Hot Deformation Behavior of a Spray-Deposited Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr Alloy

Abstract

Abstract:Metallic materials have a significant number of applications, among which Al alloys have drawn people's attention due to their low density and high strength. High-strength Al-based alloys, such as 7XXX Al alloys, contain many alloying elements and with high concentration, whose microstructures present casting voids, segregation, dendrites, etc. In this work, a spray deposition method was employed to fabricate an Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr (wt %) alloy with fine structure. The hot deformation behavior of the studied alloy was investigated using a Gleeble 1500 thermal simulator and electron microscopes. The microstructure evolution, variation in the properties, and precipitation behavior were systematically investigated to explore a short process producing an alloy with high property values. The results revealed that the MgZn 2 particles were detected from inside the grain and grain boundary, while some Al 3 Zr particles were inside the grain. An Arrhenius equation was employed to describe the relationship between the flow stress and the strain rate, and the established constitutive equation was that: Figure 7 gives the hardness variations of the hot compressed samples aged at 120 • C fo durations. For the samples after being hot-compressed at strain rates of 1 s −1 and 0.001 s −1 , present the same trend. The initial hardness of compressed samples increased with the hot de temperature. The hardness of the hot-compressed samples increased with the aging time, a kept constant as they were aging at certain temperatures for 15 h.Metals 2017, 7, 299 deformation temperature. The hardness of the hot-compressed samples increased with the and almost kept constant as they were aging at certain temperatures for 15 h. Discussion Constitutive EquationThe constitutive relationships were used to describe the hot deformation behavior. Som are employed to reveal the hot deformation behavior, in which one of the most extended v the hot working constitutive equation is as follows [24]:where ε is the strain rate; A is a material constant which is independent of temperature true stress; Q is the activation energy; R is the gas constant (8.31); and T is the absolute tem (K). At low stress lever (ασ < 0.8):At high stress lever (ασ > 1.2):(σ) σ n F  , β and n are the material constants, α = β/n. Substituting Equations (2) and (3) (4) and (5), respectively, gives:The values of n and β are from the slopes of the lines in ln ε and σ, lnε and ln σ , Discussion Constitutive EquationThe constitutive relationships were used to describe the hot deformation behavior. Som are employed to reveal the hot deformation behavior, in which one of the most extended v the hot working constitutive equation is as follows [24]:where .ε is the strain rate; A is a material constant which is independent of temperature; σ is stress; Q is the activation energy; R is the gas constant (8.31); and T is the absolute tempera At low stress lever (ασ < 0.8):At high stress lever (ασ > 1.2): F(σ) = σ n , β and n are the material constants, α = β/n. Substit...

Hot Extrusion Enhanced Homogenization of Microstructure in a Spray Deposition Aluminum Alloy

“…In this work, the solidification rate was estimated as 10 3 -10 4 °C/s based on the parameters listed in Table 1, which provided sufficient cooling rate to solidify the melt within one second. The extreme fast cooling rate forced the crystallization of partial melt to occurr directly from the liquid state without generating dendrites; similar result was found in previous reports [4,5,9]. As a result, equiaxed grains with average size 42 ± 1.2 μm were obtained after the spray deposition, as illustrated in Figure 1.…”

“…Temperatures ranging from 380 to 460 • C were proved to be the optimal deformation window according to our previous work, in which, the as-deposited alloy 7055 could be directly deformed without being subjected to pre-heat treatment [9]. In this article, we introduced isothermal compression to evaluate the effects of deformation temperatures (340 to 460 • C) and strain rates (0.001 and 1.0 s −1 ) on the homogeneity of the microstructure.…”

“…With the assistance of spray deposition method, the aluminum alloy with high alloying could be produced with segregation being controlled at the micro-scale level. In this situation, the as-deposited alloy could be deformed under controllable parameters without being subjected to pre-homogenization heat treatment [9]. Recently, significant efforts have been made to study the hot deformation behaviors [10][11][12][13][14][15], quenching sensitivity [16][17][18][19], corrosion resistance [20-23] and weldability [24-29] of 7055.…”

“…The XRD (X-ray diffraction) of spray-deposition 7055 aluminum alloy showing the existed phases[9] (Metals, 2017).…”

“…The SEM (scanning electron microscope) images of spray-deposition 7055 at different magnification[9] (Metals, 2017): (a) 1000x; (b) 2000x.…”