Microstructural aspects of formation and growth of short cracks in the Al(6061)/Al2O3 composite under LCF loading

在低周疲劳载荷下，Al(6061)/Al_2O_3-T6复合材料中的疲劳裂纹是与挤压和侵入有关的穿晶裂纹。新的裂缝会永久性地产生。它们与显微组织相互作用扩展，形成裂纹场。本项目的目的是研究颗粒增强Al(6061)/Al_2O_3-T6复合材料中疲劳短裂纹萌生和扩展的微观结构。晶粒取向，特别是韧性相中强化相的空间排列影响着穿晶疲劳裂纹的产生和扩展的变形模式的形成。计划将实验方法(LCF、REM、EBSD、扫描电子显微镜图像和层析图像的数字相关(DIC)测量变形场)与有限元模拟相结合。在实验数据的基础上，建立二维和三维有限元模型来模拟循环载荷作用下的裂纹路径。实验将记录疲劳寿命不同阶段的裂纹扩展和裂纹尖端塑性区(S)，并与模拟结果进行比较。这些方法和显微组织背景信息的结合将使更好地理解疲劳短裂纹在两相材料中的扩展动力学成为可能。

Fatigue cracks arise in the composite Al(6061)/Al2O3-T6 under LCF loading as transcrystalline cracks in connection with extrusions and intrusions. New cracks are permanently created. They propagate in interaction with the microstructure and form crack fields. The aim of this project is a research on the microstructural aspects of the initiation and growth of short fatigue cracks in the particle-reinforced Al(6061)/Al2O3-T6 composite. The grain orientations and, in particular, the spatial arrangement of the reinforcing phase within the ductile matrix phase influence the formation of deformation pattern in which the transcrystalline fatigue cracks are generated and propagate.It is planned to combine experimental methods (LCF, REM, EBSD, digital correlation of SEM pictures and tomograms (DIC) to measure deformation fields) with FE simulations. On the basis of the experimental data, 2- and 3-dimensional FE models of microstructure will be set up to simulate the crack path under cyclic loading. The crack propagation and the plastic zones around the crack tip(s) will be recorded experimentally at different stages of fatigue life and compared to the results of simulation. These combination of methods and microstructural background information will make it possible to better understand the propagation kinetics of short fatigue cracks in a two-phase material.