Effect of cooling aging on microstructure and mechanical properties of an Al–Zn–Mg–Cu alloy

Comparison of microstructure and mechanical properties of TIG and laser welding joints of a new Al–Zn–Mg–Cu alloy

“…The biggest difference of the two thermal cycles is the heating and cooling rate, the value of the TIG joint is about 114°C/s and 19°C/s, while it is about 4000°C/s and 432°C/s for the laser joint. According to the studies of other authors, the critical cooling rate after the solution treatment to suppress the harmful precipitation reactions of Al-Zn-Mg-Cu alloys that have the similar composition with ours is about 100-300°C/s, and the microhardness is decreasing with the decreasing cooling rate due to forming of more harmful precipitates that have undesirable strengthening effect but consume numerous alloying elements [32][33][34][35]. So the dissolution zone of laser joint can be thought to undergo the perfect quenching without any harmful precipitates dissolving out during the cooling stage of welding, and plenty of GPI zones with desirable strengthening effect can precipitate out during storing at room temperature because of the high degree of supersaturation, as shown in Fig.…”

Effects of pre-treatments on aging precipitates and corrosion resistance of a creep-aged Al–Zn–Mg–Cu alloy

“…Generally, the mechanical properties and corrosion resistance of Al-Zn-Mg-Cu alloys are closely related to microstructures, which are greatly affected by the thermo-mechanical processing [10][11][12]. In the past, some investigations have been carried out to study the relationships between the heat treatments, microstructural evolution and properties of Al-Zn-Mg-Cu alloys [13][14][15][16][17][18][19][20][21][22][23][24]. Liu et al [13] found that the cooling aging treatment can improve the mechanical properties and corrosion resistance of Al-8.35Zn-2.5Mg-2.25Cu alloy.…”

“…In the past, some investigations have been carried out to study the relationships between the heat treatments, microstructural evolution and properties of Al-Zn-Mg-Cu alloys [13][14][15][16][17][18][19][20][21][22][23][24]. Liu et al [13] found that the cooling aging treatment can improve the mechanical properties and corrosion resistance of Al-8.35Zn-2.5Mg-2.25Cu alloy. Han et al [14] studied the effects of pre-stretching and aging on the microstructure, strength and fracture toughness of 7050 aluminum alloy, and found that the retrogression and re-aging (RRA) provides an optimum combination of the strength and fracture toughness, which improves the fracture toughness by 17% without sacrificing the strength.…”

Effect of quenching parameters on the mechanical properties of the 7A04 aluminium alloy

“…The microhardness, room-temperature mechanical properties, and phase composition of the alloys were determined after different steps of aging, and the strengthening mechanism was discussed. Y. Lin et al 7 studied the effect of non-isothermal cooling aging on the microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy, and the tensile strength, yield strength and conductivity were increased 2.9 %, 8.1 % and 8.3 % compared to that of the T6 treatment, respectively. T. Marlaud et al 8 studied the influence of alloy composition and heat treatment on the precipitate composition.…”