Comparative analysis of microstructures developed in 7475-type aluminum alloyunder high-temperature equal-channel angular pressing and multidirectional forging
A comparative analysis of structural changes in the high-strength aluminum alloy 7475 subjected to equal channel angular) has been performed. It was shown thatpressing (ECAP) and multidirectional forging (MDF) at a temperature of 400 °C (~ 0,75 T mboth ECAP and MDF of the present alloy led to significant grain refinement. The main mechanism of structural changes was mainly related to the formation of deformation bands such as geometrically necessary boundaries, microshear bands which are developed in various directions and fragment initial grains leading to occurrence of “continuous” dynamic recrystallization.Comparison of schemes of ECAP and MDF at roughly the same strain values revealed the formation of similar microstructures,which were characterized by the close values of the average misorientation angles and the fractions of high-angle boundaries.It was also found that, irrespectively on the deformation scheme, the grain size developed in both ECAP and MDF obeys the common dependence (unique function) on the Zener - Hollomon parameter, Z. The features of the microstructural development in the heavily alloyed aluminum alloy during high-temperature severe plastic deformation (SPD), as well as the effects of SPD schemes on grain refinement were discussed in details.