Evaluation of Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy Repaired via Additive Friction Stir Deposition

Abstract

A novel solid-state additive manufacturing (AM) process, additive friction stir deposition (AFS-D), provides a new pathway for additively repairing damaged nonweldable aerospace materials that are susceptible to induced thermal gradients within the microstructure. In this work, we quantify the microstructural evolution and mechanical performance of an additively repaired AA7075-T651 (Al-Zn-Mg-Cu) via the AFS-D process. To evaluate the AFS-D process for repairing high strength aluminum alloys, the AFS-D technique was used to additively fill a linear groove that was machined into an AA7075-T651 plate. After repairing the plate with the AFS-D process, the repaired plate was subjected to standard T6 heat treatment. The results of this study show that the heat-treated AFS-D repair did not exhibit any significant grain growth and demonstrated an increase in the average Vickers hardness in the repair compared with the wrought 7075-T651 control. Tensile and fatigue behavior was investigated for heat-treated repair and compared with the wrought AA7075-T651 control. The heat-treated repair exhibited wrought-like tensile properties for yield stress (YS) and ultimate stress; however, the heat-treated repair had significant scatter in the elongation to failure. Additionally, the mean fatigue behavior of the heat-treated repairs displayed a reduction in cycles to failure compared with the wrought control. Lastly, a microstructure-sensitive fatigue life model was used to elucidate process-structure-property fatigue mechanism relations of the heat-treated repair and wrought AA7075.

Elucidating the Effect of Additive Friction Stir Deposition on the Resulting Microstructure and Mechanical Properties of Magnesium Alloy WE43

“…The deformed material is shaped by the tools path layer-by-layer until the desired component dimensions have been achieved. Each consecutive layer is re-stirred and metallurgically bonded to the previous layer due to the tool geometry described in Avery et al [21] and Robinson et al [22]. The AFSD process has the ability to produce a fully dense build with a refined and homogenous microstructure and exhibit wrought-like mechanical properties in materials such as structural and high-strength aluminum alloys [19][20][21][23][24][25][26][27][28][29][30][31][32][33], magnesium alloys [22], and Inconel alloys [18,34].…”

Ballistic Evaluation of Aluminum Alloy (AA) 7075 Plate Repaired by Additive Friction Stir Deposition Using AA7075 Feedstock

“…Temperature gradients and severe plastic deformation during the AFSD process removed the T6511 temper in the as-deposited AA7075 and around the affected area, Heat Affected Zone (HAZ) where coarsening of the nano-scale Fig. 5 Ballistic damage of the front and back sides of the plates are compared between the AA7075 control plates and the AA7075 AFSD repaired plates that reveals macroscopic changes due to coarsening of strengthening precipitates in the as-deposited AA7075 material strengthening precipitates has been reported previously [23], resulting in different material properties as discussed subsequently.…”

“…AFSD is capable of generating high quality repairs free from voids and cracks along with low residual stresses, and high adhesion to the base material, making it a supremely attractive method for the repair of critical components such as vehicle or personnel protection systems [8]. Considerable research exists on the additive manufacturing capabilities of AFSD on a variety of aluminum alloys including A356 [9], AA5083 [10], AA6061 [11][12][13][14][15], AA7050 [16,17], and AA7075 [18,19]; but relatively little work exists on the repair capabilities [20][21][22][23][24]. There is also a fundamental lack of work elucidating the effectiveness of repaired AA7075 against subsequent ballistic impacts.…”

Microstructure Evolution of Al6061 Alloy Made by Additive Friction Stir Deposition

“…Localized heat can soften the feedstock to a pasty state, which is then fed through the tool and creates metallurgical bonding with the substrate or previous layer [ 22 ]. With the motion of the fabrication tool and designed layer thickness, feedstock is deposited on the substrate layer by layer to form 3D components [ 13 , 23 ]. Due to the obvious advantages, AFS-D has recently been drawing the attention of more and more researchers.…”