PSI - Issue 27

Hammar Ilham Akbar et al. / Procedia Structural Integrity 27 (2020) 30–37 Akbar et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The mechanical properties of Al-Fly ash/Bottom ash composites can be improved with heat treatment. Identification of thermal properties in as-cast AMC with bottom ash reinforcement conducted by T6 heat treatment (Seputro et al., 2017) produces the highest thermal conductivity at 225ºC for 12 hours at 7.03 W/mK. The longer the time and the higher the temperature, the heat treatment decreases linear thermal expansion from 2.46/K at 200ºC to 1.77/K at 250ºC. The highest hardness is obtained at 250ºC for 12 hours and decreases with increasing heat treatment time. Effect of T6 heat treatment on Al-Bottom ash composites on reaction products on the matrix interface and reinforcement produces a new Al 2 MgSiO 4 phase (Abdulrahim and Seputro, 2016). 2.2. Red mud Red mud is the waste produced in alumina production by the aluminum industry. The higher aluminum production in the last few years will make more red mud waste produced. Every 2.5 tons of alumina production produces 1.5 tons of red mud waste. Around 120 million tons of red mud is provided by the aluminum industry each year (Bodunrin et al., 2015; Chinta et al., 2018; Feng and Yang, 2018; Gangadharappa et al., 2018). Red mud contains abundant aluminum, iron, and other rare elements such as scandium, titanium, and vanadium (Feng and Yang, 2018). The ceramics compound has contained in red mud has shown in Table 2 . Table 2. Chemical composition of Red mud (Harshavardhan et al., 2018) . Elements Al 2 O 3 Fe 2 O 3 SiO 2 TiO 2 Na 2 O CaO LOI Content % 18.34 45.93 7.23 9.56 3.42 1.0015 8.0014 The use of red mud as reinforcement in aluminum matrix composites results in an increase in hardness from 60.2 HVN to 74.5 HVN when the red mud fraction increases from 2% wt to 6% wt. When the red mud particle size is varied from 100-200 µm, the hardness will decrease from 74.5 HVN to 63.5 HVN. When the particles are nano sized, the hardness will increase by 11.2% compared to the highest hardness of 100 µm (Chinta et al., 2018). Evaluation of fracture toughness in Al-Red mud composites compared with pure aluminum shows that the maximum load increased by 35% at the addition of 12% wt red mud. Then decreased at the addition of 16% wt red mud, where the stress intensity factor K 1 C increased 6% at 12% wt red mud and down when red clay is increased to 16% wt (Harshavardhan et al., 2018). 3. Agro-waste reinforcement Agricultural wastes have been known to contain elements that can be used as reinforcement in metal matrix composites. Apart from that, agricultural waste also has abundant and cheap material availability. The addition of agricultural waste is not only beneficial in terms of the industry but also benefits the environmental side by reducing pollution (Joseph and Babaremu, 2019). Various types of agricultural waste such as rice husk ash (RHA), bagasse, groundnut shell, and coconut shell have been used as reinforcement for metal matrix composites. 3.1. Rice husk ash RHA is a more economical reinforcement compared to conventional ceramic reinforcement used in metal matrix composites (Dinaharan et al., 2017). RHA is an agricultural waste that is abundant throughout the world. RHA comes from the rice milling process that produces rice, bran, and husk, which is used rice milling as fuel. The burning residue is called RHA (Gladston et al., 2017). The chemical composition of RHA is shown in Table 3. Table 3. Chemical composition of RHA (Gladston et al., 2017). Element SiO 2 Al 2 O 3 C CaO MgO K 2 O Fe 2 O 3 LOI wt.% 90.23 3.54 1.23 1.58 0.53 0.39 0.21 2.29 Al6061/18% wt RHA composites using the Friction Stir Processing (FSP) manufacturing method produce composites without segregation or agglomeration. This condition is caused by the tool rotation in the manufacturing process (Dinaharan et al., 2017). The fracture surface shows a ductile fracture marked by a dimple. The ductile