Deformation mechanisms in ARB processed aluminium alloy AA6016 at low temperatures

The deformation behaviour of the aluminium alloy AA6016 at low temperatures was investigated in the initial state and after 4 and 8 cycles of accumulative roll bonding (ARB). Tensile tests at 25 K, 77 K, 180 K and 296 K were performed at constant strain rate 10−4 s−1. Stress relaxation experiments performed during the tensile tests were used to determine the experimental rate sensitivity λ as a function of the flow stress σ. In all cases λ (σ) is found to be linear revealing that the Cottrell-Stokes law holds. The effect of grain size on σ can be adequately described through an additive athermal stress contribution σd, which is the higher the higher the degree of pre-deformation is. Moreover, the temperature dependence of the strain rate sensitivity m(T) indicates that the rate controlling mechanism in the initial state is local single slip. The ARB states deviate from the single slip behaviour already at 25 K. The reason probably is the occurrence of additional thermally activated slip processes in the ARB states.