Corrosion Performance of in Situ 7075-TiB₂ Aluminum Matrix Composites

Potentiodynamic polarization testing was conducted to reveal the correspondence of corrosion rate with the fraction of TiB2 particulates of 7075-TiB2 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.