Dr. Sunil Mohan, Professor, Indian Institute of Technology (BHU) Varanasi (IIT-BHU), India

Sunil Mohan is Professor of Metallurgy in IIT (BHU), Varanasi, India. He completed his B. E., M.E. and Ph.D. from erstwhile University of Roorkee/IITR. He is teaching at IIT (BHU) for over 25 years His area of teaching is Composite Materials, Surface Engineering, Transport Phenomena, Modelling and Simulation. He is working in the area of alloy development, synthesis of composites by different routes and tribology of materials for more than 26 years. He has published more than eighty research papers in National and International Refereed Journals. He has guided several M. Techs. and PhDs. He is life member of Tribological Society and Electron Microscopy Society of India.

Speech Title: Enhancing Strength of Materials with Reinforcement

Aims: Studying strengthening behavior of insitu composites.

Methods: AA5052 aluminum alloy and two inorganic salts K₂ZrF₆ and KBF₄ were used as raw materials to prepare the composites. Inorganic salts were dehydrated in an electric oven at 250⁰C for 3 h to remove the moisture. Mixture of K₂ZrF₆ and KBF₄ in a definite ratio was introduced into molten AA5052 alloy at 8600C. After stirring with a graphite stirrer at 860⁰C for about 30 mins and degassing with hexa-chloroethane (C₂Cl₆), composite melt was cast into a preheated metal mould. This way composite with ZrB₂ particles and hybrid composite with (Al₃Zr+ZrB₂) particles were formed by insitu reaction of salts and molten metal. Composites produced by insitu reaction of aluminum alloy and inorganic salts exhibited superior strength as compared to AA5052 matrix alloy.

Results: Strengthening in such composites may take place by four different mechanism
such as Orowan strengthening which occurs due to interaction of dislocations with insitu formed particles, that restricts crack propagation during tensile. Particles act as hinderance to dislocation movement creating a strain field around particles. Dislocation strengthening takes place due to the presence of dislocations in the matrix. Insitu formation of reinforcement particles restricts the growth of aluminium rich grains and lead to grain refinement strengthening and finally presence of different alloying elements solid solution strengthening occurs. These mechanisms contribute differently in various systems. Both composites were studied for contribution of different mechanisms.

Conclusions: It was observed that Orowan and solid solution strengthening are most predominant mechanisms for improved strength while grain refinement has least contribution in the improvement of composites.