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All Journal Rotasi Teknika: Jurnal Sains dan Teknologi Emerging Science Journal Civil Engineering Journal Abdi Masya
Eko Surojo
Universitas Sebelas Maret Surakarta
Agriculture, Biological Sciences & Forestry Humanities Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Electrical & Electronics Engineering Engineering Environmental Science Industrial & Manufacturing Engineering Mechanical Engineering Other

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Journal : Civil Engineering Journal

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Enhancing AA6061–Bottom Ash Composites: Role of Heat Treatment on Properties and Dimensional Stability Seputro, Harjo; Bintoro, Sefrian R.; Ariawan, Dody; Surojo, Eko; Triyono
Civil Engineering Journal Vol. 11 No. 11 (2025): November
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-11-023

Abstract

Aluminum matrix composites (AMCs) reinforced with industrial by-products have attracted attention as lightweight, sustainable materials, yet most research has focused on fly ash. The higher density of bottom ash compared to fly ash makes bottom ash suitable for use as reinforcement in AMC. This study investigates the combined effect of BA reinforcement (0, 3, and 6 wt%) and T6 heat treatment (aging at 175, 200, and 225 °C) on the microstructure, mechanical performance, thermal expansion, and dimensional stability of AA6061 composites. Mechanical testing, thermomechanical analysis (TMA), and coordinate measuring machine (CMM) evaluations were conducted to establish correlations between microstructure and macroscopic reliability. The results show that aging plays a decisive role in strengthening and stabilizing the alloy. The unreinforced AA6061 achieved peak hardness (69.43 BHN) and tensile strength (274.60 MPa) at 200 °C, but exhibited the largest distortion due to high thermal expansion. BA addition significantly reduced the mean coefficient of thermal expansion, with the 3 wt% BA composite aged at 200 °C demonstrating the most balanced behavior: stable CTE response, minimal distortion (0.1–0.4 mm²), and improved mechanical reliability. In contrast, 6 wt% BA composites, despite their lowest mean CTE (≈25 ppm/K), suffered from local instabilities due to particle agglomeration and porosity, leading to reduced toughness and higher geometric irregularities. Overall, this work highlights the novelty of employing BA as a sustainable reinforcement distinct from fly ash, showing that moderate BA addition coupled with optimized heat treatment can enhance dimensional stability and mechanical performance. The findings provide new insights into the design of cost-effective, environmentally friendly AMCs for structural applications.
Effect of Cu and SiO₂ on a Remelted-Recycled Piston Alloy Under Vertical Centrifugal Casting Conditions Triyono, Teguh; Surojo, Eko; Prabowo, Aditya Rio; Triyono, Triyono; Djordjevic, Branislav; Carvalho, Hermes; Adie, Prayoga Wira; Sholehuddin, Muhammad Ilham
Civil Engineering Journal Vol. 12 No. 1 (2026): January
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2026-012-01-020

Abstract

Functionally graded aluminum matrices produced by means of centrifugal casting offer a route to location-specific properties, yet sustainable feedstocks and dual-density reinforcements are less well explored. In this work, we evaluate vertical centrifugal casting (VCC) of a remelted, recycled piston alloy reinforced with silica (SiO₂) and copper (Cu) particulates selected for their contrasting densities relative to the matrix. Castings were produced at 1000 rpm for 5 minutes using a 500 °C preheated mold and an 800 °C pour temperature. Cu was added at 1–4 wt.% and SiO₂ was added at 0–9 wt.%. Bulk density/porosity measurements, Vickers hardness testing, and optical/SEM microstructural analysis were employed to characterize the resulting gradients. The density increased with the radial distance from the rotation axis, accompanied by a monotonic decrease in porosity, consistent with centrifugal separation. Microstructurally, SiO₂ concentrated toward the inner region near the rotation center; in comparison, Cu was enriched at the outer periphery. Correspondingly, hardness exhibited a spatial gradient: SiO₂-reinforced zones were hardest near the inner region, whereas Cu-rich outer zones were hardest at the external rim. These results demonstrate that VCC of a recycled Al–Si feedstock can be used to reliably tailor its microstructure and properties through density-driven particle segregation, enabling controllable, bidirectional functional grading using environmentally friendly starting materials.
Co-Authors Adie, Prayoga Wira Aditya Rio Prabowo Agiel, Raiddin Muhamad Agus Suprihanto Akbar, Hammar Ilham Anwar Nurharyanto Bambang Margono Bintoro, Sefrian R. Carvalho, Hermes Chamim, Moch. Djordjevic, Branislav Dody Ariawan Halim, Dimas Ardiansyah Harjo Seputro, Harjo Ilham Habibi, Ilham Majid, Faishal M. Nurul Muhayat Pramudi, Ganjar Raharjo, Wijang W. Sholehuddin, Muhammad Ilham Sukmaji Indro Cahyono, Sukmaji Indro Teguh Triyono Triyono Triyono Triyono