The Effect of the Aging Time on Microstructure and Mechanical Properties of the AA7075 Alloy after T6 Heat Treatment

Abstract

In this study, the effect of the aging time on microstructure and mechanical properties of the AA7075 alloy after T6 heat treatment is investigated. The AA7075 alloys are quenched after solid solution treatment at 485°C for 2 hours and artificially aged at 120°C using five different aging times. Hardness measurements, microstructure examinations (SEM + EDS, XRD), and tensile tests are performed for the aged alloys. Fractured surfaces are also examined using SEM images after the tensile testing. The results of the studies conducted show that the hardness value of the alloys can be increased by increasing aging time, and the maximum hardness value of 192 HV is obtained for the alloy aged for 25 hours. Tensile tests also show that the tensile strength of the alloy can be increased by increasing aging time, and the maximum tensile strength value of 580 MPa is obtained for the alloy aged for 25 hours. Fractured surface examinations revealed that the ductile fracture mechanism is mostly dominant, while the planar fracture mechanism is observed as well.

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

“…Similarly, these tiny precipitates were crucial for the formation, growth, and coalescence of microvoids. Particularly, during the process of hot plastic deformation, the refined and hard precipitated phases were easily regarded as sites for void nucleation, which promoted the formation of microvoids, as has been confirmed by Simsek et al [ 35 ]. Then, the nucleation and growth of microvoids subjected to external loads accelerated the generation and deterioration of microcracks, as can be observed in Figure 9 .…”

“…Consequently, it should be noted that precipitate-induced damage also plays a comprehensive role. Simsek et al [ 35 ] believed that the fine and hard precipitated phases are easily used as the location of void nucleation, thus promoting the formation of microvoids. From the fracture morphology in Figure 10 a,b, there are precipitated phases with inclusions in the dimples [ 43 , 44 ].…”

A research on the effect of retrogression and re-aging heat treatment on hot tensile properties of AA7075 aluminum alloys

“…Aging heat treatment is commonly used for hardening aluminum alloys and improving their mechanical strength [2]. The hardness and strength of these alloys are increased by secondary phase precipitates formed in the microstructure and by obstructing/preventing the dislocation movement of these precipitates with the aging heat treatment [3,4]. The aging heat treatment is carried out in three stages.…”

“…The authors reported that an increase in the temperature of solution enabled the formation of secondary phase solutions, which led to an increase in hardness and strength. Şimşek et al [3] studied the effects of T6 heat treatment applied for different aging times on the microstructure and mechanical properties of AA7075 alloys. The researchers aged the alloys between 15 hours and 35 hours, observed that the samples that were aged for 25 hours showed the highest hardness and tensile strength values, and reported that the hardness and tensile strength decreased when the alloys were aged further.…”