Microstructure and Mechanical Properties of 6061 Aluminum Alloy Processed by Multi-Pass ECAE at Room Temperature

Abstract

In order to investigate effect of equal channel angular extrusion (ECAE) on microstructure and mechanical properties of annealed and solution-aged 6061 aluminum alloys, continuous ECAE process was carried out by physical test and finite element methods. The results show that the grains are refined with the increase of deformation; the metal flow lines cross and shear each other to form the clear boundaries. The solution-aged Al alloy does not show a monotonic increase in surface hardness with increasing passes as the annealed Al alloy does, but reaches a maximum value after the second pass and decreases successively during next two passes, which is closely related with the dislocation multiplication, recombination and annihilation. For the annealed and solution-aged Al-6061, the peak load reaches a maximum value in the second pass and fluctuates during the additional passes, which is caused by both material properties and frictions. The simulation shows that the peak load increases slowly with increasing passes, which is not in agreement with the measured value. Therefore the finite element mode using a single constitutive equation is not suitable for simulating multi-pass ECAE processing. The constitutive relations need to amend accordingly due to great changes of the mechanical properties between different passes.