Comparative analysis of microstructures formed in highly alloyed aluminum alloy during high-temperature equal-channel angular pressing and multidirectional forging

Abstract

A comparative analysis of structural changes in the high-strength aluminum 7475 alloy subjected to equal channel angular pressing (ECAP) and multidirectional forging (MDF) at a temperature of 400°C (~0.75 Tm) is performed. It is shown that both ECAP and MDF of the present alloy led to significant grain refinement. The main mechanism of structural changes is mainly related to the formation of deformation bands such as geometrically necessary boundaries and microshear bands, which propagate in various directions and fragment initial grains, thus developing in “continuous” dynamic recrystallization. Comparison between ECAP and MDF performed to roughly the same strain values reveals the formation of similar micro-structures, which are characterized by close values of the average misorientation angles and the fractions of high-angle boundaries. It is also found that, irrespective of the deformation scheme, the grain size developed in both ECAP and MDF obeys a common dependence (unique function) on Zener–Hollomon parameter Z. Microstructure evolution in the highly alloyed aluminum alloy during high-temperature severe plastic deformation and the effect of severe plastic deformation techniques on grain refinement are discussed in detail.