Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

Abstract

In this paper, the microstructure and mechanical properties of AA7075 with a coarse-fine-grained laminated microstructure produced by spark plasma sintering (SPS) and the cyclic extrusion severe deformation (KOBO) technique were investigated. It was found that an inhomogeneous grain microstructure was formed from coarse and fine grains by the SPS process and then was transformed into a coarse-fine-grained laminated microstructure by means of KOBO extrusion at room temperature. The grain refinement during KOBO extrusion resulted in a fine grained laminated microstructure created due to the formation of low-angle grain boundaries (LAGBs), followed by dynamic recrystallization, leading to high-angle grain boundaries (HAGBs). The EBSD analysis results reveal the formation of a deformed and partially recrystallized ultrafine grain microstructure owing to the generation and development of shear bands during KOBO extrusion. The ultimate tensile strength (UTS) of the AA7075 alloy rose after SPS-KOBO severe deformation up to 422 MPa, with high strains of about 33%. The obtained results clearly show that the SPS-KOBO extrusion technique allows a bimodal laminated fine gradient grain microstructure to be obtained due to deformation and dynamic recrystallization, which result in both high strength and good ductility. The new heterogeneous AA7075 alloys obtained by the SPS-KOBO combined techniques demonstrate that microstructural heterogeneities can assist in overcoming the strength–ductility trade-off.

Feasibility Study on Modified Edge-Free Spark Plasma Sintering (SPS) on Metal Powder – Al7075 Case Study

“…However, the Vickers macrohardness -which encompass multiple grains -was higher for the SPTed Al7075 sample. This higher macrohardness which is consistent with observation reported elsewhere [17] is linked to the fact that elongated grains can hinder the movement of dislocations more effectively. The longer grain boundaries stemming from grain elongation provide more barriers for dislocations, making it more difficult for them to move freely.…”

“…In general, the microstructure obtained by both SPS AND SPT is heterogeneous due to the simultaneous presence of very large and fine grains. The observed heterogeneous microstructure is in good agreement with observations reported elsewhere [17].…”

Review on Micro-Alloying and Preparation Method of 7xxx Series Aluminum Alloys: Progresses and Prospects

“…The existing problem is still that the comprehensive performance of strength and toughness and stress-corrosion resistance are low. According to the aging precipitation [ 55 , 59 , 60 , 61 , 62 ], the phase, GBPs and PFZ of the precipitated alloy after aging determine the properties of the aluminum alloy. Reducing the slip of the eutectic surface and narrowing the PFZ of the grain boundary, optimizing the composition design of the alloy and improving the heat treatment method are the specific means to improve the comprehensive properties of the alloy [ 46 ].…”

Numerical optimization of sample and die geometric parameters to increase the attainable temperature during spark plasma sintering of TiC ceramics

“…The primary objective of incorporating thermal models in SPS operations is to optimize temperature profiles within the TiC sample and the surrounding system. This process allows for greater control over sintering, resulting in a more refined microstructure [22,23]. Given the critical role of SPS in the fabrication of UHTCs, this research focuses on a numerical exploration of temperature variations during the spark plasma sintering of titanium carbide ceramics.…”