Comparative Study of Microstructure and Mechanical Properties of Al 6063 Alloy Processed by Multi Axial Forging at 77K and Cryorolling

Abstract

In the present work, commercially available Al 6063 alloy was subjected to multiaxial forging (MAF) at 77K. The evolution of ultrafine grain structure during MAF at 77k at various strain levels (∑Δɛ=1.2 and ∑Δɛ =2.4) was investigated using Optical microscopy and Transmission electron microscopy. Cryorolling was performed up to true strain 2.4 and the mechanical properties and micro structural changes were compared with MAF at 77K sample of same strain. At lower strain level (∑Δɛ=1.2), the microstructure reveals formation of dislocation cells along with sub grain structure, predominantly low angle grain boundaries. Formation of elongated sub grain structure with high angle grain boundaries through dynamic recovery was observed with increasing strain up to (∑Δɛ=2.4) at shear bands. Microstructure observed in cryorolled sample is more homogeneous with low angle grain boundaries. The improvement in mechanical properties observed in both the samples processed through CR and MAF are nearly same.