Conical Scrolled Dies Optimize Material Flow and Microstructure in Friction Extrusion

A computational and experimental investigation has clarified how die face geometry governs material flow, thermomechanical history, and grain refinement during the friction extrusion of aluminum rods. Friction extrusion operates as a solid-phase manufacturing method capable of producing high-performance composites characterized by low porosity and homogeneous microstructures through industrially scalable routes. Despite these practical benefits, the specific role of die surface architecture in steering localized deformation and thermal evolution had previously remained unclear. To resolve these mechanisms, researchers evaluated five distinct die geometries using an experimentally validated smoothed particle hydrodynamics computational framework alongside electron backscatter diffraction measurements of processed AA1100 aluminum alloy in the O temper condition.

The study specifically focused on aluminum feedstocks intended for electrical grid-conductor applications, comparing a standard flat die against scrolled variants and conical scrolled variants, tested both with and without a central counterbore. Numerical simulations revealed that the conventional flat die face develops a narrow interfacial sticking zone accompanied by pronounced slip adjacent to the extrusion orifice. This localized contact behavior produces concentrated strain rate and temperature fields near the tooling surface, generating steep core-to-edge gradients in accumulated plastic strain across the processed rod profile.

Introducing scroll features to the die face fundamentally alters interfacial interaction by enlarging the effective processing zone and enhancing material mixing through promoted sticking contact. When conical face profiles are implemented, they systematically lower interfacial contact pressures and homogenize the resulting thermomechanical fields throughout the deformation zone. Consequently, combining conical taper with surface scrolls balances contact dynamics and moderates severe localized heating, establishing a more uniform deformation pathway across the entire cross-section of the feedstock.

Microstructural characterization confirmed the direct mechanical consequences of these modified deformation histories on dynamic recrystallization behavior. Electron backscatter diffraction showed that the conical scrolled die and the conical scrolled die with a counterbore produced the finest dynamically recrystallized grains among all examined configurations. By correlating these microstructural observations with localized thermomechanical conditions, the authors established a quantitative Zener-Hollomon parameter-grain size relationship that offers a physics-based framework for designing future friction extrusion dies and process parameters.

Subject of Research: Influence of die geometry on friction extrusion mechanics and microstructure

Article Title: Influence of die face geometry on material flow, thermomechanical history, and microstructure in friction extrusion

Article References: Li, L., Das, H., Reza-E-Rabby, M., Shukla, S., Nittala, A. K., Soulami, A., & Kappagantula, K. S. (2026). Influence of die face geometry on material flow, thermomechanical history, and microstructure in friction extrusion. npj Advanced Manufacturing. https://doi.org/10.1038/s44334-026-00122-8

Image Credits: AI Generated

DOI: 10.1038/s44334-026-00122-8

Keywords: friction extrusion, die geometry, material flow, thermomechanical history, microstructure, AA1100, aluminum alloy, smoothed particle hydrodynamics, electron backscatter diffraction, dynamic recrystallization, grain refinement, Zener-Hollomon parameter, solid-phase processing, grid conductors, conical scrolled die, interfacial sticking, plastic strain