Efficacy of α-β grade titanium alloy powder (Ti–6Al–2Sn–2Zr–2Mo–2Cr–0.25Si) in surface modification and corrosion mitigation in 3.5% NaCl on friction stir processed armour grade 7075-T651 aluminum alloys—insight in defence applications

Abstract

Aluminium alloy AA7075-T651 is one of the newest and promising commercials rolled sheet metal for structural applications in defensive areas like military, space and air vehicle, aerospace because of its excellent and unbeatable combination of high strength-to-weight ratio and good corrosion resistance, high fatigue strength. In this study friction stir processing (FSP) was performed on AA7075-T651 aluminium metal composite (AMC) reinforced with α-β grade Titanium alloy powder (Ti–6Al–2Sn–2Zr–2Mo–2Cr–0.25Si) which is an excellent reinforcement material in airframe and jet engine applications for corrosion resistance and exceptional strength-to-weight ratio. The processing parameters used were the rotational speed of 1500 rpm, processing speed of 20 mm min−1, and tilt angle of 3°. Two passes were carried out on the FSP parameters with 100% inter-pass overlap i.e. plunge depth of 0.3 mm was used which was distributed thus, 0.2 mm plunge depth on first pass and 0.1 mm plunge depth second pass. Mechanical characterization was carried out to study the influence of α-β grade Titanium alloy powder (Ti–6Al–2Sn–2Zr–2Mo–2Cr–0.25Si), in this tensile strength was studied using Xforce P type of Zwick/Roell Z250 tensile testing machine and surface roughness analysis was conducted on Mitutoyo surf test SJ-210 surface roughness tester. Corrosion behaviour of the processed AMC was studied using potentiodynamic polarization technique in 3.5% NaCl solution at an ambient temperature of 25°. It was established that α-β grade Titanium alloy powder as reinforcement inhibitor produced the highest percentage of inhibition performance efficiency (IPE) of 98.26% while the processed base metal (PBM) gave IPE of 63.99% with reference to the unprocessed base metal (UBM). There was an extraordinary improvement in corrosion rate with a reduction from 5.0718 mm/year to 0.087 675 mm/year when α-β grade Titanium alloy powder was used as inhibitor. AA7075-T651/Ti–6Al–2Sn–2Zr–2Mo–2Cr–0.25Si AMC has highest ultimate tensile strength (UTS) of 624 MPa which has a close value of 620.903 MPa to that of AA7075-T651 without reinforcement but the UTS for UBM was far away from them.