Experimental quantification of “hardenability” of 2195 and 2050 Al-Li alloys by using cold-rolled sheets

Abstract

To effectively and intuitively evaluate the “hardenability” during the design of new heat-treatable Al alloys, an experimental evaluation method by using cold-rolled thin sheets was proposed, which combined end-quenching with tensile test after aging, and eliminated the effect of different original structure of thick plate through-thickness. The “hardenability” of 2050 and 2195 Al-Li alloys was then intuitively characterized by their strength lowering as a function of distance away from the quenching end after T8-aging following end-quenching. As the distance is increased, the strength of the 2050 Al-Li alloy lowers more slowly than that of the 2195 Al-Li alloy, indicating a better “hardenability” of the 2050 Al-Li alloy. At the location with a certain distance away from the quenching end, in addition to the Cu-rich secondary phases at the grain boundary, lenticular-shaped Cu-containing secondary phases also form within grains during the end quenching process, which impede the precipitation of T1 (Al2CuLi) phase at the same local location during the following aging process. More importantly, the number of the intra-granular lenticular-shaped phases in the 2195 Al-Li alloy is much more than that in the 2050 Al-Li alloy, which contributes to a less “hardenability” of the 2195 Al-Li alloy.