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<p>The development of Al-Si based composites are widely recognized as an advance engineering material for potential light weight applications in automotive and aerospace industries, enhancing fuel efficiency and sustainability. The present study aims to develop and investigate the microstructure, solidification kinetics and strengthening mechanism for Al-12wt%Si-(TiB<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub>) hybrid composite with 7.5%, 10.5%, 12.5% and 15% weight percentage of reinforcements. Processing parameters were optimized by calculating the molar Gibbs free energy and reinforcements were synthesized via salt-metal reactions in the stir casting method. The composite exhibited bimodal TiB<sub>2</sub> particles at nano and microscale and Al<sub>2</sub>O<sub>3</sub> particles at nanoscale clustered with TiB<sub>2</sub>. Addition of the reinforcements to the Al-Si melt alters the microstructure from globular eutectic to divorced eutectic with the diffusion and interface-controlled growth as governed by the Avrami kinetics. At a constant cooling rate of 127.35&#xa0;°C/s, the grain size refinement was governed by the increasing percentage of TiB<sub>2</sub> particles. Increase in the reinforcement percentage from 7.5% to 15% refined the TiB<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> particle size from 0.75&#xa0;µm to 0.54&#xa0;µm and 0.42&#xa0;µm to 0.31&#xa0;µm respectively. This enables significant contribution of the Orowan strengthening mechanism (11.32%-17.70%) leading to improvement in the tensile strength from 214.57&#xa0;MPa to 309.83&#xa0;MPa. Coefficient of thermal expansion mismatch was observed to be the key strengthening mechanism with a contribution of 31.44%-42.16%. Fractographic analysis revealed a complex fracture surface with a mixed ductile–brittle failure mode, featuring dimples and large voids indicative of ductile behaviour, alongside cracked silicon particles, highlighting brittle fracture.</p>

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Investigation of Solidification Behavior and Strengthening in Al-Si Based Hybrid Composites Fabricated Through In-Situ Stir Casting Route

  • 期刊论文

  • 发表日期：

    2025年3月10日

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  • Sudhir Ranjan,
  • Pradeep Kumar Jha

摘要

The development of Al-Si based composites are widely recognized as an advance engineering material for potential light weight applications in automotive and aerospace industries, enhancing fuel efficiency and sustainability. The present study aims to develop and investigate the microstructure, solidification kinetics and strengthening mechanism for Al-12wt%Si-(TiB2 + Al2O3) hybrid composite with 7.5%, 10.5%, 12.5% and 15% weight percentage of reinforcements. Processing parameters were optimized by calculating the molar Gibbs free energy and reinforcements were synthesized via salt-metal reactions in the stir casting method. The composite exhibited bimodal TiB2 particles at nano and microscale and Al2O3 particles at nanoscale clustered with TiB2. Addition of the reinforcements to the Al-Si melt alters the microstructure from globular eutectic to divorced eutectic with the diffusion and interface-controlled growth as governed by the Avrami kinetics. At a constant cooling rate of 127.35 °C/s, the grain size refinement was governed by the increasing percentage of TiB2 particles. Increase in the reinforcement percentage from 7.5% to 15% refined the TiB2 and Al2O3 particle size from 0.75 µm to 0.54 µm and 0.42 µm to 0.31 µm respectively. This enables significant contribution of the Orowan strengthening mechanism (11.32%-17.70%) leading to improvement in the tensile strength from 214.57 MPa to 309.83 MPa. Coefficient of thermal expansion mismatch was observed to be the key strengthening mechanism with a contribution of 31.44%-42.16%. Fractographic analysis revealed a complex fracture surface with a mixed ductile–brittle failure mode, featuring dimples and large voids indicative of ductile behaviour, alongside cracked silicon particles, highlighting brittle fracture.