Effects of Different Heat Treatment Conditions on Fatigue Behavior of AA7075 Alloy

Abstract

In this study, the effect of different heat treatment processes applied to AA7075 alloys on the fatigue behavior was examined. The processes applied to AA7075 aluminum included annealing (O), high temperature pre-precipitating (HTPP), artificial aging (T6), retrogression and re-aging (RRA). The annealing heat treatment was performed for 2 hours at 500°C and samples were cooled in the furnace. In the artificial aging (T6) process, after the samples were solution treated for 2 hours at 500°C, they were quenched at room temperature and aged for 24 hours at 120°C. In the retrogression and re-aging process, samples were solution treated for 1 hour at 220°C after the T6 process and then re-aged for 24 hours at 120°C. In the high temperature pre-precipitating, pre-precipitates were formed for 30 minutes at 450°C and then, it was aged for 24 hours at 120°C. All samples were characterized through the scanning electron microscope (SEM + EDS), hardness measurements and X-ray difraction (XRD) techniques. At the end of experimental studies, SEM and EDS examinations XRD results revealed that η (MgZn 2 ) phase formed in the microstructure following the HTTP, RRA and T6 heat treatment processes. As a result of the fatigue tests, the highest fatigue strength was measured in samples treated with artificial aging (T6), the lowest fatigue strength was measured in the annealed (O) samples.

Investigation of the Effect of Different Heat Treatments on Wear Behavior of AA7075 Alloy

“…• C for 24 h [11]. The aged samples are subjected to standard metallographic processes for characterization studies and were etched with 2 ml HF, 90 ml distilled water, 5 ml HNO 3 and 3 ml HCl solution for 50-60 s. Etched samples are examined through SEM+EDS, XRD, and hardness measurements.…”

“…• C for 24 h ageing process [7]. At the end of the process, since corrosion sensitivity of the alloy increases, T73 heat treatment is developed to increase corrosion resistances of these types of alloys.…”

The Effect of Ageing Temperature in T6 Heat Treatment on Mechanical Properties of AA7075

“…In some previous studies, it was reported that different phases such as Al 7 Cu 2 Fe and Al 2 CuMg formed in the structure in addition to MgZn 2 precipitates [8,10]. In another study, it was noted that it is not possible to say that these precipitate phases have formed during the ageing treatment [11]. Figure 2b shows that the hardness values of the alloys, aged at different ageing temperatures for 24 h, increase by the increasing ageing temperature.…”

An Overview on Forming Process and Heat Treatments For Heat Treatable Aluminium Alloy

“…A quenching rate above the critical quenching rate of the work piece material was seen to be essential in order to avoid the generation of coarse precipitates on the grain boundaries, which diminishes the artificial ageing response of the work piece material. Furthermore, many researchers have selected water as the quenching medium and artificial ageing process as the further process of gaining the mechanical strength and hardness because water is cheap, readily available and nontoxic [30].…”