Influence of the Initial Temper Conditions and Post-Deposition Heat Treatments on the Friction Stir Deposition of AA7075.

Abstract

The present study aims to examine the influence of two different tempered condition of (T6) and (O) for the as received material and the post deposition heat treatment (PDHT) on the mechanical properties and the microstructure of the AA7075 aluminum alloy deposited via additive friction stir deposition technique. To achieve these goals, the AFSD experiment were conducted using 40 mm consumable rod of AA7075-T6 aluminum alloy on a substrate of AA2024-T4 at a constant rotation speed of 400 rev/min and deposition rate of 3 mm/min as a first step to produce continuously multi layers of AA7075-T6 and AA7075-O. The PDHT was the second step to study the enhancement the mechanical properties after the deposition process, using to different techniques retrogression re-ageing (RRA) and Re-ageing (RA). For the deposited materials the hardness and compression tests as mechanical properties were conducted. In addition, the (OM), (SEM) using an advanced EDS system, and XRD technique were used to analyse the microstructure features. The result showed that after AFSD process the hardness of the deposited AA7075-O increased by 25% but the deposited AA7075-T6 attains 90% of the as received consumable rod which was improved after the PDHT to achieve 28% improvement than the hardness value of the as received material. The compressive strength of the deposited material was higher than the initial material in both tempered conditions. The microstructure shows a recrystallized grains refinement throughout the deposited AA7075, which the gain size decreases from 25 µm ± 4 for the as received material.