Microstructure and corrosion evolution of additively manufactured aluminium alloy AA7075 as a function of ageing

TL;DR

This study investigates how the microstructure, hardness, and corrosion behavior of additively manufactured AA7075 aluminium alloy evolve with artificial ageing, revealing distinctive microstructures and corrosion characteristics compared to wrought AA7075-T6.

Contribution

It provides new insights into the microstructure, corrosion, and hardness evolution of SLM-produced AA7075, a high-strength aluminium alloy, as a function of artificial ageing.

Findings

Additively manufactured AA7075 has a unique microstructure altered by ageing.

Corrosion response of AM AA7075 differs from wrought AA7075, with lower dissolution rates.

AM AA7075 exhibits smaller corrosion pits compared to wrought AA7075-T6.

Abstract

Additively manufactured high strength aluminium alloy AA7075 was prepared using selective laser melting. High strength aluminium alloys prepared by selective laser melting have not been widely studied to date. The evolution of microstructure and hardness, with the attendant corrosion, were investigated. Additively manufactured AA7075 was investigated both in the as-produced condition and as a function of artificial ageing. The microstructure of specimens prepared was studied using electron microscopy. Production of AA7075 by selective laser melting generated a unique microstructure, which was altered by solutionising and further altered by artificial ageing - resulting in microstructures distinctive to that of wrought AA7075-T6. The electrochemical response of additively manufactured AA7075 was dependent on processing history, and unique to wrought AA7075-T6, whereby dissolution rates were generally lower for additively manufactured AA7075. Furthermore, immersion exposure testing followed by microscopy, indicated different corrosion morphology for additively manufactured AA7075, whereby resultant pit size was notably smaller, in contrast to wrought AA7075-T6.