Deformation behavior, constitutive modeling and microstructure evolution of 2195 Al-Li alloy deformed at high strain rates and cryogenic temperatures

Abstract

High-speed and cryogenic-temperature forming technologies have exhibited great potential for fabricating advanced Al-Li alloy components for aircraft due to their ability to enhance materials’ formability. However, there remains an urgent need to study the high-accuracy constitutive model and complex deformation mechanism of Al-Li alloys deformed at high strain rates and cryogenic temperatures. In this study, the flow stress behavior and microstructure evolution of 2195 Al-Li alloy were investigated over a wide stain rate range (from 2000 s−1 to 5000 s−1) and temperature range (from 298 K to 123 K). The flow stress increases by ∼ 32% at 2000 s−1 and ∼ 37% at 5000 s−1 as the deformation temperature drops from 298 K to 123 K, but only increases by ∼ 4% at 298 K and ∼ 8% at 123 K as the strain rate increases from 2000 s−1 to 5000 s−1. At the high strain rate of 5000 s−1, the T1 phases exhibit bending (at 298 K) and fracturing (at 123 K), with increased lattice distortion and substructure generation around the intersections of T1 phases. A new constitutive model (g-Johnson-Cook model) is developed, which shows a higher accuracy than both the Arrhenius model and Johnson-Cook model in describing the deformation behavior.

Keywords

• Al-Li alloy
• High-speed deformation
• Low temperature
• Flow stress behavior
• Constitutive equation
• Deformation mechanism