The effects of the reinforcement of alumina and rice husk particles on the hybrid recycled aluminium AA7075 chips composite on physical, mechanical and morphological properties

• Main Author: Kamaruddin, Nor Asmalinda
• Format: Thesis
• Language: English; English; English
• Published: 2022
• Subjects: T Technology (General)
• Online Access: http://eprints.uthm.edu.my/10960/1/24p%20NOR%20ASMALINDA%20KAMARUDDIN.pdf; http://eprints.uthm.edu.my/10960/2/NOR%20ASMALINDA%20KAMARUDDIN%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/10960/3/NOR%20ASMALINDA%20KAMARUDDIN%20WATERMARK.pdf; http://eprints.uthm.edu.my/10960/

Currently, agricultural waste derivatives have been incorporated with synthetic particles into a new generation of hybrid aluminium matrix composites (AMC) due to their excellent properties such as low density, accessibility, ability to reduce environmental pollution, and low production cost. This research investigates the effects of particle size of alumina (Al2O3) and composition of rice husk silica (RHA) as reinforcements of hybrid recycled aluminium chip composites using the cold compaction process. The AA7075 chip was reinforced with rice husk and alumina powder at range 0.5 -10.5 wt.%. Rice husk and alumina particles were 63 μm and 1.0 μm to 35.0 μm, respectively. Physically, AMC density increased with Al2O3 particle size. The highest density, porosity, and water absorption were found at 35.0 μm, with 2.5654 g cm-3, 7.49%, and 3.18%, respectively; the lowest were found at 1.0 μm, with 2.3485 g cm-3, 0.62%, and 0.24%. The density decreased by 3.0 wt.%, rose to 8.0 wt.%, then dropped. Density inversely affects porosity and water absorption. Mechanically, the maximum hardness and compression strength are 5.0 μm and 1.0 μm of Al2O3, respectively. Hardness and compression strength decreased with RHA content. At 0.5 wt.% RHA, hardness and compression strength were 111.99 HV and 174.62 MPa. At 10.5% RHA, hardness and compression strength are 53.70 HV and 65.58 MPa. As particle size increases, the distance between reinforcements increases, resulting in coarser grains. More RHA reduces pore formation and makes pores smaller and rounder. When RHA and Al2O3 are added, hybrid aluminium composites work better in aerospace, cars, marines, and electronics