Partially Melted Zone in Aluminum Welds

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9803589 Kou The object of this program is to better understand the formation, structure and properties of the partially melted zone formed during gas metal arc welding of aluminum alloys. Gas metal arc welds are made on an aluminum-4.5% copper alloy to examine the grain boundary structure and determine the temperature gradient and growth rate. Solute and hardness distributions are determined across grain boundaries by scanning transmission electron microscopy and nano indentation. Thermal effects are explored using pulsed gas metal arc welding to determine effect on grain boundary liquation. Benefits are expected based on the lower heat input produced by the pulsing process. Gleeble simulation of the weld structure provides controlled, known thermal cycles and nearly one dimensional heat flow to samples undergoing grain solidification. %%% Gas metal arc welding is the most widely used process for welding aluminum alloys. The research has application to the welding of aluminum structures, such as an all-aluminum automobile body, one direction pursued to reduce the weight of future automobiles. ***