Experimental and Theoretical Studies of the Hot Tearing Behavior of Al- x Zn-2Mg-2Cu Alloys
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HOT tearing is one of the major defects of aluminum alloys that limits their production and causes rejects during direct chill (DC) casting.[1] It often occurs during later solidification stages corresponding to the fraction solids of greater than 0.9 and formation of a continuous grain network.[2] Several factors increase the probability of hot tearing, including high casting speeds, large billet diameters, and high cooling rates.[3–6] The importance of the alloy composition has also been emphasized. In the last decades, significant efforts have been made to study the effect of the composition of aluminum alloys on their hot tearing behavior. The hot tearing behavior of several binary Al alloys (such as Al-Si, Al-Cu, Al-Mg, Al-Fe, Al-Mn, and Al-Zn ones) has been investigated and summarized in detail by Eskin et al.[7] It is widely known that the addition of alloying elements to pure aluminum
Y. LI, X. GAO, Z.R. ZHANG, W.L. XIAO, H.X. LI, and J.S. ZHANG are with the State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, China. Contact e-mail: [email protected] Q. DU is with the SINTEF Materials and Chemistry, Trondheim, Norway. L. KATGERMAN is with the Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands. L.Z. ZHUANG is with the State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing and also with the Tata Steel, 1970 CA, Ijmuiden, The Netherlands. Contact email: [email protected] Manuscript submitted May 6, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
broadens its freezing range and increases its hot tearing susceptibility, while further alloying leads to the formation of a large amount of eutectics, which reduce the hot tearing probability of the studied material. Hence, maximum cracking susceptibility occurs at a certain alloy composition. The variation tendency is called the lambda-type curve.[2,7,8] Moreover, the hot tearing behavior of ternary Al-Cu-Si, Al-Cu-Mg, Al-Fe-Si, and Al-Si-Mg alloys has also been summarized by Eskin et al.[7] The classical patterns of binary systems were also observed in these ternary alloys, i.e., there is a certain alloy composition at which the hot cracking susceptibility will reach a maximum value. Recently, Easton et al.[8] investigated the hot tearing susceptibility of ternary Al-Si-Mg alloys with refined grains via direct crack observations, load measurements, and predictions made using a modified Rappaz–Drezet–Gremaud (RDG) model. A peak value was observed at Si and Mg contents of approximately 0.2 and 0.15 wt pct, respectively, although the composition was slightly lower than that obtained for non-refined Al-Si-Mg alloys.[8] Al-Zn-Mg-Cu series aluminum alloys have a great potential for structural parts in the aeronautics industry. Currently, new alloys are being developed to further improve their properties such as strength, damage tolerance, and corrosion resistance by adjusting the rat
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