Conference Papers
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Item Microstructural characterization and mechanical properties of cast Al-15Zn-2Mg alloy subjected to severe plastic deformation(Elsevier Ltd, 2018) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.In the present work, Al-15Zn-2Mg alloy was processed by ECAP technique for grain refinement. The ECAP processing was conducted at 150 °C. Microstructural characterization was carried out in OM, SEM, TEM and XRD. To evaluate the mechanical properties, hardness measurement and tensile tests were conducted at room temperature. Microstructural characterization showed that, ECAP processing leads to decrease in the grain size of the alloy. Also, small amount of dislocations were also observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was identified in the XRD analysis. The strength and the hardness values were increased after ECAP processing. After ECAP processing, microhardness of the material is increased from 173 Hv to 252 Hv and the UTS of the material is increased from 166 MPa to 362 MPa. After tensile testing, fracture surface of the cast material showed dendritic structure and the fracture surface of the ECAP processed material showed dimples. © 2018 Elsevier Ltd. All rights reserved.Item Effect of multi directional forging on impression creep behavior of Zn-24Al-2Cu alloy(Elsevier Ltd, 2018) Sharath, P.C.; Rajendra Udupa, K.; Preetham Kumar, G.V.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 μm 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.Item Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy(American Institute of Physics Inc. subs@aip.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; 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).Item Flow Properties of Cast Al-Zn-Mg Alloys Subjected to Equal Channel Angular Pressing(Institute of Physics Publishing helen.craven@iop.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.Flow stress can be described as the stress necessary to continue deformation at any stage of plastic strain. The strength coefficient (K) and strain-hardening exponent (n) are the two important flow properties of the material. In the present work, flow properties of three different cast Al-Zn-Mg alloys processed by equal channel angular pressing (ECAP) were investigated. ECAP processing was carried out in a die having Φ = 120° and Ψ = 30°. After ECAP processing, significant grain refinement and increase in the hardness was observed. Compression test was used to determine the flow properties of ECAP processed samples. Force-stroke data was recorded from the compression test. Flow curves were drawn by using force-stroke data. Strength coefficient and strain-hardening exponent were determined from the log-log plot of true stress-strain curves. Significant increase in the strength coefficient was observed after ECAP processing. Also, the strength coefficient is increased when the zinc content is increased in the alloy. Strain-hardening exponent was decreased with increase in the number of ECAP passes. © Published under licence by IOP Publishing Ltd.Item Effect of SiC Reinforcement on Microstructure and Mechanical Properties of Aluminum Metal Matrix Composite(Institute of Physics Publishing helen.craven@iop.org, 2018) Ajagol, P.; Anjan, B.N.; Marigoudar, R.N.; Preetham Kumar, G.V.Aluminum reinforced with silicon carbide composites areextensively used in automobile industries and aerospaceowing to their favourable microstructure and improved mechanical behaviour with respect to pure aluminium but at a lower cost. Aluminium is remarkable for the low density and its ability to resist corrosion. The aim of present study istoevaluate the mechanical and microstructural properties of aluminum with silicon carbide (average particle size 30-45μm) reinforced in varying weight percentages (wt %) ranging from 0-15 wt% in a step of 5% each. Ultimate tensile strength, micro hardness and density of the fabricated composites were investigated as a function of varying SiC wt%. Microstructure analysis was carried out on casted composites using optical microscopy and scanning electron microscopy. From micrographs it is clear that fair distribution of reinforcing particles in the matrix and also observed some clustering and porosity in the cast material. Results revealed that, the addition of SiC reinforcement in the aluminum matrix increases the hardness and ultimate tensile strength gradually from 23 HV to 47 HV and 84 MPa to 130 MPa respectively. © Published under licence by IOP Publishing Ltd.Item Workability Study on Austempered AISI 1018(Institute of Physics Publishing helen.craven@iop.org, 2018) Nagendhra, S.; Rami Reddy, A.S.; Preetham Kumar, G.V.Workability of a material is a complex technological concept that is related to both material and process characteristics. Austempering is a heat treatment process that is applied to ferrous metals, mostly steel and ductile iron. The present work was carried out to study the workability and the properties of AISI 1018 steel in austempering and annealing condition and then comparing with each other. Workability testing was carried out using collar type specimen by compressing it till the crack. Workability diagrams have been plotted as a function of axial and hoop strains at failure. The result shows that, the austempering process increases the tensile strength and hardness as well as the workability. Thus the austempering process has an effect on strength and hardness. © Published under licence by IOP Publishing Ltd.Item Severe plastic deformation of Al-15Zn-2Mg alloy: Effect on wear properties(Trans Tech Publications Ltd ttp@transtec.ch, 2019) Manjunath, G.K.; Bhat, K.U.; Preetham Kumar, G.V.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.Item Influence of sic and al2o3 particulate reinforcement on the mechanical properties of za27 metal matrix composites(Trans Tech Publications Ltd ttp@transtec.ch, 2019) Anjan, B.N.; Preetham Kumar, G.V.Zinc aluminum based matrix composites reinforced with SiC and Al2O3 particles have significant applications in the automobile field. Stir casting method followed by squeeze process was used for fabrication. ZA27 composites reinforced with SiC and Al2O3 particles (20-50µm) in various weight percentage (wt%) ranges from 0-10 in a step of 5 each was fabricated. OM, SEM and EDS analysis of microstructures obtained for matrix alloy and reinforced composites were performed in order to know the effect of varying wt% on physical and mechanical properties of composites. Squeeze casting technique shows better features such as fine microstructure as a result of low porosity and good bonding between matrix and reinforcement. Addition of reinforcements decreased the densities of matrix alloy. SiC reinforced composites showed better results as compared with Al2O3 reinforced ones. Hardness and ultimate tensile strength value of 10 wt% reinforced composites showed improved results. © 2019 Trans Tech Publications Ltd, Switzerland.Item Dry sliding wear behaviour of Al-5Zn-2Mg alloy processed by severe plastic deformation(Elsevier Ltd, 2019) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.Equal channel angular extrusion/pressing (ECAE/P) is an effectual technique to raise the mechanical, physical properties and resistance to wear of the materials. In this research, Al-5Zn-2Mg alloy material was ECAPed in route BC at lowest temperature. Hardness of the test material was increased after ECAE/P due to microstructure refinement. To demonstrate the wear characteristics of the Al-5Zn-2Mg alloy material after ECAE/P, wear tests (in dry sliding condition) were conducted at 2 conditions (condition 1: 19.62 N load and 1 m/s sliding speed, condition 2: 39.24 N load and 2 m/s sliding speed). The wear rate and magnitude of coefficient of friction (μ) were lessened after ECAE/P. Abrasive, adhesive and oxidation wear mechanisms are the predominant wear mechanisms noticed in the ECAE/P processed billets. Along with these mechanisms relocation of iron elements from the counter body (disc) to the test material was noticed. © 2019 Elsevier Ltd.Item Evolution of Tribological Properties of Cast Al–10Zn–2Mg Alloy Subjected to Severe Plastic Deformation(Springer Science and Business Media Deutschland GmbH, 2020) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.In the current investigation, tribological behaviour of the cast Al–10Zn–2Mg alloy processed by severe plastic deformation (SPD) technique was studied. In this work, one of the SPD techniques, equal channel angular pressing (ECAP) was adopted as a processing tool. ECAP was carried out in route BC and processing was attempted at the lowest temperature. After ECAP, grain structure of the material was refined and considerable improvement in the microhardness of the alloy was perceived. Mainly, wear resistance of the alloy material was enhanced with successive ECAP passes. Coefficient of friction of the alloy material was decreased with successive ECAP passes. Wear resistance of the alloy was decreased with a rise in the applied load and the sliding speed. Both at low and high load condition, abrasive wear was noticed in as-cast and homogenized specimens. Whereas in ECAPed specimens, in addition to abrasive wear, oxidation wear and adhesive wear were observed in low load and it changes to abrasive wear at high load. In the ECAPed specimens, at low load transfer of iron particles from the steel disc surface to the specimen surface was identified. © 2020, Springer Nature Singapore Pte Ltd.