Grain refinement in coarse-grained 7475 Al alloy during severe hot forging

Abstract

Grain refinement taking place in a coarse-grained 7475 Al alloy was studied in multidirectional compression at 490°C and at a strain rate of 3 × 10−4 s−1. The integrated flow curve displays significant work softening just after yielding and an apparent steady-state plastic flow at high strains. The structural changes are characterized by the development of deformation or microshear bands in coarse-grain interiors, followed by homogeneous evolution of new grains at high strains. The new grains are considered to be developed by a kind of continuous reaction through grain fragmentation that is similar to continuous dynamic recrystallization (cDRX). The mechanism of fine grain production and the factors controlling grain refinement during hot multidirectional deformation are discussed in detail.