Thermal Properties of As-Cast Bottom Ash Reinforced Aluminum Metal Matrix Composite

Abstract

The purpose of this research is to study characteristics of composite Al 6061  + coal ash, namely: thermal conductivity, linear thermal expansion, and melting point, density, porosity and hardness. Before testing, we carried out T6 treatment of material, where the material solution underwent to sintering at 538 °C during 16 h, then quenching, and artificial ageing. We studied the following cases: for temperatures 200, 225, 250 °C and holding times 8, 12, 16 h. The thermal conductivity tests were performed by using DSC (Differential Scanning Calorimetry) and TDA (Thermal Dilatometry Analysis) for linear thermal expansion, for melting point were used trial and error tests, Archimedes principle was used for density test, and hardness testing by Brinell hardness test. In this study, a minimum value of thermal conductivity factor (5.703 W/m K) was obtained at a temperature 200 °C with holding time 8 h, and a maximum value (8.314 W/m K) was obtained at a temperature 225 °C with holding time 12 h. Minimum value of linear thermal expansion (4.6238 × 10⁻⁴/°C) was obtained at a temperature 225 °C with holding time 16 h and maximum value (7.7312 × 10⁻⁴/°C) was obtained at a temperature 200 °C with holding time 8 h. The result of test melting point is 700–1000 °C, the optimum value of test density is 2.4044 g/cm³ at 250 °C with holding time 8 h. The optimum value of porosity is 2.8876% at 250 °C with 8 h holding time. The higher aging temperature leads to longer holding time for the material during aging, the diffusion which occurs will be greater so the shrinkage will be even bigger causing a reduction in the volume of large pores. The maximum hardness was attained for the sample at 250 °C and holding time 12 h; the minimum hardness was found for the sample at 200 °C, and holding time 8 h.