Papers by Keyword: Al-Zn-Mg Alloy

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Authors: Prasanta Kumar Rout, K.S. Ghosh
Abstract: Artificial aging behaviour of a 7017 Al-Zn-Mg alloy was studied by hardness measurement. The electrochemical behaviour of various alloy tempers, such as under-, peak-, and over-aged, have been evaluated by measuring variation of open circuit potential (OCP) with time and potentiodynamic polarization study in different environments. All the alloy tempers were tested in 3.5 wt. % NaCl solution at neutral (pH 7), at acidic (pH 1) and at alkaline (pH 12) conditions. It has been observed that the OCP values of the alloy tempers shifted toward noble direction with the increase of aging time in 3.5 wt. % NaCl solution. The polarization curves are more or less similar in shape exhibiting only active region in neutral (pH 7) and in acidic (pH 1) conditions, but an active-passive region at alkaline (pH 12) condition. The electrochemical parameters; Ecorr, Icorr, passive potential range (Ep) and passive current (ip), obtained from potentiodyanamic polarization curves for the alloy tempers in acid, neutral and alkaline solution; depend on the alloy tempers and the pH of the solution as well. Attempts have been made to explain the observed electrochemical behaviour of the alloy tempers, which is influenced by the microstructure, presence and distribution of second phase precipitates, accessed by DSC and XRD techniques.
Authors: Manoj Kumar, Nikolay Sotirov, Christian Chimani
Abstract: High formability is required to stamp aluminium into complex structural automotive components such as the A-pillar and B-pillar. Formability of an Al-Zn-Mg (AA7xxx) alloy sheet is characterised through hot stamping a prototype part and simulating paint baking procedures. The precipitation behaviour is assessed by differential scanning calorimetry and the tensile properties measured between 350°C and 475°C over a range of strain rates from 0.01s-1 to 1s-1. Natural ageing was found to increase the hardness of the hot stamped parts due to the formation of GP zone precipitates. A simulated three step paint baking procedure produced η precipitates and resulted in a yield strength and ultimate tensile strength of 480MPa and 512MPa, respectively.
Authors: A. Dupasquier, Rafael Ferragut, M.M. Iglesias, C.E. Macchi, Mario Massazza, P. Mengucci, G. Riontino, Alberto Somoza
Authors: Tomoshi Takahashi, Toshimi Yamane, Hideki Araki, Yoritoshi Minamino, Yoshinari Miyamoto
Authors: Feng Wang, Bai Qing Xiong, Yon Gan Zhang, Hong Wei Liu, Zhi Hui Li, Xi Wu Li
Abstract: Abstract. The microstructure and mechanical properties of a metal inert gas welds in a medium strength Al-4Zn-1Mg alloy were characterized by optical microscope (OM), scanning electron microscope (SEM) and tensile tests. It is found that the joint of the alloy contained three distinctive regions, i.e. fusion zone, heat affected zone and base metal region. Extensive microhardness measurements were conducted in the weld regions of the nuggets exhibited a hardness loss in the fusion zone due to the loss of strengthening phases. Microstructural examination of the joints revealed typical eutectic structure was appeared in the heat-affected zone. Tensile properties of the joints were obtained by testing flat transverse tensile specimens, and the results indicated that tensile strength of these welds approached 83.3~84.2% of the base metal.
Authors: Keitaro Horikawa, Hiroyuki Yamada, Masahide Mutsuo, Hidetoshi Kobayashi
Abstract: Hydrogen gas evolution behaviour during deformation and fracture in Al-Zn-Mg alloys with and without copper additions was examined by using a testing machine equipped with a quadrupole mass spectrometer in an ultrahigh vacuum chamber (QMS-UHV) and by a hydrogen microprint technique (HMT). The QMS-UHV testing revealed that hydrogen gas was evolved at the moment of grain boundary fracture, in particular. This suggested that hydrogen atoms primarily dissolved were trapped at the grain boundaries before the fracture. It was also revealed that hydrogen gas evolution behaviour was changed according to the testing strain rate. The HMT also revealed that silver particles, which represented the emission sites of hydrogen, were observed mainly around the second phase inclusions and the grain boundaries.
Authors: Sanjoy Sadhukhan, Molay Kundu, Manojit Ghosh
Abstract: The heat treatable 7xxx series Al alloys (Al-Zn-Mg) show good combination of tensile properties through precipitation hardening. Similar to Al-Cu alloy minor addition of Sn in this alloy also influences its structure and properties. The hardness improves after natural ageing and further improves after duplex ageing. Duplex ageing refines the grains also. SEM-EDX results indicate that β-Sn is present in the form of precipitates. DSC results indicate that Sn suppresses the formation of GP zone and the stability of intermediate η phase is higher.
Authors: B. Bjørneklett, Øystein Grong, A.O. Kluken, O. Jensrud
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