Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Has files: NoSubject: search.filters.subject.Grain refinement

Search Results

Now showing 1 - 10 of 71
  • No Thumbnail Available
    Item
    Effect of Rolling Reduction on Microstructure and Mechanical Properties Cu-3%Ti Alloy
    (Pleiades journals, 2019) Singh, P.; Ramesh, S.; Anne, G.; Shivananda Nayaka, H.
    Cu-3%Ti alloy is cold rolled with different reduction ratios and the microstructures and mechanical properties are compared with that of as-cast Cu-3%Ti alloy. Microstructure was analyzed using optical microscope and scanning electron microscope. Optical microscopy revealed significant grain refinement that occurred during the rolling process. Tensile test results indicate that the UTS is increased by a significant amount up to 80% rolling reduction. A significant amount of tensile strength increased up to 812 MPa is about 1.69 times that of the cast Cu-3%Ti alloy. Hardness of the rolled Cu-3%Ti increased as % reduction increased. Dimples were revealed on the fracture surface of the rolled Cu-3%Ti specimens indicating a ductile nature of the fracture. © 2019, Springer Nature Singapore Pte Ltd.
  • No Thumbnail Available
    Item
    A comparative study on the wear behavior of cast and forge aged A356 alloy with addition of grain refiner and/or modifier
    (Trans Tech Publications Ltd ttp@transtec.ch, 2014) Mallapur, D.G.; Sondur, D.G.; Udupa, K.R.
    In the present work, a comparative study on the wear behavior of cast aged and forge aged A356 alloy has been investigated without and with the addition of grain refiner and modifier, under dry sliding conditions using a pin-on-disc wear testing machine. The comparison study reveals that tribological properties of A356 materials are highly influenced by T6 heat treatment process. It is found in the present study that, cast aged A356 materials possess higher wear resistance as compared to forge aged materials. Apart from this, the study also reveals that cast aged material is associated with lower frictional forces and coefficient of friction as compared to the forge aged category. It is further observed in the present investigation that abrasive wear mechanism is operative in both the categories of the materials when tested with lower load for lower sliding speed and lower distance of run. At higher values of external parameters the adhesive wear mechanism dominates the wear process. Lower values of wear properties recorded by the forge aged material are an unexpected result in the present studies. It is conceived to be due to the presence of micro cracks while forging. © (2014) Trans Tech Publications, Switzerland.
  • No Thumbnail Available
    Item
    Microstructure and mechanical properties of magnesium alloy processed by equal channel angular pressing (ECAP)
    (Elsevier Ltd, 2017) Gopi, K.R.; Shivananda Nayaka, H.
    Equal Channel Angular Pressing (ECAP) with different passes was carried out for Mg-Al-Mn (AM) series magnesium alloy to investigate the microstructure and mechanical properties. ECAP process was carried up to 4 passes using route BC, where the samples are rotated by 90° in the same direction between consecutive passes. Microstructures were studied using optical microscope (OM) and scanning electron microscope (SEM) and it was observed that the grain size was reduced from 100 μm to 1 μm after 4 passes. Tensile test was conducted and the ultimate tensile strength (UTS) increased up to 2 passes but decreased with higher passes, even though grain size became finer with increase in ECAP passes. Microhardness was carried out and it was observed that the hardness was increased up to 2 passes of ECAP and decreased with higher passes. © 2017 Elsevier Ltd.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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).
  • No Thumbnail Available
    Item
    Electrochemical Behaviour of ECAP-Processed AM Series Magnesium Alloy
    (Springer International Publishing, 2019) Gopi, K.R.; Shivananda Nayaka, H.
    Equal channel angular pressing (ECAP) is a technique for inducing high strain into the material to achieve ultrafine grain refinement. AM80 magnesium was processed by ECAP with processing route BC. ECAP-processed samples were tested for microstructural studies and electrochemical measurements. Potentiodynamic polarization test revealed decrease in corrosion current density due to uniform refined microstructure of the processed samples. Increment in charge transfer resistance (Rt) was observed for ECAPed samples with increase in capacitive arc diameters in Nyquist plots showing increased corrosion resistance in comparison with as-cast condition. The increment in corrosion resistance is because of grain refinement and uniform dispersal of intermetallic particles, which improved development of protective layer and bonding due to increased grain boundary density by ECAP process. © 2019, The Minerals, Metals & Materials Society.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Item
    Effect of mushy state rolling on age-hardening and tensile behavior of Al-4.5Cu alloy and in situ Al-4.5Cu-5TiB2 composite
    (Elsevier Ltd, 2011) Siddhalingeshwar, I.G.; Herbert, M.A.; Chakraborty, M.; Mitra, R.
    The effect of mushy state rolling on aging kinetics of stir-cast Al-4.5Cu alloy and in situ Al-4.5Cu-5TiB2 composite and their tensile behavior in solution-treated (495°C) or differently aged (170°C) conditions, has been investigated. As-cast or pre-hot rolled alloy and composite samples were subjected to single or multiple mushy state roll passes to 5% thickness reduction at temperatures for 20% liquid content. Peak-aging times of mushy state rolled composite matrices have been found as ?7.5-10% of that of as-cast alloy. Such enhancement in aging kinetics is attributed to homogeneity in Cu atom distribution as well as increase in matrix dislocation density due to thermal expansion coefficient mismatch between Al and TiB2, matrix grain refinement and particle redistribution, achieved by mushy state rolling. Uniform precipitate distribution in mushy state rolled composite matrices leads to greater peak-age microhardness with higher yield and ultimate tensile strengths than those in as-cast alloy and composite. © 2010 Elsevier B.V.