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Item Influence of Multi Axial Forging (MAF) on Microstructure and Mechanical Properties of Cu-Ti Alloy(Elsevier Ltd, 2018) Ramesh, S.; Shivananda Nayaka, H.S.; Gopi, K.R.Multi axial forging (MAF) is one among the severe plastic deformation (SPD) processes, where large strains are imposed into the component. In the present work, as-received Cu-1.5%Ti alloy was subjected to MAF for 2 and 4 cycles at room temperature. Microstructure showed grain refinement after 2 and 4 cycles. Average grain size obtained for MAF processed samples after 2 and 4 cycles are 120 μm and 40 μm, respectively compared to initial grain size of 800 μm. The Mechanical properties were analyzed for as-received and MAF processed samples. Tensile test showed increased ultimate tensile strength (493 MPa) for MAF 4-cycle sample compared to as-received (191 MPa) condition with accumulated strain of 2.18 for 4 cycles. Increase in hardness was observed for MAF processed sample of 143 Hv for 4-cycle compared to as-received sample of 67 Hv. © 2018 Elsevier Ltd.Item Influence of cold rolling process on microstructure and mechanical properties of Cu-1.5%Ti alloy(American Institute of Physics Inc. subs@aip.org, 2018) Ramesh, S.; Shivananda Nayaka, H.S.; Anne, G.; Gopi, K.R.The effects of cold rolling on the microstructure evolution and mechanical properties of Cu-1.5%Ti alloy were investigated. The results showed that the tensile strength of the Cu-1.5%Ti alloy increased with an increase of rolling deformation at room temperature. Significant grain refinement took place during rolling process revealed in optical microstructure and transmission electron microscope analysis. XRD patterns revealed peaks indexed to Cu, Cu3-Ti2 and Cu4-Ti3 after 8-pass rolling process. Microhardness of the rolled Cu-1.5%Ti alloy layers increased incessantly with increase in the number of rolling passes. Tensile strength increased up to 294 MPa which was about 1.54 times higher than that of the cast Cu-1.5%Ti alloy. Fracture surfaces of the rolled Cu-1.5%Ti alloy revealed the dimples in the structure, which is an indication of ductile fracture. © 2018 Author(s).Item A review on wrought magnesium alloys processed by equal channel angular pressing(Inderscience Publishers, 2015) Muralidhar, M.; Narendranath, S.; Shivananda Nayaka, H.S.Magnesium and its alloys with severe plastic deformation (SPD) techniques are more attractive as structural parts in many industrial applications because of their advantages. In this paper, the importance of wrought magnesium alloys with their applications to accomplish the essential development of components is reviewed. In addition, the different approaches of equal channel angular pressing (ECAP) process for refining the grain size to achieve the ultrafine grained material on the bulk metals are discussed. Recent developments in the ECAP process are outlined clearly with their importance to overcome many complexities. Various factors like processing temperature of a specimen, die geometry, ram speed, back pressure and processing routes influencing during ECAP process of wrought magnesium alloys at different conditions such as channel angle and corner or outer arc angle are discussed. Finally, the properties of ECAP processed wrought alloys are outlined for improving the microstructure in structural parts. © © 2015 Inderscience Enterprises Ltd.Item Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Gopi, K.R.; Shivananda Nayaka, H.S.; Sahu, S.Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing. © 2016, ASM International.Item Microstructural Evolution and Strengthening of AM90 Magnesium Alloy Processed by ECAP(Springer Verlag, 2017) Gopi, K.R.; Shivananda Nayaka, H.S.; Sahu, S.Equal-channel angular pressing (ECAP) was applied on AM90 magnesium alloy using processing route B C at 275?C up to four passes. Microstructural evolution and the corresponding modification in mechanical properties (strength, elongation and hardness) corresponding to the number of ECAP passes were evaluated using X-ray diffraction (XRD), electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, tensile test and microhardness test. Shear deformation was found to refine the microstructure by breaking it into smaller grains formed by dislocation reconstruction. Tensile strength and hardness were found to increase by ? 128 and 23%, respectively, for ECAP-processed 2-pass sample in comparison with that of the homogenized condition. After two passes, tensile strength and hardness started decreasing even though the grain size was still decreasing, which was found to be associated with texture modification during ECAP processing as observed by XRD analysis. © 2017, King Fahd University of Petroleum & Minerals.Item Effect of multiaxial cryoforging on microstructure and mechanical properties of a Cu-Ti Alloy(Institute of Physics Publishing helen.craven@iop.org, 2019) Ramesh, S.; Shivananda Nayaka, H.S.; Gopi, K.R.; Sahu, S.Cu-Ti alloy, processed by multiaxial forging (MAF) at cryogenic temperature with a cumulative strain up to 1.64, was investigated for microstructure and mechanical properties. The deformed microstructures were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average grain size of 2 ?m was achieved in the deformed sample after 3 cycles of MAF. TEM studies indicated that the shear bands width of the deformed sample after 3 cycles reduced to 1 ?m. Tests for mechanical properties indicated an increase in tensile strength and hardness and it was found to be correlated with an increase in dislocation density and grain boundary strengthening mechanism. Ultimate tensile strength (UTS) of 390 MPa, 480 MPa, and 590 MPa was observed in MAF processed samples after 1, 2, and 3 cycles, respectively. Hardness increased from 65 Hv (as-received) to 240 Hv after 3 cycles of MAF. Fractography analysis showed that, with an increase in number of MAF cycles, dimple size reduced up to 1 cycle and percentage elongation increased after 2 cycles of MAF. © 2018 IOP Publishing Ltd.Item Influence of Multidirectional Forging on Microstructural, Mechanical, and Corrosion Behavior of Mg-Zn Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.S.; Sahu, S.; Ramesh, M.R.Multidirectional forging (MDF) was applied to Mg-6%Zn alloy up to 5 passes successfully at 280 °C. MDF-processed materials were characterized using optical microscope, scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and x-ray diffraction. Obtained results showed a significant reduction in grain size (up to 3.8 ?m) having a large fraction of high-angle grain boundaries after 5 passes of MDF process. Maximum tensile strength of 230 MPa was achieved for 5-pass MDF-processed Mg-6%Zn alloy which is about ~ 2.0 times higher in comparison with that of homogenized alloy (117 MPa) and was attributed to higher dislocations density and grain refinement. Corrosion behavior of the alloy was investigated in 0.1 M NaCl solution using potentiodynamic polarization test, electrochemical impedance spectra analysis, and immersion tests. It was found that the corrosion rate of 5-pass MDF sample improved (0.34 mm/year) ~2.5 times in comparison with that of homogenized Mg-6%Zn alloy (0.86 mm/year) due to fine grain structure, which creates more grain boundaries that act as a corrosion barrier. © 2019, ASM International.Item Influence of equal channel angular pressing and laser shock peening on fatigue behaviour of AM80 alloy(Elsevier B.V., 2019) Praveen, T.R.; Shivananda Nayaka, H.S.; Swaroop, S.AM80 magnesium alloy was processed with Equal Channel Angular Press (ECAP)for grain refinement. Laser shock peening without coating (LSPwC)were executed on ECAP processed sample at 8 GW cm?2 and further grain refinement were observed at surface. SEM image expose the grain refinement at different stage of processing, and fine grains of sub-micron size were observed at surface level after ECAP + LSPwC. Residual stress were measured using X-ray diffraction, sin2(?)method and compressive residual stress was found after ECAP. LSPwC intensify the compressive residual stress at surface. Increases in magnitude of residual stresses were noticed with 200 and 300% of LSPwC. Increase in surface roughness were noticed from 0.6 to 6.8 ?m by increasing the percentage of LSPwC coverage. Fatigue tests were acknowledged the effect of ECAP and ECAP + LSPwC on reliability of grain refinement technique. ECAP sample showed fatigue life of 7539 cycles against as received. Highest fatigue life of 85,268 life cycles was observed with ECAP + LSPwC by 100% of coverage. Further process of LSPwC for 200 and 300%, fatigue life was significantly decreases to 22,987 and 384 cycles respectively. SEM images of fractured surface exhibits effect of ECAP and LSPwC on crack initiation and propagation for failure. © 2019 Elsevier B.V.Item Investigation of Tribological Characteristics of Cu-Ti Alloys Processed by Multi-Axial Cryo-Forging(Springer, 2022) Ramesh, S.; Shivananda Nayaka, H.S.; Anne, G.; Arun, M.N.; Naik, G.M.Cu-XTi alloys (X = 1.5 and 4.5%) were subjected to multi-axial forging (MAF) under cryogenic condition up to three passes successfully. Characteristics of the MAF-processed alloys were analyzed using microstructural analysis, hardness and wear tests. Worn surface morphology and elemental analysis was performed by scanning electron microscopy. The hardness of samples increases with higher MAF passes due to strain hardening and grain refinement. Wear test was done for six various sliding distances (500, 1000, 1500, 2000, 2500 and 3000 m), two different loads (10 and 20 N), and two different velocities (1 and 2 m/s) using the pin-on-disk wear test rig. Wear loss of as-received samples is higher than MAF-pressed samples due to an increase in hardness, but wear loss increases as the load increases. Coefficient of friction is reduced with the increase in MAF pass, which is due to strain hardening effect. The worn surface exhibits the plastic deformation regions, delamination, plowing and formation of oxide layers, which was revealed by energy-dispersive X-ray spectroscopy analysis. Also, MAF-processed samples exhibited abrasive wear mechanism as a result of formation of oxygen layer as revealed in SEM micrographs. © 2022, ASM International.Item Microstructural Study and Mechanical Characterization of ECAP Processed C70600 Alloy(Springer, 2022) Sachin, S.; Shivananda Nayaka, H.S.Copper–Nickel alloy C70600 was processed by equal channel angular pressing (ECAP), at room temperature, up to 8 passes, to study the mechanical properties and metallurgical behavior Microstructural studies showed grain refinement up to fourth ECAP pass. Microhardness value increased by 45% after 4 ECAP passes. With further increase in ECAP passes, samples attained a saturated state. Similar trend was observed in Ultimate tensile strength with an increase of 54% as compared to homogenized sample and reached a maximum value of 562 MPa. Increase in mechanical property was attributed to strengthening by grain refinement and dislocation strengthening. XRD analysis showed the absence of precipitate in the deformed specimens. © 2022, The Institution of Engineers (India).