Time-Dependent Evolution of Al-Al₄C₃ Composite Microstructure and Hardness during the Sintering Process.

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Aluminum-aluminum carbide (Al-Al4C3) composites are engineered materials with potential applications in various industries.
• Understanding their microstructural evolution and mechanical properties is crucial for optimizing performance.

Purpose of the Study:

• To investigate the microstructural changes and mechanical property enhancements in Al-Al4C3 composites after heat treatment and sintering.
• To elucidate the role of dislocations and nanorod formation in the composite's hardening mechanism.

Main Methods:

• Mechanical milling followed by heat treatment and sintering at 550 °C for varying durations (2, 4, 6 h).
• Microstructural analysis using High-Resolution Transmission Electron Microscopy (HRTEM) and Geometric Phase Analysis (GPA).
• X-ray diffraction (XRD) pattern analysis via the Convolutional Multiple Whole Profile (CMWP) method.

Main Results:

• A 75% increase in hardness was observed after 2 h of sintering, attributed to the nucleation and growth of Al4C3 nanorods.
• HRTEM and GPA revealed strain fields associated with partial screw dislocations and dislocation dipoles at the Al-Al4C3 interface.
• XRD analysis confirmed the predominance of screw-type dislocations and their correlation with dislocation dipoles.

Conclusions:

• Dislocation density and crystallite size are primary contributors to hardening before sintering.
• Sintering significantly enhances hardness through nanorod formation and specific dislocation behaviors.
• Optimizing reinforcement content and sintering time may reduce brittleness in Al/Al4C3 composites.