喷射沉积SiC_p/Al-20Si复合材料高周疲劳行为研究

Research on High-cycle Fatigue Behavior of Spray Deposited SiC_p/Al-20Si Composite

采用喷射沉积法制备15%(体积分数)4.5 m SiCp/Al-20Si复合材料及其基体合金,研究该组材料的微观组织、力学性能、高周疲劳性能以及疲劳断口形貌。结果表明:SiC颗粒的加入有利于提高材料的力学性能;复合材料及其基体的高调疲劳寿命随应力幅值的减小而增加,在相同应力幅值下,复合材料的疲劳寿命远远高于基体合金。疲劳裂纹从大颗粒的初晶Si的断裂以及Si相脱离处形核,并开始扩展。对于复合材料而言,SiC颗粒尺寸较小,不容易发生断裂,在形核过程中,当裂纹遇到SiC颗粒时,裂纹或者避开增强体,或者受阻于SiC颗粒,只能在基体合金中扩展,从而扩大了疲劳形核区的面积,提高了材料的疲劳寿命。Si颗粒的脱离、Si相的断裂以及SiC颗粒与基体界面的脱粘是复合材料疲劳断裂失效的主要机制。

15%（volume fraction） SiCp/Al-20Si composite and its matrix alloy is fabricated by spray deposition.The microstructures,mechanical properties,high-cycle fatigue properties and fatigue facture surfaces of composite and its matrix alloy are investigated,respectively.The results show that the high-cycle fatigue properties of SiCp/Al-20Si composite are superior,for SiC particles improve the mechanical properties of composite.Fatigue cracks initiate in the place where the primary Si fractured and the interfacial debonding between Si and matrix.For composite materials,SiC particles expanded fatigue nucleation area,improved the fatigue life of composite.The fracture of Si and the interfacial debonding including both Al/Si and Al/SiC are the principle mechanisms of the fatigue fracture of composite materials.