Grain Refinement of Aluminum using ECAP process.pptx

CLass notes

1. Grain Refining of Aluminum Class 2: New metals in manufacturing

2. Grain refining of aluminum is a process used to improve its mechanical properties, castability , and surface finish by reducing the grain size during solidification. Finer grains enhance strength, ductility, machinability, and corrosion resistance. Grain Refining of Aluminum

3. Addition of Grain Refiners (Nucleation Control) Adding grain-refining agents introduces nucleation sites, which promote finer grain structures. Common grain refiners include: Al-Ti-B ( Aluminium -Titanium-Boron) Master Alloys Most widely used grain refiner. Titanium (Ti) forms TiAl ₃ particles, while Boron (B) forms TiB ₂ particles, both acting as nucleation sites. Al-Ti-C ( Aluminium -Titanium-Carbon) Master Alloys Methods of Grain Refining in Aluminium

4. Carbon (C) in the form of TiC improves grain refinement performance. Used in high-performance casting applications. Al- Zr ( Aluminium -Zirconium) Alloys Zirconium-based refiners provide long-lasting grain refinement at high temperatures. Used in aerospace and high-temperature aluminium alloys. 2. Rapid Solidification (Cooling Rate Control) Faster cooling during casting leads to finer grains because there is less time for grain growth. Methods of Grain Refining in Aluminium

5. Techniques like die casting, electromagnetic stirring, and spray deposition enhance grain refinement. 3. Ultrasonic Treatment High-frequency ultrasonic waves break up dendritic structures in molten aluminium . This process promotes nucleation and reduces grain size. Used in advanced manufacturing for aerospace and automotive applications. 4. Mechanical Stirring & Electromagnetic Stirring Stirring the molten aluminium (mechanically or using electromagnetic fields) disrupts grain growth and promotes fine grain structure. Methods of Grain Refining in Aluminium

6. Often combined with grain refiner additions for maximum effect. 5. Strain-Induced Grain Refinement (Thermo-Mechanical Processing) Rolling, extrusion, or forging breaks down coarse grains and refines the microstructure. Severe Plastic Deformation (SPD) techniques like Equal Channel Angular Pressing (ECAP) produce ultra-fine grains. Methods of Grain Refining in Aluminium

7. ✔ Higher Strength & Toughness – Finer grains improve mechanical properties. ✔ Better Machinability & Weldability – Makes aluminium easier to process. ✔ Reduced Porosity & Cracking – Improves casting quality. ✔ Improved Corrosion Resistance – Smaller grains reduce localized corrosion. ✔ Better Surface Finish – Crucial for automotive and aerospace applications. Advantages of Grain Refinement in Aluminium

8. Equal Channel Angular Pressing (ECAP) produce Equal Channel Angular Pressing (ECAP) – A Grain Refinement Technique Equal Channel Angular Pressing (ECAP) is a severe plastic deformation (SPD) technique used to refine the grain structure of metals, including aluminium and magnesium. It enhances mechanical properties such as strength, hardness, and ductility by producing ultra-fine grains (UFG) without changing the material’s shape.

9. Equal Channel Angular Pressing (ECAP) produce How ECAP Works Metal Billet Preparation A metallic billet (block or rod) is prepared and placed into a die with an L-shaped or angular channel. 1. Severe Plastic Deformation The billet is forced through the angular channel under high pressure. The sharp bend (typically 90° to 120°) causes intense shear deformation, breaking down coarse grains.

10. Equal Channel Angular Pressing (ECAP) produce This process is repeated multiple times to refine the grain size further. Microstructural Changes The process introduces dislocations and refines grains to the nano or sub-micron level. After several passes, an ultra-fine-grained (UFG) structure is achieved.

11. Benefits of ECAP ✔ Significant Grain Refinement – Produces ultra-fine grains (as small as 100–500 nm). ✔ Increased Strength & Hardness – Due to the Hall- Petch effect (finer grains = higher strength). ✔ Enhanced Ductility & Toughness – Unlike regular cold working, ECAP retains good ductility. ✔ Improved Fatigue & Wear Resistance – Useful in aerospace, automotive, and biomedical industries. ✔ Retained Original Shape – The billet keeps its initial shape, making it reusable in further processing.

12. Applications of ECAP Aerospace & Automotive Components – High-strength aluminium and magnesium alloys. Biomedical Implants – High-purity titanium and magnesium with better biocompatibility. Electronics & Conductive Materials – Ultra-fine-grained copper and aluminium for high-performance applications.