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Highly Conductive Al/Al Interfaces in Ultrafine Grained Al Compact Prepared by Low Oxygen Powder Metallurgy Technique
Dasom Kim1,2, Yusuke Hirayama2, Zheng Liu3
1Department of Materials Process Engineering, Nagoya University, 1 Furocho, Chikusa, Nagoya 464-8603, Japan.
Nanomaterials (Basel, Switzerland)
|May 5, 2021
Summary
A novel low oxygen powder metallurgy method creates dense, ultrafine-grained aluminum (Al) with exceptional hardness and electrical conductivity. Microstructure control via annealing enhances both strength and elongation for advanced material applications.
Area of Science:
- Materials Science
- Metallurgy
- Nanotechnology
Background:
- Powder metallurgy (PM) is crucial for advanced materials.
- Achieving dense, ultrafine-grained (UFG) structures in aluminum (Al) compacts at low temperatures remains a challenge.
- Controlling grain boundaries is key to optimizing mechanical properties.
Purpose of the Study:
- To develop a low-temperature powder metallurgy technique for producing dense UFG Al compacts.
- To investigate the microstructural characteristics and properties of the prepared UFG Al.
- To explore methods for enhancing the mechanical performance of UFG Al.
Main Methods:
- Preparation of Al nanopowder using low oxygen induction thermal plasma.
- Low-temperature (423 K) powder metallurgy via local surface bonding under low oxygen conditions.
- Microstructural analysis using transmission electron microscopy (TEM).
- Mechanical property testing including Vickers hardness and small punch tests.
- Annealing treatment for microstructure modification.
Main Results:
- Successfully prepared full-dense UFG Al compacts with an average grain size of 160 nm.
- Atomic-level analysis revealed minimal oxide layers at Al/Al interfaces (grain boundaries).
- Achieved high electrical conductivity (3.5 × 10^7 S/m), comparable to cast Al.
- Exhibited significantly enhanced Vickers hardness (1078 MPa), approximately 8 times that of cast Al, consistent with the Hall-Petch law.
- As-sintered compact showed premature fracture; annealing improved ultimate strength to 175 MPa and elongation to 24% by optimizing grain boundaries.
Conclusions:
- The low oxygen powder metallurgy technique enables the fabrication of high-performance UFG Al at low temperatures.
- The UFG Al compact demonstrates excellent electrical conductivity and superior hardness.
- Microstructure control through annealing is effective in achieving a desirable balance of strength and ductility.
- This method offers a promising route for producing advanced aluminum materials with tailored properties.
