Browsing by Author "Prasad, Rajesh"

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Characterization of Deformation and Wear Mechanisms During Indentation Scratching on Pure Zinc
(2020-01-01)
Gokhale, Aditya
;
Jain, Jayant
;
Prasad, Rajesh
;
Huang, E-Wen
;
Lee, Soo Yeol
Scratch testing using nanoindentation helps to characterize material's wear resistance and the accompanying material removal, and deformation mechanism. The effect of load and repeated scratching on pure zinc was investigated in this study. Surface examination post scratching revealed the formation of long chips at lower loads, which can be attributed to ductile-like behavior. Ploughing dominated at higher loads, while micro-cutting was active at lower loads. The material removal factor (f(ab)) is an indicator of the prevailing wear mechanism. A good correlation appeared between the observed wear mechanism and the calculated fab, wherein interplay of ploughing and micro-cutting was observed. The decrease in wear rate as the number of passes increased and the decreasing value of fab are indicative of the strain hardening behavior during repeated scratching. The presence of intergranular fracture slip and twinning on the deformed surface is indicative of the material's response to induced stress.
Quantitative evaluation of grain boundary sliding and its dependence on orientation and temperature in pure Zn
(2019-07-01)
Gokhale, Aditya
;
Sarvesha, R.
;
Huang, E-Wen
;
Lee, Soo Yeol
;
Prasad, Rajesh
In the present work, grain boundary sliding (GBS) has been studied for the grains exhibiting different orientations (for indentation parallel and perpendicular to < c > axis) at different temperatures (RT to 200 degrees C) using nanoindentation in pure Zn. Electron back scattered diffraction was utilized to determine the orientation of the indented grains and identify the deformation mechanism, whereas atomic force microscopy was utilized to systematically quantify the GBS. Results indicated that indentation perpendicular to < c > axis exhibits slip induced GBS, whereas the indentation parallel to < c > axis results in pure GBS. The amount of GBS was also found to be strongly dependent upon the orientation of the neighboring grain. Further, the contribution from GBS towards total stain was found to increase with an increase in temperature. (C) 2019 Elsevier B.V. All rights reserved.