Process-Microstructure-Property Correlation in Vacuum Sintered Al-Al2O3 Functionally Graded Pellets

Authors

  • Satyasaibaba Pitta Department of Mechanical Engineering, University College of Engineering, JNTUK, Kakinada-533003, India.
  • Ranga Janardhana Ginka Department of Mechanical Engineering, Jawaharlal Nehru Technological University Anantapur, Anantapuramu-515002, India. https://orcid.org/0000-0002-1451-792X
  • Balakrishna Bhanavathu Department of Mechanical Engineering, University College of Engineering, JNTUK, Kakinada-533003, India.

DOI:

https://doi.org/10.22401/anjs.29.3.4029

Keywords:

Aluminum , Alumina, Functionally graded material, Metallurgical characterization

Abstract

Aluminum-alumina (Al-Al2O3) functionally graded materials are attractive for components requiring a compliant metallic base and a hard ceramic rich surface. However, their performance is strongly limited by transition layer porosity and incomplete densification during low temperature powder metallurgy. In this study, a five-layer Al-Al2O3 graded pellet was fabricated by sequential powder stacking, planetary ball milling of mixed layers, low pressure uniaxial compaction at 20 MPa, and vacuum solid-state sintering at 580 °C. The designed solid phase volume fractions from bottom to top were 100/0, 75/25, 50/50, 25/75, and 0/100 Al/Al2O3, with a nominal pellet diameter of 20 mm and layer thickness of 2 mm. Particle size distribution, X-ray diffraction (XRD), scanning electron microscopy, image-based porosity, Archimedes bulk density, Vickers microhardness, compression, flexural, and sliding wear tests were used to establish the process-microstructure-property relationship. XRD confirmed face centered cubic aluminum and α-Al2O3 as the dominant crystalline phases, with no obvious crystalline reaction products after sintering. The pellet retained macroscopic integrity, but porosity varied non-linearly across the gradient, reaching 9.12%, 15.26%, 10.26%, 16.23%, and 15.36% from Layers 1 to 5. The bulk density measured was 2.88 g·cm-3. The microhardness of the Al layer was raised significantly with the Al2O3 layer, from 44.6 HV0.1 to 703.0 HV0.1. In addition, the specimen exhibited Compressive strength of 138.24 MPa, Flexural strength of 34.03 MPa and Mean Coefficient of friction of 0.278 ± 0.030. The results indicate that low pressure powder stacking can produce a stable Al-Al2O3 hardness gradient but the main limitation, which needs improvement, is the porosity in the transition layer.

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Published

2026-09-15

Issue

Vol. 29 No. 3 (2026): September 2026

Section

Physics

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Copyright (c) 2026 Satyasaibaba Pitta, Ranga Janardhana Ginka, Balakrishna Bhanavathu

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This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite

(1)
Pitta, S.; Janardhana Ginka, R. .; Bhanavathu, B. . Process-Microstructure-Property Correlation in Vacuum Sintered Al-Al2O3 Functionally Graded Pellets. Al-Nahrain J. Sci. 2026, 29 (3), 145-163. https://doi.org/10.22401/anjs.29.3.4029.