Microstructure evolution and mechanical properties of as-annealed and solution treated Al-Cu-Li alloy 2195 under dynamic compression

Abstract

The application prospect of 2195 alloy in aerospace structure parts has received widespread attention. The high strain rate forming combined with heat treatment process is a potential way to produce the high performance Al-Cu-Li alloy parts. In this work, the mechanical properties and microstructure evolution of the as-annealed and solution treated 2195 alloy specimens under dynamic compression were studied and compared. The dynamic compression tests were performed at the strain rates of 1400 s −1 , 2200 s −1 , 3400 s −1 , and 4500 s −1 by split Hopkinson pressure bar . The results indicate that the mechanical properties of the two kinds of heat-treated specimens have been improved by dynamic compression, an increase of 59.7 % and 63.1 % of hardness respectively. The main strengthening mechanisms of the specimen under dynamic compression conditions are fine grain strengthening, dislocation strengthening, and low angle grain boundaries strengthening , which differs depending on the heat-treated state and the strain rate . Besides, it is found that the stable-end orientation of grain rotation in the two kinds of heat-treated specimens after dynamic compression is <110 > //CD (CD: compression direction). Different from the as-annealed specimen, the solution treated specimen shows insufficient grain rotation behavior. The mechanism of insufficient grain rotation is revealed by the Schmid factor . The Schmid factor of as-annealed specimen increases by 7.5 % than that of solution treated specimen. The lower Schmid factor makes the plastic deformation resistance of solution treated specimen higher, which contributes to the insufficient grain roration behavior.