Department of Biomedical Engineering, City University of Hong Kong, Hong Kong SAR, P.R. China

Biography: Prof. Rao received bachelor degree in engineering from Karnataka Regional Engineering College (National Institute of Technology), Surathkal, master degree from Indian Institute of Technology, Kanpur, and PhD from Indian Institute of Technology, Madras, Chennai, India. He also holds MBA degree in Technology Management from LaTrobe University, Australia. After working as research engineer for 3 years, he pursued post-doctoral fellowships at University of New Brunswick and University of British Columbia, Canada, before commencing his academic career at City University of Hong Kong in 1990. Here, he served in various capacities for the past 29 years in the departments of Manufacturing Engineering and Engineering Management, Mechanical and Biomedical Engineering, and currently as Visiting Professor in Biomedical Engineering. His current research is mainly on the development and processing of new light-weight magnesium-based alloys for applications in electronic, automobile, aerospace, and biomedical industries. He completed over 30 funded research projects and published over 150 papers in international journals.

Speech Title: Strength, Hot Workability, and Forming of Mg-4Al-2Ba-1Ca Alloy

Abstract: While the addition of aluminum enhances strength of magnesium, high temperature creep resistance in cast alloys can be enhanced by inclusion of barium and calcium. The mechanical properties will be much better in wrought condition by the elimination of dendritic structure, chemical segregation, and microporosity associated with the cast microstructure. In this study, quaternary alloy Mg-4Al-2Ba-1Ca was investigated in detail with regard to its strength in the application range of temperature, workability and microstructural evolution at high temperatures and deformation speeds, and forming of cast alloy into a complex component using an industry-standard metal forming process like forging. It is found that the compressive strength of the alloy gradually decreased from 243 MPa at room temperature to 138 MPa at 200°C that matches with the performance of a popular alloy MRI230D. The hot working behavior of the alloy has been analyzed using kinetic analysis and processing maps, and windows for safe forming of this alloy have been established. The processing map exhibited two workability domains, and their true relevance has been validated by attempting to forge a rib-web (cup) shape component in the temperature range 300–500°C and forging speeds of 0.01, 0.1, 1, and 10 mm s-1. Finite-element simulations were also conducted for the corresponding conditions so as to obtain the developing strain and strain rate distributions within the component during forging. The targeted cup shape components have been successfully forged under the optimal/safe domain conditions, and the microstructures in these components revealed dynamically recrystallized fine grains of uniform size. The components forged under the conditions of instability/damage regime have fractured, and the microstructures exhibited flow localization bands and cracks.

Keywords: Magnesium alloy, Compressive strength, Hot workability, Forming, Computer simulation