摘要
The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray diffractometry, scanning electron microscopy and electron backscattered diffraction technique while corrosion behavior was evaluated using linear/cyclic potentiodynamic, electrochemical impedance spectroscopy and ASTM–G67 tests. The composite contains sub-micron TiB2 particles in an aluminum matrix with both blocky and fine clusters of Al3Ti agglomerated around TiB2 and displays a low uniform corrosion rate. It is also resistant to pitting as substantiated by the absence of a positive loop in cyclic potentiodynamic tests. This is due to the non-conductive nature of TiB2 particles and a controlled amount of blocky Al3Ti phase. However, both friction stir processed and as-cast composites are susceptible to inter-granular corrosion where Al3Ti and TiB2 at grain boundaries provide initiation sites for corrosion. Electrochemical impedance study attributes this to the adverse effect of Al3Ti and TiB2 on the protective oxide surface film, which increases with immersion time.
研究铸态和搅拌摩擦加工后的Al-TiB2 基复合材料在3.5 wt.%氯化钠溶液中的显微组织和腐蚀行为。采用X 射线衍射、扫描电镜和电子背散射衍射技术对材料的显微组织进行表征,并采用线性/循环动电位极化、电化学阻抗谱和ASTM-G67 测试评估材料的腐蚀行为。结果显示,复合材料铝基体中含有亚微米级的TiB2 颗粒,其周围围绕着块状和细小的Al3Ti 团簇,材料表现出较低且均匀的腐蚀速率。在动电位循环测验中,没有出现正循环曲线,证明其具有抵抗点蚀的能力,这归因于TiB2 粒子的非导电性本质和块状Al3Ti 相的含量可控。然而,无论是搅拌摩擦加工态还是铸态复合材料都容易发生晶间腐蚀,晶界处的Al3Ti 和TiB2 是腐蚀的起始位点;电化学阻抗研究表明,这是由于Al3Ti 和TiB2 对保护氧化膜具有不利影响,且随着浸泡时间的增加,其不利影响增加。
基金
financial support from the Board for Research in Nuclear Sciences (BRNS) (Project number 36(2)/20/02/2014-BRNS/)
