Ph.D. (2011 - 2016), Indian Institute of Technology Madras. Chennai, India.
Area of Research: Metallurgical & Materials Engineering - Alloy development (Alloy design - Microstructure - Mechanical property correlation)
Title of Thesis: Effect of Sc on the microstructure, mechanical and wear behavior of A356 alloy and A356 -5TiB2 in situ composite.
Research Highlights:
Al–Si alloys and Al-matrix composites (AMCs) have received much attention for automobile, aerospace and structural applications due to their high specific strength, specific stiffness, higher hardness, wear resistance and good elevated temperature resistance. A356 alloys are used to manufacture sand cast and gravity cast automotive components. Usually, these alloys are used after the addition of grain refiners and eutectic Si modifiers to improve the strength. Only recently, researchers have started using Sc as eutectic Si modifier and grain refiner in Al-Si alloys. My Ph.D research was on the effect of 0.2 and 0.4 wt.% Sc addition on the microstructural modification and its effect on mechanical and wear properties in A356 alloy and A356-5 wt.% TiB2 in-situ composites.
Microstructural Modification: Addition of 0.4 wt.% Sc in A356 alloy resulted in a 50% reduction in the secondary dendritic arm spacing (SDAS). Al3Sc particles act as a heterogeneous nucleation sites for α-Al during solidification of A365-Sc alloy resulting in grain refinement. SC addition changed the morphology of eutectic Si from plate like to fibrous and globular.
Sc addition changed the morphology of eutectic Si from plate like to fibrous and globular. In case of hypoeutectic Al-Si alloys, Si growth is by twin plane re-entrant edge (TPRE) growth mechanism and eutectic Si is in plate like morphology. Twins are the significance of TPRE growth and were found over the growth direction of Si in unmodified eutectic Si. Twins were not observed in eutectic Si and for Sc added A356 alloy. This clearly indicate that the Si growth is not by TPRE mechanism. Hence, poisoning of TPRE growth or restricted TPRE growth mechanism was proposed, which is responsible for the modification of eutectic Si in Sc added A356 alloy
Advanced microstructure Characterization: Advanced material characterization tools like Transmission electron microscopy (TEM) and XRD (X ray diffraction) were used to analyse the phase modification. TEM diffraction pattern, Energy dispersive spectroscopy (EDS) and XRD analysis revealed the presence of β-Al5FeSi and π-Al8Mg3Si6Fe1 phases in A356 alloy. Addition of Sc to A356 alloy resulted in an additional V-AlSi2Sc2phase formation and changed β and π phases to Sc containing β-Al5Fe(Si.Sc), π-Al8Mg3(Si,Sc)6Fe1 phases. The β-Al5Fe(Si,Sc) phase is finer sized and irregular morphology compared with needle like morphology β-Al5FeSi phase.
Mechanical and Wear Behaviour: Addition of 0.4 wt.% Sc to A356 alloy improved its Vickers hardness, Ultimate tensile strength (UTS), Yield strength (YS) and Ductility by 20%, 25%, 20% and 30% respectively. Whereas, A356-5TiB2-0.4Sc in-situ composite showed a 30%, 24%, 33% and 7% improvement in Vickers hardness, UTS, Yield strength and Ductility respectively, compared with A356 alloy. Artificial aging treatment (T6) resulted in significant improvement in the tensile properties for both A356 and Sc added A356 alloys. Pin-on-disk wear test results indicated that Sc addition improves the wear resistance of A356 alloy and A356-5 wt.% TiB2 composite at ambient, 150oC and 250oC temperature test conditions.
Position of Responsibilities Undertaken in IIT Madras
Chair, Material Advantage Student Chapter, IIT Madras (2011-2013).
Active representation in organizing technical events at UG, PG and Ph.D levels.
Technical committee member for ISRS 2012 and ISRS 2014 international conferences.
Internship / Student Exchange Program
Visiting Scholar (4 months, March, 2012 to July, 2012)., Ryerson University, Canada.
Development of Magnesium based alloys and composites for Automotive application.
Canadian Commonwealth Scholarship from Canadian Bureau for International Education (CBIE) and Foreign Affairs and International Trade Canada (DFAIT) to undergo research work in Ryerson University, Toronto, Canada for four months (15 March – 15 July, 2012).
M.E. Industrial Metallurgy (2008-2010), PSG College of Technology, Coimbatore, (Anna University).
Title of Thesis: Processing and characterization of Silicon Carbide (SiC) reinforced functionally graded Aluminium matrix composites using centrifugal casting.
Research Highlights: Functionally graded A356-15 wt.% SiC composite disks were fabricated by centrifugal casting for clutch plate application in defense battle tank. The outer periphery of the clutch plate requires high strength and wear resistance since these are continuously engaging/disengaging while operation. The processing parameters, pouring temperature and rotation speed were optimized to get a graded microstructure without porosity and shrinkage. The tensile and wear properties showed significant improvement in the outer periphery relative to inner periphery of the disk. This work was carried out in National Institute for Interdisciplinary Science and Technology (CSIR), Trivandrum, Kerala, India as a part of a project with Combat Vehicles Research and Development Establishment.
Awards/ Accomplishments: Awarded Best Project and Outstanding Student award of 2008-2010 batch of M.E. Industrial Metallurgy.