Comparison of torsion and compression constitutive analyses for elevated temperature deformation of Al–Li–Cu–Mn alloy

Experimental alloy 2090 (Al – 2.1Li – 2.6Cu – 0.4Mn) was deformed in torsion and compression at temperatures T=300, 400, and 500°C and strain rates ε̇=10^–2 to 10 s^–1. The torsion and compression results were analysed using equation A(sinh ασ)ⁿ=Z=ε̇ exp(Q_HW/RT), where Z is the Zener – Hollomon parameter. The variation of stress exponent n, Arrhenius slope s, and activation energy Q_HW were calculated with variation of the stress multiplier a from 0.01 to 0.08 MPa^–1. The change of α caused the stress exponent to decrease at a declining rate and Arrhenius slope s to increase linearly, thus causing the activation energy Q_HW to become stable above α=0.04 MPa^–1. The two experimental test techniques gave very similar flow stresses and constitutive constants. At α=0.052 MPa^–1 activation energy values showed reasonable consistency with other age hardenable aluminum alloys. The compression tests were also analysed using the power law expression ε̇ exp(Q′_HW/RT)=Z=A″σ^n′.