Tribological Considerations of Recycled Aluminum Chips in Strain-Gradient Solid-State Consolidations

13 pages•Published: August 6, 2026

Htet Myet Tun, Pariwat Borwornanunporn, Thit Khant Nyein, Naing Htun Htun, Dohda Kuniaki, Tatsuya Funazuka and Numpon Mahayotsanun

Abstract

Solid-state recycling has emerged as an energy-efficient alternative to conventional remelting for aluminum scrap; however, its effectiveness depends on achieving sufficient metallurgical bonding between oxide-covered aluminum chips during consolidation. In this study, AA6063 aluminum chips were consolidated using a multi-stage billet packing technique followed by hot extrusion through a modular die system incorporating normal and strain gradient feeder geometries. The consolidated products were evaluated by optical microscopy and tensile testing to investigate the influence of material flow on consolidation behavior. Microstructural observations showed that hot extrusion effectively eliminated most of the large packing voids, although localized oxide-rich interfaces and residual chip boundaries remained within the recycled material. Tensile testing demonstrated that the recycled chip billet achieved an ultimate tensile strength comparable to that of a conventional cast billet while exhibiting a higher yield strength, indicating effective solid-state bonding during extrusion. The observed microstructural evolution and mechanical response were interpreted from a tribological perspective, highlighting the role of friction and interfacial shear in oxide fragmentation and chip-to-chip bonding. The proposed strain-gradient feeder provides a practical approach for enhancing localized deformation and offers a promising die-design strategy for improving the consolidation efficiency and performance of solid-state recycled aluminum.

Keyphrases: aluminum packing, aluminum recycling, hot extrusion, strain gradient, tribology

In: Numpon Mahayotsanun (editor). Proceedings of The 11th International Conference on Tribology in Manufacturing Processes & Advanced Surface Engineering, vol 4, pages 138-150.

Links:	https://easychair.org/publications/paper/SzLr
	https://doi.org/10.29007/gtb4

BibTeX entry

@inproceedings{ICTMP2026:Tribological_Considerations_Recycled_Aluminum,
  author    = {Htet Myet Tun and Pariwat Borwornanunporn and Thit Khant Nyein and Naing Htun Htun and Dohda Kuniaki and Tatsuya Funazuka and Numpon Mahayotsanun},
  title     = {Tribological Considerations of Recycled Aluminum Chips in Strain-Gradient Solid-State Consolidations},
  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/SzLr},
  doi       = {10.29007/gtb4},
  pages     = {138-150},
  year      = {2026}}

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