Effect of Contraction Behaviors during Solidification of 7xxx Aluminum Alloys on Hot Tearing Susceptibility

Abstract:

Contraction behavior of 7xxx aluminum alloys was systematically investigated using a new device for measuring linear contraction during solidification. The effects of contraction behaviors and microstructure during solidification of three types of 7xxx series aluminum alloys on the hot tearing susceptibility were studied. It was found that the contraction behaviors of the three alloys showed extremely different shrinkage characters during solidification. The linear expansion coefficient (LEC) of 7050 and 7075 alloys shown an enormous increase from rigidity point (solid fraction is 0.69 and 0.73 respectively) to the peak value and then dropped to a constant value with the decreasing temperature. The LEC of 7022 alloy is different from the 7050 and 7075 alloys that it increases from rigidity point (solid fraction around 0.8) with a small fluctuation at the temperature little lower to the rigidity point and then they increase monotonously to the room temperature. The microstructure showed that the onset of the contraction process was the point which dendrites started coalescence. The profiles of thermal expansion coefficient of 7050 alloy were greater than the 7022’s during the solidification process, so the contraction behavior of the alloy during solidification could be used as a kind of criterion of hot tearing susceptibility.

• Periodical: Materials Science Forum (Volumes 783-786)
• Pages: 300-306
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.783-786.300
• Online since: May 2014
• Authors: Hiromi Nagaumi, Guan Xia Xue, Zheng Zheng Zhang, Yu Li Ma
• Keywords: 7XXX Aluminum Alloys, Contraction Behavior, Hot Tearing Susceptibility, Solidification

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