Tribo-Characteristics in Hot AA7xxx via V-Groove Friction Test

10 pages•Published: August 6, 2026

Sukunthakan Ngernbamrung, Tatsuya Funazuka, Junichi Oshima, Tomomi Shiratori and Kuniaki Dohda

Abstract

High-strength AA7075 aluminum alloys are essential for lightweight design in the aerospace and automotive sectors. However, their hot extrusion is limited by two critical tribological challenges, specifically tearing surface flaws and severe adhesive wear galling resulting from the reaction of alloying elements with traditional steel tools. These issues drastically reduce die service life and compromise product integrity. To overcome these limitations, this study investigates the hot tribological behavior of AA7xxx series alloys, varying the Zinc (Zn) and Magnesium (Mg) content, utilizing the conventional SKD61 die material with nitriding surface treatment.
The methodology employed the hot V-groove friction test, a specialized method simulating plastic working that combines extrusion and compression. The experimental protocol began with a Finite Element Method (FEM) simulation by using DEFORM-3D software. The FEM analysis was conducted at 400°C, 450°C, and 500°C with a diameter 7 x 70 mm specimen and a punch speed of 0.1 mm/s, systematically varying the shear friction coefficient from 0.1 to 1.0. The simulation established the essential calibration curve by plotting the shear friction coefficient (m) against the V-groove’s final aspect ratio (Height/Width). This curve quantifies the direct relationship between frictional condition and material deformation. This curve was subsequently used to determine the actual friction coefficients observed in the experimental tests. Subsequent experimental tests used AA7xxx specimens with various compositions of Zn and Mg and SKD61 die material with nitrided surface preparation under identical temperature conditions. The study concluded with elemental analysis of the V-groove tool surface using Electron Probe Micro Analyzer (EPMA) to quantify the adhesion of elements such as Mg, Zn, Copper (Cu), and Oxygen (O).
Based on the determination of the hot shear friction coefficient and the forming load, the conventional SKD61 die showed similar performance across varying alloy compositions. Crucially, elemental analysis of the tool surfaces demonstrated that adhesion phenomena were highly dependent on the AA7xxx composition. The EPMA quantified significant adhesion of alloying elements to the SKD61 die, with the concentration of these elements being correlated with the specific alloy composition tested. Understanding this adhesion mechanism is vital for guiding optimal die coating or lubrication strategies to prevent galling. This comprehensive tribological investigation provides critical data for optimizing AA7xxx alloy composition to minimize tool-die reactions, thereby mitigating surface flaws and extending die service life under nitriding conditions.

Keyphrases: aa7xxx alloy, adhesive wear, hot extrusion, tribology

In: Numpon Mahayotsanun (editor). Proceedings of The 11th International Conference on Tribology in Manufacturing Processes & Advanced Surface Engineering, vol 4, pages 30-39.

Links:	https://easychair.org/publications/paper/LVw5
	https://doi.org/10.29007/pj2g

BibTeX entry

@inproceedings{ICTMP2026:Tribo_Characteristics_Hot_AA7xxx,
  author    = {Sukunthakan Ngernbamrung and Tatsuya Funazuka and Junichi Oshima and Tomomi Shiratori and Kuniaki Dohda},
  title     = {Tribo-Characteristics in Hot AA7xxx via V-Groove Friction Test},
  booktitle = {Proceedings of The 11th International Conference on Tribology in Manufacturing Processes & Advanced Surface Engineering},
  editor    = {Numpon Mahayotsanun},
  series    = {EPiC Series in Technology},
  volume    = {4},
  publisher = {EasyChair},
  bibsource = {EasyChair, https://easychair.org},
  issn      = {2516-2322},
  url       = {/publications/paper/LVw5},
  doi       = {10.29007/pj2g},
  pages     = {30-39},
  year      = {2026}}

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