硅酸铝纤维增强铝基复合材料的疲劳断裂特征

采用压力铸造法, 制得Al₂O₃?SiO₂短纤维增强的铝合金复合材料, 对其弯曲疲劳性能进行了测试, 并详细观察了疲劳裂纹的形成及扩展方式。结果表明: Al₂O₃?SiO₂f/ ZL 108复合材料存在 多种疲劳源; 疲劳裂纹的扩展是通过主裂纹与裂尖前方孔洞的相互联接而进行的, 是不连续的, 沿着纤维及渣球密集的路径扩展; 疲劳过程中主裂纹的形成消耗了大部分的疲劳寿命, 一旦主裂纹形成就快速扩展瞬间断裂。该复合材料的断裂宏观上是脆性的, 但微观上显示出塑性的特征。

SOME CHARACTERISTICS OF THE FATIGUE FRACTURE OF A KIND OF Al2O3·SiO2f /ZL108 COMPOSITE MATERIAL

The fatigue behaviour of the Al2O3·SiO2 fibre reinforced aluminum matrix composites produced by the squeeze casting method was investigated. The fatigue crack initiation and propagation were observed by SEM. It is found that the initiation of fatigue cracks is originated from different areas. The fatigue crack growth in the form of linking main cracks with the voids, formed at the tip of cracks, or in a discontinuous manner follows a fibre and shots concentrated path. During the fatigue process, the formation of the main crack expends most of the whole fatigue life, and once the main crack forms, the crack propagates rapidly and fractures immediately. It is believed that Al2O3·SiO2f /ZL108 composites show a characteristic of brittle fracture macroscopically, but the matrix of the composites still shows more ductility in microscopic characteristics.