Browsing by Author "Kumar, G.V.P."

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Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy
(2018) Manjunath, G.K.; Kumar, G.V.P.; Bhat, K.U.
The current investigation is focused on evaluating the mechanical properties and the microstructure of cast Al-10Zn-2Mg alloy processed through equal channel angular pressing (ECAP). The ECAP processing was attempted at minimum possible processing temperature. Microstructural characterization was carried out in optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Hardness measurement and tensile tests were employed to estimate the mechanical properties. Experimental results showed that, ECAP processing leads to noticeable grain refinement in the alloy. Reasonable amount of dislocations were observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was detected in the XRD analysis. ECAP leads to considerable enhancement in the mechanical properties of the material. After ECAP processing, microhardness of the material is increased from 144 Hv to 216 Hv. Also, after ECAP processing the UTS of the material is increased from 140 MPa to 302 MPa. The increase in the mechanical properties of the alloy after ECAP processing is due to the dislocation strengthening and grain refinement strengthening. Finally, fracture surface morphology of the tensile test samples also studied. � 2018 Author(s).
Effect of multi directional forging on impression creep behavior of Zn-24Al-2Cu alloy
(2018) Sharath, P.C.; Rajendra, Udupa, K.; Kumar, G.V.P.
Multi directional forging (MDF) of Zn-24Al-2Cu alloy were carried at 100�C and 200�C with total equivalent strain of 0.6 and 1.2 respectively. The average grain size was reduced from 30 to 1 ?m after MDF processing. Impression creep behavior of MDF processed samples was studied at 2 kg and 2.5 kg load with temperatures 30, 50, 100 and 150�C. Microstructural characterizations were carried out using optical microscope, transmission electron microscope and X-Ray diffractometer. Steady state creep rate values were recorded in the range of 1.2x10-5 to 5.2x10-7. The four phase transformation occurred in the structure after MDF process and during the impression creep test. Initial stress exponent (n) values are in the range of 2.5 to greater than 5. High values of 'n' showed due to the existence of threshold stress. The true activation energy values calculated are in the range of 22-129 kJ/mol. Changes in creep properties of MDF processed samples seem to be more sensitive to change in temperature compared to microstructural differences. Lattice diffusion controlled by dislocation climb is the dominant creep mechanism. � 2018 Elsevier Ltd. All rights reserved.
Effect of Multi-Axial Room-Temperature Forging on Scratch Hardness and Wear Properties of Hypoeutectic Al-7.3Si and Eutectic Al-12.1Si Alloys
(Springer, 2024) Kumara, B.; Kumar, G.V.P.
In this work, effect of multi-axial room temperature forging process on scratch and wear characteristics of Al-7.3 and Al-12.1Si alloys with varying cumulative strains was investigated. Al-7.3 and Al-12.1Si alloy ingots were remelted in a furnace and then poured into a preheated die to produce a cast sample of the desired shape and dimension for the MAF process. These samples were subjected to solution heat treatment before forging Scratch test was conducted to measure the scratch resistance of unprocessed and MAF-processed samples. Dry sliding wear tests were performed on a tribometer (pin-on-disk) at ambient temperatures. MAF-processed materials exhibited better scratch and wear resistance compared to as-cast materials. After MAF, wear mechanisms in both alloys shifted from adhesive and delamination wear to a combination of abrasive and a lesser amount of adhesive wear. Moreover, the degree of delamination significantly decreased after MAF-process. Improved scratch and wear resistance is mainly due to increased microhardness via refinement and improved uniformity in the redistribution of eutectic silicon as well as the strain hardening of the aluminum phase. © ASM International 2023.
Effect of Samarium (Sm) Addition on Microstructure and Mechanical Properties of AA5083 Alloy
(Springer Science and Business Media Deutschland GmbH, 2024) Aravindh, G.; Kumar, G.V.P.; Udaya Bhat, K.
Researchers are interested in reaping the potential benefits of incorporating small amounts of rare earth elements into aluminum alloys to attain finer grain size and to improve mechanical properties like toughness. This research investigates the effects of samarium (Sm) addition at concentrations of 0.5%, 1.0%, and 1.5% by weight on the microstructural and mechanical properties of AA5083 alloy. Optical microscopy (OM), field emission gun scanning electron microscopy (FEGSEM), X-ray diffraction (XRD), tensile testing machine (UTM), Vickers microhardness testing, and Charpy instrumented impact test were employed to evaluate the microstructure and mechanical properties of both as cast and solution treated (ST) samples. The samarium (Sm) is a beneficial grain refiner, leading to tailored properties in the AA5083 alloy. The results indicate that adding 1 wt% Sm generated significant enhancements in mechanical properties, such as tensile strength increased by 236 MPa and an elongation of 13.1% with a 27% reduction in grain size. However, incorporating 1.5 wt% Sm had an adverse impact on material properties, such as the grain size of the material increased by 22.73% and reduction in the tensile strength by 31%, corresponding to 1 wt% Sm added AA5083 alloy. Impact energy was reduced with the addition of Sm to the AA5083 alloy, both in as cast and ST samples. Furthermore, fractography was performed after impact and tensile testing. © American Foundry Society 2023.
Enhancement of Microstructural, Mechanical, and Tribological Properties of AA5083 Alloy via Multi-axial Forging
(Springer, 2025) Aravindh, G.; Sahoo, B.; Kumar, G.V.P.; Udaya Bhat, K.
The present study investigates the influence of multi-axial forging (MAF) on the microstructure, mechanical, and wear properties of the AA5083 alloy. After solution treatment, the alloy was subjected to three MAF cycles at room temperature with a strain of 0.63 per cycle. The evolution of the microstructure was analyzed using optical microscopy, field emission gun scanning electron microscopy, and x-ray diffraction. Mechanical properties were evaluated through tensile testing, and Vicker’s micro-hardness and wear behavior of the alloys were investigated using reciprocating wear tests. The results demonstrated significant improvement in properties after the third MAF cycle, forming 8.3 ?m wide shear bands and a refined grain structure. The alloy achieved maximum hardness (130 HV), tensile strength (334 MPa), and elongation to failure (8.01%), along with a reduced strain-hardening exponent (0.27). Wear resistance showed marked enhancement, with wear volume reductions of 36%, 49%, and 21% under 1, 2, and 4 N loads, respectively. Similarly, wear rates decreased by 64%, 49%, and 15% under the same loads. These findings emphasize the MAF process's effectiveness in enhancing the mechanical and wear properties of AA5083 alloy, indicating its potential for advanced material processing techniques. © ASM International 2025.
Influence of Samarium (Sm) Addition on Mechanical and Tribological Performance of the Al–Mg Alloy AA5083
(Springer Science and Business Media Deutschland GmbH, 2025) Aravindh, G.; Sahoo, B.; Kumar, G.V.P.; Udaya Bhat, K.
Using rare earth elements as minor additives in aluminum alloys has become a promising strategy for enhancing their properties. This study specifically investigates the effects of introducing samarium (Sm) as a minor addition to the Al–Mg alloy AA5083 and analyzes the resulting changes after casting and subsequent solution treatment. The solution treatment process involved heating the alloy to 475 °C for 12 h, followed by rapid cooling in water. Various assessments, including compression testing, differential scanning calorimetry (DSC) analysis, and wear testing, were performed to evaluate the alterations of mechanical, thermal, and tribological characteristics. The results indicate that adding Sm significantly improves the mechanical strength, thermal stability, and wear resistance of the AA5083 alloy. Wear properties demonstrate that the AA5083 alloy with 1 wt.% Sm exhibited superior performance for both as-cast and solution-treated alloys compared to other alloys. These enhancements highlight the potential of incorporating rare earth microadditions to enhance the performance characteristics of aluminum alloys for a wide range of industrial applications. © American Foundry Society 2024.
Severe plastic deformation of Al-15Zn-2Mg alloy: Effect on wear properties
(2019) Manjunath, G.K.; Bhat, K.U.; Kumar, G.V.P.
In the present work, Al-Zn-Mg alloy having highest zinc content was deformed by one of the severe plastic deformation (SPD) technique, equal channel angular pressing (ECAP) and effect of ECAP on the microstructure evolution and the wear properties were studied. ECAP was performed in a split die and the channels of the die are intersecting at an angle of 120�. ECAP was attempted at least possible temperature and the alloy was successfully ECAPed at 423 K. Below this temperature samples were failed in the first pass itself. After ECAP, significant drop in the grain size was reported. Also, ECAP leads to significant raise in the microhardness of the alloy. Predominantly, after ECAP, upsurge in the wear resistance of the alloy was noticed. To figure out the response of ECAP on the wear properties of the alloy; worn surfaces of the wear test samples were analyzed in SEM. � 2019 Trans Tech Publications Ltd, Switzerland.