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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。
SiCp / AZ91 magnesium matrix composites (MMCs) with volume fractions of 2%, 5%, 10% and 15% were studied by means of corrosion weight loss and electrochemical measurements combined with SEM and TEM analysis. Corrosion behavior in 3.5% NaCl solution containing saturated Mg (OH) 2 at 25 ℃. The results show that the corrosion rate of SiCp / AZ91 MMCs is obviously higher than that of AZ91 magnesium alloy, and increases with the increase of SiC particle volume fraction. The SiC particles do not directly form the microcouples with the AZ91 matrix, but the addition of SiC particles changes the microstructure of the SiCp / AZ91 MMCs to increase the corrosion rate. The main reason is that with the addition of SiC particles, the β-phase grain refinement increases the micro-galvanic corrosion current density between β-phase and α-phase. The addition of SiC particles makes a large amount of β-phase preferential at the interface between SiC particles and AZ91 matrix Recrystallization, resulting in the interface between the β-phase and α-phase micro-galvanic corrosion acceleration, indirectly lead to accelerated corrosion of SiCp / AZ91 MMCs.