Improved structural uniformity and specific strength of commercially pure aluminum through variable temperature multi axial forging: Finite element analysis and experimental study

Abstract

Multi axial forging (MAF) is a forging-based severe plastic deformation (SPD) technique which is prominently used to refine grain structure and improve the strength of the material. While the advantages of MAF lie in its simple tool design and ability to process bulk materials, the main limitation is the inhomogeneity in the generated microstructure across the cross-section at initial passes. Increasing the number of MAF passes may partially help to solve the problem, but arbitrary increase in the number of passes may lead to redundant increase in manufacturing cost and time. The current work proposes a manufacturing strategy for MAF to achieve homogeneous microstructure with uniform grain refinement by using reduced number of MAF passes. To achieve structural uniformity within fewer MAF passes, a controlled thermo-mechanical based optimum MAF process strategy is developed on a commercial pure Al through the finite element analysis (FEA) simulation and the same is validated experimentally. The manufacturing strategy resulted significant grain refinement via simultaneous action of continuous dynamic recrystallization and geometric dynamic recrystallization with microstructural homogeneity which caused a significant improvement in tensile properties (more than two times than the base) with considerable ductility (more than 25%) and isotropy property across the thickness. The scientific knowhow has been established via processing–structure–property correlation-ship.

Keywords

• Multi-axial forging (MAF)
• Finite element analysis (FEA)
• Microstructure
• Electron backscatter diffraction (EBSD)
• Pure aluminum