Faculty Publications
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Item Determination of spread activation energy and assessment of wetting behavior of solders on metallic substrates(American Society of Mechanical Engineers (ASME), 2010) Prabhu, K.N.; Kumar, G.The effects of substrate material, substrate surface roughness, and operating temperature on the wetting behavior of Sn-37Pb, Sn-3.5Ag, and Sn-9Zn eutectic solders on metallic substrates were investigated. Solder spreading kinetics was successfully represented by the exponential power law (EPL): ?=exp (-K ?n). The EPL parameter K has the significance of accelerating the kinetics of relaxation while the parameter n represents the resistance to spreading process (spread resistance parameter). EPL parameters exhibited a decreasing trend with an increase in surface roughness. Estimated activation energies for solder spreading were found to be in between those reported for inert and highly reactive spreading systems. © 2010 American Society of Mechanical Engineers.Item Influence of Ball Burnishing Process on Equal Channel Angular Pressed Mg-Zn-Si Alloy on the Evolution of Microstructure and Corrosion Properties(Springer Science and Business Media B.V., 2021) Ramesh, S.; Anne, G.; Kumar, G.; Jagadeesh, C.; Shivananda Nayaka, H.In the present study, Mg-4Zn-1Si alloy was subjected to equal channel angular pressing (ECAP) up to 4 passes at 300 °C, followed by ball burnishing using 0.3 mm depth of press, 300 mm/min feed and 1 pass successfully. The effect of ECAP and ECAP + ball burnishing process on microstructure, mechanical properties (tensile and hardness) and corrosion behavior was systematically investigated. After 4 pass ECAP, initial coarse grains (210 ?m) were refined and average grain size is 6 ?m and after ball burnishing, the grain size is found to be 3.3 ?m. Microstructure evolution is discussed using optical images, scanning electron microscope images and transmission electron microscope images. For ECAP samples, maximum strength and hardness was recorded at 3 pass. Both strength and hardness decreased for 4 pass ECAP processed samples, even though grain size decreased, this is because of texture modification in the material. ECAP 4 pass + ball burnished samples exhibited 48.5% enhancement of microhardness as compared to 4 pass ECAP samples. Corrosion resistance of the samples decreased with increase in the number of ECAP passes, this is due to strain-induced grain refinement with more crystalline defects in samples. Combined process of ECAP and ball burnishing effectively reduces the Icorr and this consequently reduces corrosion rate of the Mg–4Zn-1Si alloy. © 2020, Springer Nature B.V.Item Effect of Equal Channel Angular Pressing on Properties Evaluation of Biodegradable Mg-Zn-Mn Alloy(Springer Science and Business Media Deutschland GmbH, 2021) Ramesh, S.; Kumar, G.; Jagadeesh, C.; Anne, G.; Shivananda Nayaka, H.Equal channel angular pressing (ECAP) was used to process Mg-4Zn-1Mn alloy at 300 °C using route Bc up to 4 pass with a cumulative strain of 3.2. Optical microscope (OM), microstructures results shows homogenized sample grain size was 260 µm, after 4 pass ECAP grain size was decreased to 6 µm. Electron back-scattered diffraction (EBSD) shows the misorientation angle converted from low-angle grain boundaries (LAGB) to high-angle grain boundaries (HAGB). Dislocation density and fine grains were observed from transmission electron microscope (TEM) images. Strength has been increased from 156 to 218 MPa and hardness increased to 68 Hv after 4 pass of ECAP. Fractography analysis revealed that dimple size decreases as ECAP passes increased. XRD analysis shows the peak broadening and intensity variation, because of grain refinement. The corrosion behavior of the homogenized and ECAP-processed samples were investigated by electrochemical tests using simulated body fluids (SBF) at 37 ± 1 °C. The lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn alloy attributed to the strain-induced crystalline defects, subgrain boundaries and high-density dislocations. Enhanced strength and ductility combined with lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn has greater potentials for biomedical implants. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.