TiB_(2P)/2024Al复合材料高周疲劳损伤机制

Damage mechanism of TiB_(2P)/2024Al composite in high-cyclic fatigue

为了研究颗粒增强金属基复合材料的高周疲劳损伤机制,对压力浸渗法制备的TiB2P/2024Al复合材料进行了轴向疲劳实验,采用扫描电子显微镜观察了疲劳断口.结果表明:裂纹多萌生于材料的内部缺陷处;损伤模式主要为基体微孔聚集型损伤和颗粒-基体之间界面脱黏,颗粒开裂现象极少;裂纹的主要扩展区呈现韧窝和细小疲劳辉纹共存的特征.较小的增强颗粒降低了材料内部局部应力集中,弥散化了损伤的萌生位置的空间分布,增加了微裂纹的偏折和分岔的可能性,充分发挥了基体的塑性,进而提高了材料的疲劳性能.

To investigate the damage mechanism of TiB2P/2024Al composites in high-cyclic fatigue, fatigue experiments were carried out. SEM micrographs of fracture surfaces indicated that fatigue cracks initiated at interior defects of the composites. The dominate damage modes were porous assembling type axial mostly damage in matrix and interface debonding, scarcely any particle cracking. And coexistences of dimples and fatigue striations were observed in main propagation zone. The intrinsic mechanism governing the enhanced fatigue fracture characteristics are that, since the enforced particulate dimension is between sub-micron and micron level, lesser particles decrease stress concentration, disperse damage initiation sites, and increase the probability of crack deflection and bifurcation, then, the matrix plasticity exerts adequately. Therefore, the composites exhibit high fatigue resistance.