第二相粒子与基体结合良好，材料断裂时裂纹优先在基体中形成，断裂时Mg2Si第二相粒子能起到阻碍裂纹扩展的作用；Mg2Si/Mg-2Al-Zn-2Gd复合材料的强化机制主要为第二相强化和基体晶粒细化。
关键字: Mg2Si/Mg-2Al-Zn-2Gd复合材料；断裂行为；多次循环塑性变形；原位合成；Mg2Si
Mg2Si/Mg-2Al-Zn-2Gd composite
（School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China）
Abstract:The Mg2Si reinforced Mg-2Al-Zn-2Gd composite was synthesized by in-situ solid state reaction and repeated plastic deformation (RPW) process. The XRD, SEM and TEM analysis results indicate that the RPW method can significantly decrease the second phase particle size as well as the matrix crystalline size, and the elastic modulus and yield strength of the composite increase with increasing the volume fraction of Mg2Si whereas the fracture strength and strain decrease. The interface between Mg2Si and matrix is smooth, and no crack initiation source has been found on the interface. The propagation of cracks formed in matrix during fracture can be obstructed by the second phase, and the increase of mechanical properties of the composite is attributed to the dispersed Mg2Si second phase particle and the refined matrix grain size.
Key words: Mg2Si/Mg-2Al-Zn-2Gd composite; fracture behavior; repeated plastic deformation; in-situ synthesis; Mg2Si
