Influence of Degree of Deformation and Aging Time on Mechanical Properties and Microstructure of Aluminium Alloy with Zinc / Wpływ Stopnia Odkształcenia I Czasu Starzenia Na Właściwośi Mechaniczne I Mikrostrukturę Stopu Aluminium Z Cynkiem

Abstract

In order to investigate the influence of the deformation degree and aging time on the mechanical properties and microstructure of AA7050 alloy static tensile test, microhardness measurements, calorimetric analysis and observations of the microstructure in the transmission and scanning electron microscope were carried out. For study a series of cylindrical specimens with an initial diameter of about 3 mm were used. The samples were saturated at a temperature of 470° C for 1 hour and quenched in water. The samples were then subjected to deformation up to the three levels: 0%, 5% and 10%. Deformed samples was artificially aged at 120°C for 6 hours, 12 hours, 24 hours and 72 hours. The results showed that the increase in the degree of deformation caused an increase in yield strength and a decrease in ductility. The longer aging time influenced on an increase in tensile strength, yield stress and microhardness and a decrease in ductility. An analysis of the precipitates present in the material was conducted. The highest value of yield strength equal 538 MPa with elongation 9.2% were obtained for sample pre-strained to 10% and aged for 24 hours. The obtained results showed that prolongation in aging time and use of pre-strain were beneficial for precipitation processes courses, consequently, for optimal mechanical properties of alloy 7050.

AA7050 Al Alloy Hot-Forging Process for Improved Fracture Toughness Properties

“…The reason for this improvement The influence of deformation and time on the mechanical properties of 2XXX and 7XXX alloys has been investigated [30] to prove that an increase in the degree of deformation (up to 10%) causes an increase in yield strength and the decrease of tensile elongations. The reason for this improvement is widely discussed in the literature and was found to be related to the microstructure and precipitate evolution mainly formed from GP to Mg(Zn,Cu) 2 phases [31]. Moreover, some authors [30][31][32] indicate clearly that in AA7050 alloy, an HCP structure phase (a = 5.32 Å, c = 8.79 Å) nucleates on the grain boundary.…”

“…is widely discussed in the literature and was found to be related to the microstructure and precipitate evolution mainly formed from GP to Mg(Zn,Cu)2 phases [31]. Moreover, some authors [30][31][32] indicate clearly that in AA7050 alloy, an HCP structure phase (a = 5.32 Å , c = 8.79 Å ) nucleates on the grain boundary. This structure was found to be similar to that of MgZn2 with some Cu next to Mg and Zn.…”