Seminar on Using bulk metallic glass and its composites as structural materials: a metallurgical perspective

Dr Lakshmi Narayan R

Assistant Professor 

Department of Materials Science and Engineering, Indian Institute of Technology Delhi

Bulk metallic glasses (BMGs) are multicomponent metallic alloys that possess ten times higher strengths and elastic limits compared to conventional engineering alloys. They also possess near net shape formability at the glass transition temperature, allowing them to be molded into any desired shape. Despite these advantages, they are not yet popular as structural materials because they undergo shear localization during plastic deformation, which leads to poor toughness and negligible ductility. Therefore, one of the grand challenges in materials engineering is to improve the toughness of BMGs without compromising its strength. In this talk, a clear distinction between the concept of toughness and fracture toughness will be made. Factors controlling the fracture toughness of BMGs and the importance of fracture toughness on engineering design will be emphasized. Then, the solution to the problem of ductility will be addressed by employing the composite approach, wherein a crystalline dendritic reinforcement is precipitated inside the metallic glass. This will be followed by performing a classical microstructure-mechanical property correlation study on BMG composites (BMGCs). A detailed investigation on the effect of different microstructural length scales and the metastability of the reinforcements on different mechanical properties and fracture toughness of the BMGC will be described. Thereafter, the conditions leading to embrittlement of these BMGCs will also be considered. Cryogenic cycling to rejuvenate the embrittled BMGC will be explained, and a critical assessment of the procedure will be discussed. Finally, the current state of research on BMGs will be brought into perspective and future challenges will be discussed.

Dr R. Lakshmi Narayan is an Assistant Professor in the Department of Materials Science and Engineering at IIT Delhi in India. He received his PhD from IISc Bangalore and joined the Carnegie Mellon University as a Postdoctoral Fellow. During this time, he was also a visiting scientist in Xi’an Jiaotong University, Xi’an, China. He received the prestigious Gopalakrishnan-NTU Presidential Postdoctoral Fellowship in Nanyang Technological University, Singapore and worked with the Singapore Centre for 3D printing (SC3DP). Dr Lakshmi Narayan's research is focused on understanding the multiscale processing-structure-property correlations in advanced materials such as additively manufactured or 3D printed metals and alloys, nanoglasses, metallic glasses and their composites, Mg alloys and high temperature Ni based superalloys. He was awarded the K.P. Abraham Gold Medal for his PhD thesis and more recently conferred with the Indian National Science Academy’s prestigious INSA medal for young scientists, which is the highest honor for scientists and engineers younger than 35 in India.