Tensile mechanical properties, constitutive parameters and fracture characteristics of an as-cast AA7050 alloy in the near-solidus temperature regime

Abstract

The knowledge on constitutive mechanical behavior at the temperatures close to the solidus is essential for predicting high-temperature deformation and fracture, e.g. cold and hot cracking of aluminum alloys. In this work we studied the tensile mechanical properties of an as-cast AA7050 alloy in a near-solidus temperature regime. Tensile tests were carried out using Gleeble-3800 TM system at temperatures from 400 to 465 °C and at strain rates from 0.0005 to 0.05 s -1 . The resultsshow that the strength decreases with increasing temperature and decreasing strain rate.Meanwhile, ductility decreases with the increase of temperature and strain rate. The constitutive parameters were extracted by fitting the test data to the extended-Ludwik and creep-law equations. The parameters for the extended-Ludwik equation are continuous with the values from a lower temperature regime obtained earlier, while the parameters for the creep-law equation are comparable with those obtained on other 7XXX aluminum alloys. We observed a change in fracture mode at 450 °C; from ductile transgranular to intergranular. This temperature coincides with the discontinuity point of the temperature-ductility slope. On the fracture surface of a sample that was deformed at 465 °C with a strain rate of 0.0005 s -1 , we observed features characteristic of micro-superplasticity. Considering the test conditions, viscous flows of incipient melt or liquid-like substances are suggested to be responsible for the formation of this feature.2 Keywords: AA7050, near-solidus temperature, tensile mechanical behavior, constitutive parameters, fracture surface analysis.

Semi-solid Constitutive Parameters and Failure Behavior of a Cast AA7050 Alloy

“…[23,35] The constitutive parameters of an AA7050 at sub-solidus temperature were obtained in our previous work. [24] In this work, we set T merge = 410°C and T 0 = 390°C as suggested by Lalpoor et al [23] The nomenclature of each variable in the equations is shown in Table III.…”

“…[1] through [5]) show that the constitutive parameters that need to be extracted and optimized are the rheological parameters p, a 0 , a 1 , g s coal and k. Since the parameters of the solid part of the alloy (represented by creep law properties, Eqs. [7] and [8]), i.e., r 0 , _ e 0 , Q and n, were obtained in our previous work, [24] in this study we focus on obtaining the constitutive parameters for the semi-solid part of the constitutive model by utilizing the ALSIM package.…”

“…[7] and [8]), the parameters obtained in our previous work were used. [24] For the semi-solid part, we used the Al-2 wt pct Cu semi-solid database [28] as an initial guess because of its availability and its similarity to AA7050 in terms of HT susceptibility. [9] Using this combination of databases, we carried out the numerical tensile tests and then compared the value between the numerical and experimental force-displacement results.…”

“…At the moment, ALSIM only has constitutive parameters for an AA7050 alloy in the fully solid state [23] and the sub-solidus regime. [24] Hence, ALSIM is currently lacking a constitutive behavior database for the semi-solid regime of an AA7050 alloy, [20] needed for modeling HT behavior. Instead, the Al-2 wt pct Cu data are used to complete the semi-solid part of the database.…”

Precipitation Behavior and Quenching Sensitivity of a Spray Deposited Al-Zn-Mg-Cu-Zr Alloy

“…In the past decades, 7xxx series (Al-Zn-Mg-Cu) aluminum alloys exhibited an outstanding performance and attracted much interest in many industry fields, especially in the automotive and the aviation field [ 1 , 2 , 3 ], because of their high strength, high ductility, and low density [ 4 , 5 ]. The high strength makes the products strong, and the high ductility allows the products to be easily forming during the machining process, and the low density saves the energy cost and reduces the carbon emission.…”