7075-TiB_2原位铝基复合材料的腐蚀性能

Corrosion Performance of in Situ 7075-TiB_2 Aluminum Matrix Composites

采用动电位极化试验研究了7075-TiB2铝基复合材料的腐蚀行为。结果表明,该复合材料的腐蚀率与TiB2颗粒的比例成对应关系,而这主要与由原位TiB2颗粒引起的位错密度的增加有关。选择性点蚀具有晶粒间非对称的特点,主要归因于由TiB2颗粒与铝基体的热膨胀系数错配所致的局部位错密度不同。晶间腐蚀易于发生于大角度晶界,而特殊晶界和小角度晶界则表现出耐腐蚀性。晶内TiB2颗粒及其与铝基体的界面均无腐蚀发生。沿晶TiB2颗粒与晶界交汇的界面受晶间腐蚀的影响。

Potentiodynamic polarization testing was conducted to reveal the correspondence of corrosion rate with the fraction of TiB2 particulates of 7075-TiBz aluminum matrix composites （AMCs）. The corrosion behavior of the 7075- TiB2 AMCs was primarily related to the increase of dislocation density induced from TiB2 particulates. Preferential pitting corrosion with a characteristic of pitting asymmetry was mainly attributed to the differentiation of local dislocation density induced from mismatch of thermal expansion coefficient between the particulate and the aluminum matrix. Intergranular（IG） corrosion was liable to occur in high angle grain boundaries while special grain boundaries and low angle grain boundaries were corrosion-resistant. The intragranular TiB2 was observed to be immune to corrosion, while the grain boundary TiB2 particulate was affected by IG corrosion.