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 MgZn2 particles were detected from inside the grain and grain boundary, while some Al3Zr 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: ε ˙ = [ sinh ( 0.017 σ ) ] 4.049 exp [ 19.14 − ( 129.9 / R T ) ] . An appropriate hot extrusion temperature was determined to be 460 °C. Hot deformation (460 °C by 60%) + age treatment (120 °C) was optimized to shorten the processing method for the as-spray-deposited alloy, after which considerable properties were approached. The high strength was mainly attributed to the grain boundary strengthening and the precipitation strengthening from the nanoscale MgZn2 and Al3Zr precipitates.
Highlights
Materials and MethodsThe composition of the studied alloy was Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr (wt %). The ingots were prepared using an SFZD-5000 type environmental chamber at Haoran Co., Ltd., Jiangsu, China [23]
Mg resuEltsqiunactoiaornses g(4ra)inasnadnd(5s)e,grreesgpateiocntivineilnyg,ogtsivaensd: strength [11]
The values of n and β are from the slopes of the lines in lnε and σ, lnε and lnσ, Metals 2017, 7, 299 which thermal-mechanical heat treatment and severe plastic deformation have been developed in the past decade
Summary
The composition of the studied alloy was Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr (wt %). The ingots were prepared using an SFZD-5000 type environmental chamber at Haoran Co., Ltd., Jiangsu, China [23]. Hot deformation experiments were carried out on the Gleeble-1500 thermal simulator (Dynamic Systems Inc., Poestenkill, NY, USA); the strain rates were 0.001 s−1, 0.01 s−1, 0.1 s−1, and 1 s−1, and the deformation temperatures were 340 ◦C, 380 ◦C, 420 ◦C, and 460 ◦C, respectively. The X-ray diffraction analyses on polished discs samples were performed using a D8 Discover X-ray diffractometer (Bruker AXS Inc., Karlsruhe, Germany), with a scanning step of 8◦/min, a Cu-Kα radiation graphite monochromator filtering, a tube voltage of 40 kV, a tube current of 250 mA. Phase identification was conducted on an FEI Quanta 650 scanning electron microscopy (SEM) (FEI Company, Hillsboro, OR, USA) with an electron back-scattered diffraction (EBSD) detector. The true-stress increased with the strain rate when the sample was hot-compressed at a certain temperature, while the true-stress decreased with the deformation temperature. True stress-true strain curves of the specimens hot compressed at temperatures of 340 °C (a); 3.3.
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