喷射沉积Al-20Si/SiCp复合材料的热疲劳行为

Thermal Fatigue Behavior of Spray Deposited Al-20Si/SiCp Composite

采用V型缺口试样对喷射沉积Al-20Si/SiCp复合材料进行了热循环试验,用光学金相显微镜和扫描电镜研究了在热应力作用下的热疲劳裂纹扩展方式和形态.结果表明:热疲劳裂纹优先在V型缺口处萌生;复合材料经一定的热循环次数后随相对密度的提高,裂纹扩展速率下降;在复合材料的三大相——α-Al基体、Si相以及SiC颗粒中,α-Al基体阻碍热疲劳裂纹的扩展,裂纹非连续性扩展;裂纹扩展方式受Si相的尺寸和分布状态控制,裂纹绕过Si颗粒向前扩展以及裂纹穿过Si颗粒向前扩展是裂纹碰到Si颗粒时常出现的两种机制;SiC颗粒与热疲劳裂纹有强烈的交互作用,加强SiC颗粒与基体的界面结合有利于提高热疲劳寿命.

Al-20Si/SiCp composite was fabricated by spray deposition. The thermal fatigue behavior of Al-20Si/SiCp composite was investigated in the water-quench method. Optical microscopy （OM） and scan- ning electron microscopy （SEM） were used to examine the damage mechanisms of thermal fatigue. Almost all the primary fatigue cracks at an elevated temperature initiated at V-notch. After several thermal cycles, the speed rate of crack propagation decreased with the relative density of composite increase. Because-Al matrix could stop crack from propagation, it resulted in un-continuous crack. The propagation mode of crack was controlled by the size and distribution of Si particles. Crack propagating through the Si particles and around Si particles were observed. Also, the fracture of SiC particles and the interfacial debonding between SiC particles and matrix were the principle mechanisms of interaction between SiC particles and matrix.