Superplastic Al-Cu-Li-Mg-Zr alloys

Abstract

Listen

Translate article

Superplastic properties have been developed in Al-Cu-Li-Mg-Zr alloys. The alloys have low Zr levels (≤0.2 wt pct) and are experimental compositions that were originally designed as low-density, highmodulus, and high strength alloys for room temperature, aerospace structural applications. The alloys have been manufactured both by an ingot metallurgy (IM) route and a powder metallurgy (PM) route involving rapid solidification processing. After conventional manufacturing, the alloys are not superplastic but require further thermomechanical processing. The microstructural changes that occur during this processing are described. Superplastic properties have been evaluated as a function of temperature, strain rate, and processing history. Prior to thermomechanical processing, the alloys have elevated-temperature ductilities of 100 to 200 pct, strain rate sensitivities of about 0.25, and activation energies corresponding to lattice diffusion. After thermomechanical processing, the alloys have ductilities of 500 to 1000 pct, strain rate sensitivities of about 0.4, and activation energies corresponding to grain boundary diffusion. In addition, room temperature properties have been measured in the solution-treated and peak aged (T6) condition for all the alloys and comparison is made with other commercial, non-Li containing, superplastic alloys. Particular emphasis is placed on properties of interest in aerospace applications such as specific modulus, specific strength, and a buckling failure criterion.