Effect of swaging and rolling post sintering treatments on the corrosion behaviour of Alumix 321 PM alloy

Abstract

In this work, two post sintering hot deformation processes were applied on Alumix 321 PM alloy which is a commercially available aluminum powder alloy which can be considered equivalent to the wrought AA6061 alloy. The powder was compacted, sintered, and then either hot swaged or hot rolled. The results show that both hardness and density were improved as a result of the applied post sintering treatment. Theoretical density (TD) of 99.1% and 99.39% were recorded for the hot rolled and hot swaged alloys, respectively. T6 hardness improves to 106±6 HRE and 96±2 HRE for hot rolled and hot swaged alloys, respectively. The performance was assessed in terms of corrosion behaviour by testing the Alumix 321 PM alloy in as sintered, and as hot deformed conditions after exposure to 3.5wt% NaCl solution. Electrochemical techniques were used to study the effect of hot deformation on corrosion behaviour. Corrosion current density decreases as a result of hot swaging and hot rolling and in both cases the values were less than those of the wrought counterpart, AA6061 alloy. The stair step polarization was applied; the results obtained support that the technique seems promising to bridge the gap between traditional and accelerated corrosion test methods. Pitting was the main corrosion mechanism for the wrought alloy while, pitting, crevice, and intergranular corrosion were observed for the PM alloys.