Influence of Solid Fraction Casting on Microstructure of Aluminum Alloy 6061

Abstract

Semi-solid processing of AA6061 alloy near liquidus temperature with the addition of micro- and nanoparticles of same alloy may be highly attractive for small intricate shapes due to excellent mechanical properties. The present work utilizes semi-solid behavior of AA6061 alloy, which reduces macro- and nanosegregation of particles, porosity, and forming forces during the shaping process. The experiment utilizes the semi-solid slurry of different solid fractions mixed with a melt at pouring temperature range of 400 − 640°C. The potential of solid fraction to produce semi-solid slurry has been investigated with the help of microstructure analysis, which is a crucial need for aluminum industries. The result shows that during the stirring, every dendrite modified itself to fine solid grains and dispersion of these grains takes place inside the molten metal. Alloy cooled directly from semi-solid state results in higher relative density with respect to conventional casting. With increase of solid fraction to 25%, the un-melted solid structure inside the pores and cavities in the direction of elongated grains results in the subsequent enhancement in the impact strength, hardness, and compressive strength as 19 kJ/m², 93 BHN, and 550 MPa, respectively, without any alteration in the basic metal matrix composite.

Keywords:

• High solid fraction low-temperature cast
• Low solid fraction high-temperature cast
• Semi-solid casting
• Solid effect

ACKNOWLEDGMENTS

The authors thank Dr. Prabhat Kumar Dwivedi, Indian Institute of Technology, Kanpur, India, for his assistance extended during this work. Authors highly appreciate the contribution of Mr. Balwinder Singh, G.S. Auto International Limited, Ludhiana, India, who has taken great pleasure in conducting experiments at various stages. The authors also acknowledge the efforts of all the staff members of Mechanical Engineering Workshop and Machine Element Design Lab of Motilal Nehru National Institute of Technology, Allahabad, India.