Microstructure, mechanical and corrosion behavior of 7075 aluminium alloy reinforced with nanostructured W-Ti alloy

Abstract

This work investigates the mechanical and electrochemical behavior of an Al-6Zn-2.5Mg-1.5Cu (wt%) (AA7075) composite containing nanocrystalline W-20 at% Ti (or W-20Ti) particles synthesized via vacuum hot pressing at 500 degrees C. In comparison to similarly processed monolithic AA7075, the AA7075-4(W-20Ti) composite shows a 16%, 33% and 45% higher hardness, tensile yield and flexural yield strength respectively. Electrochemical characterization in 3.5 wt% NaCl solution revealed that the AA7075-4(W-20Ti) composite exhibited an icorr of 3.60 f 0.72 mu A/cm2 which is comparable to that of monolithic AA7075 (3.30 f 0.41 mu A/cm2). Additionally, the introduction of W-20Ti reinforcement resulted in superior electrochemical stability in the composite, as evidenced by a well-defined passivation window of 318 f 18 mV, whereas AA7075 did not exhibit the same. This improved passivation behavior is ascribed to the increased release of Al3+ ions, induced by galvanic interactions between the matrix and the W-20Ti reinforcement, which promotes the formation of a protective corrosion product layer. The stabilization of this layer is further facilitated by WO3 species, effectively delaying the onset of pitting corrosion.