【摘要】 利用腐蚀失重和电化学测试方法,并结合SEM和TEM分析技术,研究增强相SiC颗粒的体积分数为2%,5%,10%和15%的SiCp/AZ91镁基复合材料(MMCs),在25℃条件下,含有饱和Mg(OH)2的3.5%NaCl溶液中的腐蚀行为。结果表明,SiCp/AZ91 MMCs的腐蚀速率明显大于AZ91镁合金,并且随SiC颗粒体积分数的增加而增大。SiC颗粒不与AZ91基体直接构成微电偶,但是SiC颗粒的加入改变了SiCp/AZ91 MMCs的显微结构从而提高了腐蚀速率。主要原因为随着SiC颗粒的加入β相晶粒细化,使β相与α相间的微电偶腐蚀电流密度增大;SiC颗粒的加入使大量的β相在SiC颗粒与AZ91基体界面处优先再结晶,致使该界面处β相与α相间的微电偶腐蚀加速,间接导致SiCp/AZ91 MMCs的腐蚀加速。更多还原

【Abstract】 The corrosion behavior of the hot- extruded SiCp/AZ91(MMCs), a magnesium alloy AZ91 based composite containing different amount SiC particles(i.e. 2%, 5%, 10% and 20% in volume fraction), was investigated in 3.5%NaCl solution saturated by Mg(OH)2at 25 ℃ by means of mass loss method, electrochemical measurements, SEM and TEM observations and XRD. The results indicated that: The corrosion rate of the SiCp/AZ91 MMCs was much greater than that of AZ91 magnesium alloy, and which increased as the increasing volume fraction of micron- sized SiC. The strengthening SiC particles exhibited little tendency with the alloy matrix to form galvanic couple, thereby little tendency to induce galvanic corrosion in micro-scale. But the addition of SiC particles resulted in a highly change in microstructure of SiCp/AZ91 MMCs, as consequence, the corrosion resistance of the composite became significant inferior, in comparison with those of the AZ91 alloy. There were two main reasons responsible for the greater corrosion rate of SiCp/ AZ91 MMCs. Firstly, SiC particles promoted grain refinement of β phase, which increased the mi-cro-galvanic corrosion current density between β phase and α phase. Secondly, the addition of SiC particles promoted the dynamic recrystallization nucleation of β phase at the interface SiC particles/AZ91 matrix, which might be beneficial to the microgalvanic corrosion of the coupling of β phase and α phase there, therewith indirectly increased the corrosion rate of SiCp/AZ91 MMCs.更多还原