超声外场对SiCp/7085复合材料颗粒微观团聚与界面结合的作用机理

Mechanism of ultrasonic field on the particle micro-agglomeration and interfacial bonding of SiCp/7085 composites

采用半固态混合-机械搅拌-超声施振的方法制备了体积分数为10%的SiCp/7085复合材料,通过金相显微镜、扫描电镜和X射线衍射对颗粒分布与界面进行研究,重点研究超声外场对复合材料颗粒团聚与界面结合的作用机理.实验结果表明:单纯机械搅拌对400目颗粒的团聚与界面结合的作用效果有限;超声外场下,空化作用产生的微射流与瞬时高温高压能够有效破除颗粒团聚体的包裹层,打散颗粒;超声破除颗粒表面氧化膜,除去气体层,使熔体中的镁元素与颗粒直接接触并反应是改善熔体与颗粒润湿性的重要因素;最终在界面处生成MgAl_2O_4强化相,从而获得更优的界面结合.

SiCp/7085 composites with 10% particle volume fraction was prepared by a semi-solid mixture-mechanical stirring- ultrasound vibrations method. The particle distribution and interface bonding were studied through optical microscopy （ OM ） , scanning electron microscopy （SEM） and X-ray diffraction （XRD）, and the effect of ultrasonic field on the particle agglomeration and interra- cial bonding of the composites was studied emphatically. The experimental results indicate that the effect of mechanical stirring on the agglomeration and interracial bonding of 400 mesh particles is not significant. Under ultrasonic field, the coating of particles agglomer- ation can be effectively get rid of by instantaneous high pressure and temperature and micro jet induced by cavitation. That ultrasonic gets rid of the oxide film on the particle surface, removes the gas layer and makes magnesium in melt contact with particles directly is a very important factor in improving wettability between melt and particles. Finally, the MgAl2O4 strengthening phase is formed at the interface and a better interface bonding is got.